Chronic obstructive pulmonary disease: Diagnosis and staging

INTRODUCTION — Chronic obstructive pulmonary disease (COPD) is a common respiratory condition characterized by cough, dyspnea, and airflow limitation [1]. Approximately 10 percent of individuals aged 40 years or older have COPD, although the prevalence varies between countries and increases with age [1-4]. COPD is consistently ranked among the top causes of death in the United States, killing more than 120,000 individuals each year [5,6]; prior to the COVID-19 (coronavirus disease 2019) pandemic, it was the third leading cause worldwide [7]. As a consequence of its high prevalence and chronicity, COPD causes high resource utilization with frequent clinician office visits, multiple hospitalizations due to acute exacerbations, and the need for chronic therapy [8].

Establishing a correct diagnosis of COPD is important because appropriate management can decrease symptoms (especially dyspnea), reduce the frequency and severity of exacerbations, improve health status, improve exercise capacity, and prolong survival [9]. Many health conditions in older adults can result in dyspnea or cough, so respiratory symptoms should not be attributed to COPD without appropriate evaluation and diagnosis.

The definition, clinical manifestations, diagnostic evaluation, and staging of COPD are discussed here. The risk factors, natural history, prognosis, and treatment of COPD are discussed separately.

●(See "Chronic obstructive pulmonary disease: Risk factors and risk reduction".)

●(See "Chronic obstructive pulmonary disease: Prognostic factors and comorbid conditions".)

●(See "Stable COPD: Overview of management".)

●(See "COPD exacerbations: Clinical manifestations and evaluation".)

●(See "COPD exacerbations: Management".)

DEFINITIONS — COPD should be understood in the context of other closely related common respiratory conditions (emphysema, chronic bronchitis, and chronic obstructive asthma) that represent an overlapping spectrum of airway diseases.

COPD — The Global Initiative for Chronic Obstructive Lung Disease (GOLD), a project initiated by the National Heart, Lung, and Blood Institute (NHLBI) and the World Health Organization (WHO), defines COPD as a "heterogeneous lung condition characterized by chronic respiratory symptoms (dyspnea, cough, expectoration, exacerbations) due to abnormalities of the airway (bronchitis, bronchiolitis) and/or alveoli (emphysema) that cause persistent, often progressive, airflow obstruction" [1,10].

In practice, the diagnosis of COPD requires all of the following (see 'Diagnosis' below):

●The presence of pulmonary symptoms (dyspnea, cough, or sputum production)

●The appropriate clinical context (most notably but not exclusively tobacco exposure) (table 1)

●Evidence of airflow limitation

Chronic bronchitis — Chronic bronchitis is defined as a chronic productive cough over a defined period, classically for at least three months in each of two successive years, in a patient in whom other causes of chronic cough (eg, bronchiectasis) have been excluded [1]. It may precede or follow development of airflow limitation [1,11,12]. This definition has been used in many studies, despite the arbitrarily selected symptom duration. By age 35 to 40 years, cigarette smokers may develop chronic bronchitis and start to have intermittent exacerbations of their symptoms even in the absence of airflow obstruction [13].

Emphysema — Emphysema describes enlargement of the airspaces distal to the terminal bronchioles that is accompanied by destruction of the airspace walls, a pathologic finding frequently seen in patients with COPD [14]. This finding manifests clinically with decreased breath sounds and evidence of hyperinflation of the lungs on examination or imaging; it is frequently associated with dyspnea. Emphysema is classically not accompanied by macroscopic fibrosis. While emphysema can exist in individuals who do not have airflow limitation, it is more common among patients who have moderate or severe airflow obstruction [1,15-17].

The various subtypes of emphysema (eg, proximal acinar, panacinar, distal acinar) are described below. (See 'Pathology' below.)

Airflow limitation — Airflow limitation is physiologically defined as an abnormally reduced ability to exhale efficiently. The severity and presence of airflow limitation are determined by evaluating the forced expiratory volume in one second (FEV₁) and the ratio of the FEV₁ to the total forced expiratory volume (aka, forced vital capacity [FVC]). (See 'Spirometry' below and "Office spirometry", section on 'Interpretation'.)

Airflow limitation may be fixed or may change in response to exogenous factors (eg, environmental exposure, temperature, and medications). Asthma is defined by significant variability in airflow obstruction, whereas COPD is characterized by obstruction that is not fully reversible with medication.

Asthma — The Global Initiative for Asthma (GINA) gives the following definition of asthma: "Asthma is a chronic inflammatory disorder of the airways that leads to recurrent episodes of wheezing, breathlessness, chest tightness, and coughing. These episodes are associated with widespread, but variable, airflow obstruction that is often reversible either spontaneously or with treatment" [1]. The episodic nature of the symptoms and reversibility of airflow obstruction are clinical features that help distinguish asthma from COPD. However, adults with longstanding asthma may develop persistent airflow limitation. Distinguishing these patients from those with COPD is difficult, particularly in the context of additional COPD risk factors (table 1).

Interrelationships among these conditions — Chronic bronchitis and emphysema were previously incorporated into the definition of COPD [18,19], and their clinical features overlap those of patients with asthma and COPD. This has caused considerable confusion regarding appropriate classification of patients with respiratory symptoms and COPD risk factors. Important points about these interrelationships include:

●COPD – Patients with emphysema or chronic bronchitis and persistent postbronchodilator airflow limitation meet the definition of COPD. Chronic bronchitis, emphysema, and postbronchodilator airflow limitation commonly occur together [20].

●Asthma – Patients with asthma who only have inducible airway obstruction or whose airflow limitation is completely reversible with bronchodilator therapy are not considered to have COPD.

●Asthma and COPD – Patients with asthma whose airflow limitation does not remit completely and who have other appropriate clinical risk factors (eg, older age, exposure history) are considered to have both asthma and COPD. The etiology and pathogenesis of COPD in such patients may be different from that of other COPD patients (table 2). While descriptors "asthma and COPD overlap (ACO)" and "COPD-A" have been proposed to identify patients with airway disease who have features of both asthma and COPD, the topic remains controversial. No single, universally accepted definition has emerged. Central to most of the proposed definitions are age >40 years, history of asthma at a younger age, persistent postbronchodilator airflow obstruction, and evidence of partial bronchodilator reversibility. (See "Asthma and COPD overlap (ACO)".)

Further study of this relationship will be needed to determine with certainty how treatment algorithms should be tailored to these patients [21,22]. An evolving literature suggests differential responses to inhaled glucocorticoids in patients with or without increased circulating eosinophils [23,24]. Peripheral eosinophilia is recommended by GOLD and our authors for use clinically to guide pharmacotherapy in all patients with COPD. (See "Stable COPD: Follow-up pharmacologic management", section on 'Blood eosinophils, inhaled corticosteroids, and exacerbations'.)

Subgroups of COPD patients with eosinophilia may experience clinical improvement with biologic medications shown to have benefit in asthma. (See "Stable COPD: Follow-up pharmacologic management", section on 'Future directions' and "Management of refractory chronic obstructive pulmonary disease", section on 'Frequent exacerbations despite azithromycin or roflumilast'.)

●Pre-COPD – Patients with chronic bronchitis or emphysema without irreversible airway obstruction do not have COPD but are at high risk for developing the disease [25,26]. The term "pre-COPD" is used to identify such individuals who have either respiratory symptoms, radiographic abnormalities consistent with COPD, or early lung function changes in the context of COPD risk factors but do not have airway obstruction as defined by FEV₁/FVC <0.7. There is not full consensus on the defining features of pre-COPD, but diagnostic criteria have been proposed (table 3) [1,27,28].

Epidemiologic studies suggest that nearly 50 percent of current and former smokers without airway obstruction have respiratory symptoms, which correlate with reduced exercise capacity, radiographic emphysema and wall thickening, and lung function at the lower end of the normal range [16,17]. Those with borderline airway obstruction (FEV₁/FVC <0.75), greater smoking history, and chronic bronchitis have an increased likelihood of subsequent COPD diagnosis [29].

While many of these "pre-COPD" patients are treated off-label with bronchodilators or inhaled glucocorticoids, one large trial failed to show improvement in respiratory symptoms or quality of life with dual long-acting bronchodilator therapy (indacaterol-glycopyrrolate) versus placebo in this population [30]. Hence, existing evidence does not support inhaled bronchodilator therapies for symptomatic patients without airway limitation. Additional study is needed to determine appropriate preventative and maintenance therapies for this population.

●Other airway diseases – Patients with airflow limitation due to diseases that have a known etiology or a specific pathology (eg, cystic fibrosis, bronchiectasis, obliterative bronchiolitis) are not considered to have COPD. However, these exclusions are loosely defined [31].

PATHOLOGY — Histology is not obtained from patients with COPD as part of the diagnostic work-up. The predominant pathologic changes of COPD are found in the airways, but changes are also seen in the lung parenchyma and pulmonary vasculature. In a given individual, the pattern of pathologic changes depends on features of the underlying disease (eg, chronic bronchitis, emphysema, alpha-1 antitrypsin deficiency), genetic susceptibility, and disease severity [1]. While radiographic methods do not have the resolution of histology, high-resolution computed tomography (HRCT) can assess lung parenchyma [32], airways [33], and pulmonary vasculature [34]. (See 'Additional testing' below.)

Pathologic features of COPD (by compartment) include:

●Airways – In the airways, COPD results in chronic inflammation, increased numbers of goblet cells, mucus gland hyperplasia, fibrosis, as well as narrowing in and loss of small airways. In addition, airway collapse frequently occurs due to the loss of tethering caused by emphysematous destruction of alveolar walls [15]. Among patients with chronic bronchitis who have mucus hypersecretion, an increased number of goblet cells and enlarged submucosal glands are typically seen.

Chronic airway inflammation in chronic bronchitis and emphysema is frequently characterized by the presence of CD8+ T-lymphocytes, neutrophils, and CD68+ monocytes/macrophages (picture 1) [35-39]. In comparison, the bronchial inflammation of asthma is more often characterized by the presence of CD4+ T-lymphocytes, eosinophils, and increased interleukin (IL)-4 and IL-5 [40-42]. These findings are not diagnostic, however, as there can be significant overlap between these inflammatory airway phenotypes in individual patients.

●Lung parenchyma – Emphysema affects the structures distal to the terminal bronchiole, consisting of the respiratory bronchiole, alveolar ducts, alveolar sacs, and alveoli, known collectively as the acinus. These structures in combination with their associated capillaries and interstitium form the lung parenchyma. The part of the acinus that is affected by permanent dilation or destruction determines the subtype of emphysema.

•Proximal acinar (also known as centrilobular) emphysema refers to abnormal dilation or destruction of the respiratory bronchiole, the central portion of the acinus. It is commonly associated with cigarette smoking and is the most common emphysema subtype seen in patients with COPD. Centrilobular emphysema is also seen in coal workers’ pneumoconiosis.

•Panacinar emphysema refers to enlargement or destruction of all parts of the acinus. Diffuse panacinar emphysema is a characteristic of alpha-1 antitrypsin deficiency, although it can be seen in combination with proximal acinar emphysema in other patients with COPD. (See "Clinical manifestations, diagnosis, and natural history of alpha-1 antitrypsin deficiency".)

•In distal acinar (also known as paraseptal) emphysema, the alveolar ducts are predominantly affected. Distal acinar emphysema may occur alone or in combination with proximal acinar and panacinar emphysema. When it occurs alone, extensive subpleural paraseptal emphysema may be associated with spontaneous pneumothorax, but it is otherwise of little clinical significance. (See "Pneumothorax in adults: Epidemiology and etiology".)

●Pulmonary vasculature – Changes in the pulmonary vasculature in COPD include intimal hyperplasia and smooth muscle hypertrophy/hyperplasia, which are thought to be due to chronic hypoxic vasoconstriction of the small pulmonary arteries [43].

CLINICAL PRESENTATION

Symptoms and pattern of onset — The three cardinal symptoms of COPD are dyspnea, chronic cough, and sputum production; the most common early symptom is exertional dyspnea. Less common symptoms include wheezing and chest tightness (table 4A). However, any of these symptoms may develop independently and with variable intensity.

There are various ways in which patients with COPD present [44]:

●Patients who have an extremely sedentary lifestyle but few complaints – These patients require careful questioning to elicit a history that is suggestive of COPD. Some patients unknowingly avoid exertional dyspnea by shifting their expectations and limiting their activity. They may be unaware of the extent of their limitations or that their limitations are due to respiratory symptoms, although they may complain of fatigue.

●Patients who present with progressive dyspnea and chronic cough – For these patients, dyspnea may initially be noticed only during exertion. However, it eventually becomes noticeable with progressively less exertion or even at rest. The chronic cough is characterized by the insidious onset of sputum production, which occurs in the morning initially but may progress to occur throughout the day. The daily sputum volume rarely exceeds 60 milliliters. The sputum is usually mucoid but becomes more purulent during exacerbations.

●Patients who present with intermittent pulmonary symptoms and signs – These patients have minimal symptoms at baseline but episodically develop some of the following: cough, purulent sputum, wheezing, fatigue, and dyspnea. Typically, the interval between exacerbations decreases as the severity of the COPD increases. This symptom complex can be a diagnostic challenge due to overlap with other common chronic diseases. For example, the combination of intermittent wheezing and dyspnea may lead to an incorrect diagnosis of asthma. Conversely, other illnesses with similar episodic manifestations (eg, heart failure, bronchiectasis, bronchiolitis) are often incorrectly diagnosed as a COPD exacerbation (table 5). (See "COPD exacerbations: Management".)

Approximately 62 percent of patients with moderate to severe COPD report variability in symptoms (eg, dyspnea, cough, sputum, wheezing, or chest tightness) over the course of the day or week to week; morning is typically the worst time of day [45].

Patients with COPD may experience weight gain (due to activity limitations), weight loss (possibly due to dyspnea while eating or increased metabolic work of breathing), limitation of activity (including sexual), cough, syncope, or feelings of depression or anxiety. Weight loss generally reflects more advanced disease and is associated with a worse prognosis.

Comorbid diseases that may accompany COPD include lung cancer, bronchiectasis, cardiovascular disease, osteoporosis, metabolic syndrome, skeletal muscle weakness, anxiety, depression, and cognitive dysfunction. Patients may also report a family history of COPD or other chronic respiratory illness [1,46-51].

Risk factors, including smoking and inhalational exposures — For patients presenting with respiratory symptoms, it is critical to assess for the genetic, developmental, and environmental risk factors that can predispose to the development of COPD (table 4A) [1,27,52]. The increasing recognition of these varying risk factors beyond smoking alone have led to a proposed taxonomy of COPD "etiotypes" (table 2). Understanding the predominant etiology of disease in a given patient may allow for more targeted risk reduction. A more complete discussion of COPD risk factors and risk reduction can be found elsewhere. (See "Chronic obstructive pulmonary disease: Risk factors and risk reduction".)

The most common risk factor for COPD is cigarette smoking. Other exposures including passive smoke and biomass fuel use also play significant roles worldwide [1,53,54].

●Smoking history – The amount and duration of smoking contribute to disease severity [1,55-57]. Thus, a key step in the evaluation of patients with suspected COPD is to ascertain the number of pack-years smoked (packs of cigarettes per day multiplied by the number of years). A smoking history should include the age of starting and the age of quitting, as patients may underestimate the number of years they smoked. With enough smoking, almost all smokers will develop measurably reduced lung function [9]. While studies have shown an overall "dose-response curve" for smoking and lung function, some individuals develop severe disease with fewer pack-years and others have minimal to no symptoms despite many pack-years [9].

The exact threshold for the duration/intensity of cigarette smoking that will result in COPD varies from one individual to another. In the absence of an additional genetic/environmental/occupational predisposition, smoking less than 10 to 15 pack-years of cigarettes is unlikely to result in COPD.

●History of fume and dust exposure – The environmental/occupational history may disclose other important risk factors for COPD, such as exposure to fumes or organic or inorganic dusts, including household biomass smoke. These exposures help to explain the significant minority of patients with COPD who never smoked [55,58,59].

●Other risk factors – Certain pulmonary and systemic infections are known to cause permanent structural changes in the lung that predispose to COPD. In particular, childhood pneumonias, tuberculosis infection, and human immunodeficiency virus (HIV) are associated with high risk for later development of COPD [52]. Similarly, premature birth and early-life asthma may affect the development of the lung and increase the risk of COPD. A history of asthma is also important to elicit because poorly controlled asthma in adulthood may progress to fixed airflow limitation and COPD [58,60]. A strong family history of COPD or other chronic respiratory illnesses, particularly early in life, may suggest a genetic predisposition to COPD.

Physical examination — The findings on physical examination of the chest vary with COPD severity (table 4A-B). (See 'Assessment of severity and staging' below.)

●Mild disease – In mild disease, the physical examination may be normal. Subtle clues include prolonged expiratory time and faint end-expiratory wheezes on forced exhalation.

●Moderate to severe disease – As the severity of the airway obstruction increases, physical examination may reveal hyperinflation (eg, increased resonance to percussion), decreased breath sounds, wheezes, crackles at the lung bases, and/or distant heart sounds [61]. Features of severe disease include an increased anteroposterior diameter of the chest ("barrel-shaped" chest) and a depressed diaphragm with limited movement based on chest percussion.

●End-stage disease and chronic respiratory failure – Patients with end-stage COPD may adopt positions that relieve dyspnea, such as leaning forward with arms outstretched and weight supported on the palms or elbows. This posture may be evident during the examination or may be suggested by the presence of callouses or swollen bursae on the extensor surfaces of forearms. Other physical examination findings include use of the accessory respiratory muscles of the neck and shoulder girdle, expiration through pursed lips, paradoxical retraction of the lower interspaces during inspiration (ie, Hoover sign) [62,63], cyanosis, asterixis due to severe hypercapnia, and an enlarged, tender liver due to right heart failure. Neck vein distention may also be observed because of increased intrathoracic pressure, especially during expiration.

●Adjunctive signs – Yellow stains on the fingers due to nicotine and tar from burning tobacco are a clue to ongoing and heavy cigarette smoking [64]. Clubbing of the digits is not typical in COPD (even with associated hypoxemia). Its presence suggests comorbidities such as lung cancer, interstitial lung disease, or bronchiectasis.

DIAGNOSTIC EVALUATION

Whom to evaluate — Further diagnostic evaluation for COPD is appropriate in adults who report dyspnea, chronic cough, or chronic sputum production, or who have had a gradual decline in activity level, particularly if they have risk factors for COPD (eg, cigarette smoking, indoor biomass smoke) (table 4A) [1,56]. Adults without any symptoms should not undergo further testing for COPD. (Related Pathway(s): Chronic obstructive pulmonary disease: Initial diagnosis.)

Some patients with significant symptomatic COPD fail to report these symptoms to physicians. We agree with the Global Initiative for Chronic Obstructive Lung Disease (GOLD) in advocating for active case finding among at risk individuals [1]. The CAPTURE questionnaire (Chronic obstructive pulmonary disease Assessment in Primary care To identify Undiagnosed Respiratory disease and Exacerbation risk) is a well-validated tool that can help identify occultly symptomatic patients who would likely benefit from therapy for COPD and would therefore be candidates for diagnostic evaluation using spirometry (table 6) [65,66]. Notably, in one large trial of its use as a screening tool for clinically significant COPD in a primary care population, the CAPTURE questionnaire exhibited a sensitivity 48 percent, specificity 89 percent, positive predictive value 10 percent, and number needed to screen of 82 [67].

Based both on the post hoc analysis of results from the CAPTURE screening trial [67] and the increased emphasis on symptoms rather than airflow limitation as a driver of therapeutic strategies [1], use of CAPTURE without peak flow measurements may identify patients appropriate for further evaluation and therapy. Patients with a questionnaire score of 0 to 2 are at lower risk, whereas those with scores 3 to 6 should undergo spirometric evaluation.

Current guidelines do not support population-based screening of asymptomatic adults for COPD with spirometry [68,69], as asymptomatic mild airflow obstruction does not require treatment [56,69]. Asymptomatic and nonsmoking individuals with mild airflow obstruction but no history of asthma do not have the same progressive decline in lung function that is observed among individuals who have a similar degree of airflow obstruction and are symptomatic or continue to smoke [70].

How to evaluate — Patients at risk for COPD should be evaluated with spirometry; we also typically obtain laboratory testing for dyspnea (eg, complete blood count, thyroid-stimulating hormone, N-terminal pro hormone brain natriuretic peptide [BNP]) and a chest radiograph to assess for other cardiac and pulmonary conditions.

Spirometry — Spirometry is required to establish the diagnosis of COPD. When evaluating a patient for possible COPD, we typically perform spirometry before and after bronchodilator administration to determine whether airflow limitation is present and whether it is partially or fully reversible. Airflow limitation that is irreversible or only partially reversible with bronchodilator treatment is a defining physiologic feature of COPD. Patients without airflow limitation on prebronchodilator spirometry are highly unlikely to have COPD. (See "Office spirometry", section on 'Post-bronchodilator spirometry'.)

The most important values measured during spirometry are the forced expiratory volume in one second (FEV₁) and the forced vital capacity (FVC). The postbronchodilator ratio of FEV₁/FVC determines whether nonreversible airflow limitation is present [1]; the postbronchodilator percent predicted value for FEV₁ determines the severity of airflow limitation (algorithm 1). The ratio of FEV₁/FVC is not used to determine severity of airflow limitation because FVC often decreases with increasing obstruction due to air trapping or premature termination of exhalation.

An abnormal postbronchodilator FEV₁/FVC ratio has traditionally been thought to be more reliable than prebronchodilator measurements. However, several cohort studies have demonstrated that prebronchodilator values are reproducible [71], and that obstruction only found on postbronchodilator measurements (due to a preferential FVC response to bronchodilator) is less common [72]. We agree with GOLD that prebronchodilator FEV₁/FVC alone may acceptably be used as an initial test to determine the presence of airflow limitation [1]. Those without airflow limitation on prebronchodilator testing are unlikely to have COPD and do not require bronchodilator administration to further exclude the diagnosis. In contrast, those with prebronchodilator airflow limitation should undergo postbronchodilator testing to establish the diagnosis of COPD.

Patients with significant smoking exposure and abnormal prebronchodilator FEV₁/FVC, but normal postbronchodilator FEV₁/FVC, do not meet diagnostic criteria for COPD; however, they are at high risk for developing COPD. Such patients comprised 6 percent of former or current heavy smokers in one cohort [73]. Compared with smokers without prebronchodilator obstruction, these patients had a higher likelihood of progression to COPD (hazard ratio [HR] 6.2, 95% CI 4.6-8.3), with 61 percent (versus 14 percent) progressing to COPD within five years [73]. We reassess this group of patients with repeat spirometry after one year, or earlier if they have worsening symptoms.

●Threshold for airflow limitation – The ideal threshold for establishing airflow limitation in the diagnosis of COPD has not been empirically determined. We agree with the GOLD recommendations, which support the simple and well-established use of postbronchodilator FEV₁/FVC <0.7 as the threshold for nonreversible airflow limitation [1].

However, the FEV₁/FVC ratio decreases with age, so use of the fifth percentile lower limit of normal (LLN) of the FEV₁/FVC ratio (or, equivalently, a z-score of -1.645) rather than the absolute value of <0.7 has been advocated by some as a dividing point for the diagnosis of COPD and other obstructive lung diseases [74-79]. In practice, the adverse consequences of overdiagnosis of COPD in the elderly by use of a fixed ratio are somewhat mitigated by checking spirometry only in patients with symptoms and risk factors for COPD, but underdiagnosis of younger persons with abnormal airflow for age remains a concern. (See "Office spirometry", section on 'Ratio of FEV1/FVC' and "Selecting reference values for pulmonary function tests", section on 'Spirometry'.)

One large study pooling data from nearly 25,000 adults in population-based cohorts found that a fixed threshold of 0.7 was nearly optimal for determining persons at increased risk for COPD hospitalization or death, performing slightly better than LLN [80]. However, an analysis of current and former smokers with airflow limitation based on GOLD criteria but normal lung function based on LLN found that these patients had normal measures of multiple other respiratory-related phenotypes, including CT-measured emphysema and gas trapping [81].

Evidence from one United States cohort of middle-aged ever-smokers demonstrated that Black participants without airway obstruction had disproportionately lower FVCs (and hence higher FEV₁/FVC ratios) than age- and sex-matched White participants without airway obstruction, a finding which correlated with more significant symptoms despite the absence of spirometrically defined COPD [82].

●Alternatives to FEV₁/FVC – The forced expiratory volume in six seconds (FEV₆), obtained by stopping the expiratory effort after six seconds rather than at cessation of airflow, is an acceptable surrogate for the FVC [83-87]. The advantages of the FEV₁/FEV₆ include less frustration by the patient and technician trying to achieve an end-of-test plateau, less chance of syncope, shorter testing time, and better repeatability, without loss of sensitivity or specificity. If used, the LLN for FEV₁/FEV₆ from the Third National Health and Nutrition Examination Survey (NHANES III) is a reasonable threshold to diagnose airflow limitation. Global Lung Function Initiative (GLI) spirometry equations do not include FEV₆ reference values, so this method cannot be used with spirometry software that relies on these equations. (See "Office spirometry", section on 'Forced expiratory volume in six seconds' and "Office spirometry", section on 'Ratio of FEV1/FVC'.)

Additional testing — In the setting of chronic respiratory symptoms and appropriate risk factors, spirometry is the only testing required for the diagnosis of COPD. Additional testing is directed at ruling out alternative diagnoses.

●Laboratory studies – For patients with dyspnea, we obtain laboratory studies as part of a broad evaluation for potential etiologies. This often includes a complete blood count for assessment of anemia, an assessment of electrolytes and kidney function, a thyroid-stimulating hormone level, and a plasma BNP or N-terminal pro-BNP (NT-proBNP) concentration as a component of the evaluation of suspected heart failure (HF). (See "Approach to the patient with dyspnea", section on 'Initial testing in chronic dyspnea'.)

●Chest radiograph – For patients with suspected COPD, we typically obtain a chest radiograph to evaluate for alternative parenchymal processes and assess pulmonary comorbidities. Plain chest radiographs have a poor sensitivity for detecting COPD. As an example, only about half of patients with COPD of moderate severity are identified as having COPD by a plain chest radiograph (ie, sensitivity of 50 percent).

Radiographic features suggestive of COPD (usually seen in advanced disease) include:

•Rapidly tapering vascular shadows, increased radiolucency of the lung, a flat diaphragm, and a long, narrow heart shadow on a frontal radiograph (image 1).

•A flat diaphragmatic contour and an increased retrosternal airspace on a lateral radiograph (image 2). These findings are due to hyperinflation.

•Bullae, defined as radiolucent areas larger than one centimeter in diameter and surrounded by arcuate hairline shadows. They are due to locally severe disease and may or may not be accompanied by widespread emphysema (image 3).

•When advanced COPD leads to pulmonary hypertension and cor pulmonale, prominent hilar vascular shadows and encroachment of the heart shadow on the retrosternal space may be seen [88,89]. The cardiac enlargement may become evident only by comparison with previous chest radiographs. (See "Treatment and prognosis of pulmonary arterial hypertension in adults (group 1)".)

●Computed tomography, for alternative diagnoses or if spirometry is not available – There are settings where thoracic CT is routinely available and accessible, whereas spirometric testing can be challenging to obtain. CT has greater sensitivity and specificity than standard chest radiography for the detection of emphysema. This is particularly true with high-resolution computed tomography (HRCT; ie, collimation of 1 to 2 mm) [90-94]. Expiratory scans, particularly when used in conjunction with the inspiratory scans, can help to assess nonemphysematous air trapping as a surrogate measure for small airway abnormalities [95] (see "High resolution computed tomography of the lungs").

In the absence of other findings, CT-detected emphysema, air trapping, and airway remodelling involving a significant portion of the lungs is highly suggestive of COPD, and some have advocated for these findings as an alternative diagnostic pathway [52]. Because spirometry has a larger role in disease staging, is more cost-effective, and avoids unnecessary radiation exposure, we do not favor this approach unless spirometry cannot be obtained.

CT scanning may also be performed when symptoms or the physical examination suggest a potential complication of COPD (eg, pneumonia, pneumothorax, giant bullae), an alternate diagnosis (eg, thromboembolic disease) is suspected, or lung cancer screening is indicated [1]. (See "Evaluation and medical management of giant bullae", section on 'Evaluation' and "Clinical presentation, evaluation, and diagnosis of the nonpregnant adult with suspected acute pulmonary embolism" and "Screening for lung cancer", section on 'Low-dose chest CT'.)

Certain CT scan features can anatomically characterize the emphysema as centriacinar (centrilobular), panacinar, or paraseptal, although this is usually not necessary for clinical management [93,96]:

•Centriacinar emphysema occurs preferentially in the upper lobes and produces holes in the center of secondary pulmonary lobules. The walls of emphysematous spaces are usually imperceptible, but central vessels may be visible (image 4). In contrast, the walls of cysts in pulmonary Langerhans histiocytosis, another cystic lung disease of cigarette smokers, are thicker (image 5). (See 'Pathology' above.)

•Panacinar emphysema more commonly involves the lung bases and involves the entire secondary pulmonary lobule (image 6). Panacinar emphysema can cause a generalized paucity of vascular structures. Among patients with alpha-1 antitrypsin deficiency, panacinar emphysema is the more common pattern. (See "Clinical manifestations, diagnosis, and natural history of alpha-1 antitrypsin deficiency", section on 'Clinical manifestations'.)

•Paraseptal (distal acinar) emphysema produces small, subpleural collections of gas located in the periphery of the secondary pulmonary lobule (image 7). It is considered to be the precursor of bullae (image 8). (See 'Pathology' above.)

Newer CT scanners with higher resolution and new analytical methods can resolve airway dimensions, although the clinical significance of these measures is undefined [93,97-99]. Similarly, high-resolution scans can detect pruning of the distal vascular tree, which arises from destruction of alveoli and their associated capillary beds due to emphysema [34]. Quantitative parameters based on lung density, airway wall thickening, airway dilation, and vascular pruning have all been established to gauge severity of emphysema, airway disease, and pulmonary vascular pathology, respectively, but they have been used primarily as research tools and are not yet widely available.

DIAGNOSIS — The presence of symptoms compatible with COPD (eg, dyspnea at rest or on exertion, cough with or without sputum production, progressive limitation of activity) is suggestive of the diagnosis, especially if there is a history of exposure to triggers of COPD (eg, tobacco smoke, occupational dust, indoor biomass smoke), a family history of chronic lung disease, or presence of associated comorbidities (table 1). (Related Pathway(s): Chronic obstructive pulmonary disease: Initial diagnosis.)

The diagnosis of COPD is confirmed by the following [1,100]:

●Spirometry demonstrating airflow limitation (ie, a forced expiratory volume in one second/forced vital capacity [FEV₁/FVC] ratio less than 0.7 or below the lower limit of normal [LLN]) that is incompletely reversible after the administration of an inhaled bronchodilator (table 4A-B). (See 'Spirometry' above.)

●Absence of an alternative explanation for the symptoms and airflow limitation (table 5) [1]. The differential diagnosis of COPD is discussed below. (See 'Differential diagnosis' below and "Approach to the patient with dyspnea".)

DIFFERENTIAL DIAGNOSIS — Among patients who present in mid or later life with dyspnea, cough, and sputum production, the differential diagnosis is broad (eg, heart failure, COPD, interstitial lung disease, thromboembolic disease) (table 5). Typically, persistent airflow limitation on pulmonary function testing and absence of radiographic features of heart failure or interstitial lung disease direct the clinician to a narrower differential, which includes COPD, chronic obstructive asthma, bronchiectasis, tuberculosis, constrictive bronchiolitis, and diffuse panbronchiolitis [1]. Importantly, these conditions are not mutually exclusive and commonly occur together. For example, patients with asthma may develop COPD, and patients with COPD may have concurrent bronchiectasis.

●Chronic obstructive asthma – Older patients with a lifetime history of asthma may develop chronic airway remodeling including fixed airway obstruction. For patients without risk factors for COPD, chronic obstructive asthma is the presumed diagnosis in these cases. In patients with risk factors for COPD, however, a clear distinction between chronic obstructive asthma and COPD is not possible. As an example, a patient who has suffered from atopic asthma since childhood and smoked cigarettes for 15 years in their twenties and thirties could present in their fifties with a combination of asthma and COPD. Recognizing the coexistence of these diseases is essential in devising a treatment plan that reflects both underlying disease processes. (See 'Interrelationships among these conditions' above and "Asthma in adolescents and adults: Evaluation and diagnosis" and "Asthma and COPD overlap (ACO)".)

●Chronic bronchitis with normal spirometry – A small portion of cigarette smokers have a chronic productive cough for three months in each of two successive years but do not have airflow limitation on pulmonary function tests. They are not considered to have COPD, although they may develop COPD if they continue to smoke. (See 'Interrelationships among these conditions' above.)

●Central airway obstruction – Central airway obstruction can be caused by numerous benign and malignant processes and can mimic COPD with a slowly progressive dyspnea on exertion followed by dyspnea with minimal activity (table 7). Monophonic wheezing or stridor may be present. Symptoms are minimally improved by inhaled bronchodilator, if at all. A high index of suspicion is needed as conventional chest radiographs are rarely diagnostic. Though insensitive, flow-volume loops can show the characteristic changes of central airway obstruction, frequently before abnormalities in the spirometric volumes are noted (figure 1 and figure 2) [101]. A high-resolution computed tomography (HRCT) scan with three-dimensional reconstruction can be helpful. The gold standard for diagnosis is direct visualization. (See "Clinical presentation, diagnostic evaluation, and management of malignant central airway obstruction in adults", section on 'Diagnostic evaluation and initial management' and "Presentation and diagnostic evaluation of non-life-threatening and nonmalignant subglottic and tracheal stenosis in adults", section on 'Initial diagnostic testing'.)

●Bronchiectasis – Bronchiectasis, a condition of abnormal widening of the bronchi that is associated with chronic or recurrent infection, shares many clinical features with COPD, including inflamed and easily collapsible airways, obstruction to airflow, and exacerbations characterized by increased dyspnea and sputum production. Bronchiectasis is suspected on the basis of prominent symptoms of cough and daily mucopurulent sputum production. The diagnosis is usually established clinically based on the characteristic cough and sputum production and the presence of bronchial wall thickening and luminal dilatation on chest CT scans. (See "Clinical manifestations and diagnosis of bronchiectasis in adults".)

●Heart failure – Heart failure is a common cause of dyspnea among middle-aged and older patients and some patients experience chest tightness and wheezing with fluid overload due to heart failure. Occasionally, airflow limitation is noted, although a restrictive pattern is more common. Heart failure is usually differentiated by the presence of fine basilar crackles, radiographic evidence of an increased heart size, and pulmonary edema. The brain natriuretic peptide (BNP) is typically increased in heart failure but can also be increased during right heart strain from cor pulmonale. (See "Heart failure: Clinical manifestations and diagnosis in adults".)

●Tuberculosis – In an area endemic for tuberculosis, the overall prevalence of airflow obstruction was 31 percent among those with a past history of tuberculosis compared with 14 percent among those without [102,103]. This association was unchanged after adjustment for respiratory disease in childhood, smoking, and exposure to dust and smoke. Thus, tuberculosis is both a risk factor for COPD and a potential comorbidity [1]. (See "Pulmonary tuberculosis: Clinical manifestations and complications".)

●Constrictive bronchiolitis – Constrictive bronchiolitis, also known as bronchiolitis obliterans, is characterized by submucosal and peribronchiolar fibrosis that causes concentric narrowing of the bronchiolar lumen. Constrictive bronchiolitis is most commonly seen following inhalation injury, transplantation (eg, bone marrow, lung), or in the context of rheumatoid lung or inflammatory bowel disease (table 8). Symptoms include progressive onset of cough and dyspnea associated with hypoxemia at rest or with exercise. Crackles may be present. Pulmonary function tests show a progressive and irreversible airflow limitation. Findings on inspiratory CT scan include centrilobular bronchial wall thickening, bronchiolar dilation, tree-in-bud pattern, and a mosaic ground-glass attenuation pattern. (See "Overview of bronchiolar disorders in adults", section on 'Bronchiolitis obliterans'.)

●Diffuse panbronchiolitis – Diffuse panbronchiolitis is predominantly seen in male nonsmokers of East Asian descent. Almost all have chronic sinusitis. On pulmonary function testing, an obstructive defect is common, although a mixed obstructive-restrictive pattern may also be seen. Chest radiographs and HRCT scans show diffuse centrilobular nodular and linear opacities corresponding to thickened and dilated bronchiolar walls with intraluminal mucous plugs. (See "Diffuse panbronchiolitis", section on 'Diagnosis'.)

●Lymphangioleiomyomatosis – Lymphangioleiomyomatosis (LAM) is seen primarily in young females of childbearing age. Pulmonary function testing frequently reveals mild airflow obstruction, although a mixed obstructive-restrictive pattern may be seen. CT scans typically demonstrate small, thin-walled cysts that can at times be confused with emphysema. However, the airspaces in emphysema are not actually cysts but are caused by the destruction of alveolar walls and permanent enlargement of distal airspaces, so the "walls" are typically inapparent. (See 'Diagnosis' above and "Sporadic lymphangioleiomyomatosis: Epidemiology and pathogenesis" and "Diagnostic approach to the adult with cystic lung disease".)

POST-DIAGNOSTIC WORK-UP — Following a diagnosis of COPD, additional testing may be appropriate to assess disease severity and guide optimal initial therapeutic management.

Etiologic evaluation, including alpha-1 antitrypsin testing — If not performed prior to establishing the diagnosis, a new diagnosis of COPD should prompt a search for underlying etiologic factors. For many patients, the etiology is long-term cigarette smoking. However, it is important to review with the patient whether underlying asthma, workplace exposures, indoor use of biomass fuel, a prior history of tuberculosis, or familial predisposition is contributory because mitigation of ongoing exposures may reduce disease progression (table 2). (See 'Risk factors, including smoking and inhalational exposures' above and "Chronic obstructive pulmonary disease: Risk factors and risk reduction".)

It is appropriate to test all patients with COPD for alpha-1 antitrypsin (AAT) deficiency by obtaining an AAT serum level and AAT genotyping (algorithm 2) [1,104,105]. (See "Clinical manifestations, diagnosis, and natural history of alpha-1 antitrypsin deficiency", section on 'Evaluation and diagnosis'.)

Exercise capacity — Objectively measured exercise impairment is a strong signal of overall health status and a predictor of prognosis in COPD [106,107]. For patients with COPD, we perform a formal six-minute walk test with ambulatory oximetry measurement. This allows for assessment of exercise capacity as well as a determination of gas exchange during exercise. Patients with exertional hypoxemia should have further assessment of their gas exchange. (See 'Assessing gas exchange, in select patients' below.)

Timed walking tests can assess pulmonary disability and may uncover previously unrecognized severe disease in patients with reduced dyspnea perception or sedentarism. Exercise testing is also standard part of preprogram evaluation for pulmonary rehabilitation, which is recommended for COPD patients with dyspnea or a history of exacerbations. (See "Evaluation of pulmonary disability", section on 'Exercise tests' and "Pulmonary rehabilitation", section on 'Preprogram evaluation'.)

Lung volumes, for those with impaired vital capacity — When a reduced forced vital capacity (FVC) is present on postbronchodilator spirometry, we perform lung volume measurement by body plethysmography to determine whether the reduction in FVC is due to air trapping, hyperinflation, or a concomitant restrictive ventilatory defect. Body plethysmography is strongly preferred for lung volume measurement when available because gas dilution methods may be insensitive for the detection of air trapping. Decreased inspiratory capacity (IC) and vital capacity, accompanied by an increased total lung capacity (TLC), functional residual capacity (FRC), and residual volume (RV), are indicative of hyperinflation. An increased FRC or RV with a normal TLC is indicative of air trapping without hyperinflation. Restrictive deficits will present with a reduced TLC, and restrictive interstitial lung diseases will demonstrate reductions in TLC, FRC, and RV. (See "Overview of pulmonary function testing in adults", section on 'Lung volumes' and "Dynamic hyperinflation in patients with COPD".)

Assessing gas exchange, in select patients — We perform additional assessment of gas exchange in patients with COPD with moderate to severe airflow limitation (forced expiratory volume in one second [FEV₁] ≤50 percent predicted or z-score ≤-2.5), marginal resting oxygen saturation [O₂Sat] (O₂Sat ≤92 percent), exertional hypoxemia (O₂Sat <90 percent), or severe dyspnea (modified Medical Research Council [mMRC] score ≥2) (calculator 1).

●Diffusing capacity for carbon monoxide (DLCO) – Although DLCO decreases in proportion to the severity of emphysema in most patients with COPD, it cannot be used to detect mild emphysema because it is neither a sensitive nor a specific test. However, reductions in DLCO are associated with increased symptoms, worsened health status, and increased risk of death independently of airflow obstruction and other clinical findings [108-110]. DLCO reductions out of proportion to airflow limitation may suggest concomitant restrictive lung disease or pulmonary hypertension, which require further work-up. (See "Clinical features and diagnosis of pulmonary hypertension of unclear etiology in adults".)

●Arterial blood gas – A resting arterial blood gas demonstrating arterial oxygen tension (PaO₂) ≤55 mmHg (7.33 kPa) is an indication for continuous supplemental oxygen. Similarly, the presence of chronic respiratory acidosis (figure 3 and figure 4) should lead to evaluation for sleep-disordered breathing and possible nocturnal noninvasive ventilation. (See "Long-term supplemental oxygen therapy" and "Nocturnal ventilatory support in COPD".)

●CT imaging – While chest CT imaging is not recommended for all patients, we agree with the global initiative for obstructive lung disease recommendations, which suggest CT imaging in the following circumstances: patients with persistent exacerbations; symptoms out of proportion to disease severity on lung function testing; FEV₁ less than 45 percent predicted with significant hyperinflation (as consideration for endobronchial valve placement); those meeting criteria for lung volume reduction surgery; and patients meeting criteria for lung cancer screening [1].

ASSESSMENT OF SEVERITY AND STAGING — Several different strategies have been devised to categorize patients for the purposes of disease management and prognosis. While historical approaches generally weighed spirometric values more strongly, it has been increasingly recognized that other aspects of disease, such as the severity of symptoms, risk of exacerbations, and the presence of comorbidities, are important to the patient's experience and to disease prognosis [1,111].

GOLD classification systems — While the Global Initiative for Chronic Obstructive Lung Disease (GOLD) strategy recommends COPD diagnosis using symptoms accompanied by a forced expiratory volume in one second (FEV₁)/ forced vital capacity (FVC) ratio <0.7, the severity of obstruction is determined by the FEV₁ percent predicted. The GOLD system uses four grades:

●GOLD 1 (mild disease): FEV₁ ≥80 percent predicted

●GOLD 2 (moderate disease): FEV₁ between 50 and 80 percent predicted

●GOLD 3 (severe disease): FEV₁ between 30 and 50 percent predicted

●GOLD 4 (very severe disease): FEV₁ <30 percent predicted

This spirometric severity grading system is important due to its simplicity and subsequent use in many clinical trials and observational studies; however, its prognostic capacity for mortality is modest [112].

Other groups have suggested potential spirometry-derived alternatives to the GOLD Grade system. For example, the STaging of Airflow obstruction by Ratio (STAR) severity classification scheme was derived using approximately the 25^th, 50^th, and 75^th percentile of the FEV₁/FVC ratios from the COPDGene cohort study and validated using COPDGene and a second independent cohort [113]. Like GOLD, this classification divides patients with COPD into 4 stages: STAR stage 1 is defined by an FEV₁/FVC ratio between 0.6 and 0.7; STAR stage 2 by an FEV₁/FVC ratio between 0.5 and 0.6; STAR stage 3 by an FEV₁/FVC ratio between 0.4 and 0.5; and STAR stage 4 by an FEV₁/FVC ratio <0.4.

The GOLD and STAR systems provided similar discrimination for mortality and successfully separated patients in the studied observational cohorts by dyspnea, respiratory quality of life, and imaging assessments of disease [113]. A potential advantage of the STAR system is that it does not rely on predicted lung size based on age, height, or race/ethnicity. It does, however, depend on obtaining good-quality spirometry (eg, expiratory plateau in the last second of expiration or expiratory time ≥15 seconds) [114]. STAR requires further validation in population-based cohorts before it can be widely adopted.

While GOLD grade relates to spirometric severity of disease, GOLD recommends a different system, the ABE assessment tool, for use in determining initial therapy. The GOLD ABE assessment tool uses an individual’s symptoms (ie, modified Medical Research Council [mMRC] dyspnea scale (calculator 1) or COPD Assessment Test (calculator 2)) and exacerbation history to guide pharmacotherapy (algorithm 3) [1]. The multidimensional GOLD "ABE" evaluation is discussed in more detail separately in the context of initial management of COPD. (See "Stable COPD: Initial pharmacologic management".) (Related Pathway(s): Chronic obstructive pulmonary disease: Severity assessment and selection of initial therapy in adults.)

We agree with the GOLD strategy to monitor postbronchodilator spirometry yearly to track decline in FEV₁, which may identify patients whose disease is progressing more quickly than usual. Follow-up spirometric assessment may also be helpful in therapeutic decision making when considering multiple potential causes of worsening dyspnea. Finally, spirometric values remain an essential component of decision making for lung volume reduction and lung transplantation. (See "Management of refractory chronic obstructive pulmonary disease", section on 'Lung Volume Reduction, in select patients with dyspnea' and "Management of refractory chronic obstructive pulmonary disease", section on 'Lung transplantation'.)

BODE index — The BODE index is another system for assessment of COPD severity and prognosis. It is calculated based on weight (body mass index [BMI]), airflow limitation (FEV₁), dyspnea (mMRC dyspnea score) (calculator 1), and exercise capacity (six-minute walk distance) (calculator 3), and it has been used to assess an individual’s risk of death. This index provides better prognostic information than the FEV₁ alone and can be used to assess therapeutic response to medications, pulmonary rehabilitation therapy, and other interventions [106,107,113,115]. (See "Chronic obstructive pulmonary disease: Prognostic factors and comorbid conditions", section on 'BODE index'.)

COPD Foundation system — The COPD Foundation has introduced a system that includes seven severity domains, each of which has therapeutic implications (figure 5) [56,100]. These domains are based upon assessment of spirometry, regular symptoms, number of exacerbations in the past year, oxygenation, emphysema on CT scan or air trapping on lung volumes, presence of chronic bronchitis, and comorbidities. Within the spirometry domain, the COPD Foundation uses five grades:

●SG 0: Normal spirometry

●SG 1: Mild, postbronchodilator FEV₁/forced vital capacity (FVC) ratio <0.7, FEV₁ ≥60 percent predicted

●SG 2: Moderate, postbronchodilator FEV₁/FVC ratio <0.7, FEV₁ between 30 and 60 percent predicted

●SG 3: Severe, postbronchodilator FEV₁/FVC ratio <0.7, FEV₁ <30 percent predicted

●SG U: Undefined, postbronchodilator FEV₁/FVC ratio >0.7, FEV₁ <80 percent predicted

An advantage of this staging system is that it simplifies the interpretation of spirometry; any spirometric finding results in a classification, which is not the case in the GOLD system.

While FEV₁ is used to gauge severity, the FEV₁/FVC ratio is not used for this purpose because measurement of FVC becomes less reliable as the disease progresses (the long exhalations are difficult for the patients), thus making the ratio less accurate unless high-quality spirometry is ensured (algorithm 1). (See "Chronic obstructive pulmonary disease: Prognostic factors and comorbid conditions", section on 'Forced expiratory volume in one second' and "Office spirometry", section on 'Interpretation'.)

SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Chronic obstructive pulmonary disease".)

INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, “The Basics” and “Beyond the Basics.” The Basics patient education pieces are written in plain language, at the 5^th to 6^th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10^th to 12^th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.

Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on “patient info” and the keyword(s) of interest.)

●Basics topics (see "Patient education: Chronic obstructive pulmonary disease (COPD) (The Basics)" and "Patient education: Chronic bronchitis (The Basics)" and "Patient education: Medicines for COPD (The Basics)")

●Beyond the Basics topics (see "Patient education: Chronic obstructive pulmonary disease (COPD) (Beyond the Basics)")

SUMMARY AND RECOMMENDATIONS

●Definitions – The Global Initiative for Chronic Obstructive Lung Disease (GOLD) defines COPD as follows: "COPD is a heterogeneous lung condition characterized by chronic respiratory symptoms due to abnormalities of the airway and/or alveoli that cause persistent, often progressive, airflow obstruction." (See 'Definitions' above.)

Substantial overlap exists between COPD and the other disorders that may cause airflow limitation (eg, emphysema, chronic bronchitis, asthma, bronchiectasis, bronchiolitis). (See 'Interrelationships among these conditions' above.)

●Clinical features – Common presentations of COPD include patients with few complaints but an extremely sedentary lifestyle; patients with chronic, daily respiratory symptoms (eg, dyspnea on exertion, cough); and patients with recurrent acute exacerbations (eg, wheezing, cough, dyspnea, fatigue). Patients should be asked about current smoking and the number of pack-years smoked (packs of cigarettes per day multiplied by the number of years); other inhalational exposures; tuberculosis, HIV, and childhood pulmonary infections; a history of asthma; and a family history of lung diseases. The physical examination of the chest varies with the severity of the COPD but is often normal in mild disease (table 4A-B). (See 'Clinical Presentation' above.)

●Diagnostic evaluation – The diagnosis of COPD should be considered and spirometry performed pre- and postbronchodilator administration in all patients who report any combination of dyspnea, chronic cough, or chronic sputum production, especially if there is a history of exposure to triggers of COPD (eg, tobacco smoke, occupational dust, indoor biomass smoke), a family history of chronic lung disease, or presence of associated comorbidities (table 1). For individuals with risk factors, use of the CAPTURE (Chronic obstructive pulmonary disease Assessment in Primary care To identify Undiagnosed Respiratory disease and Exacerbation risk) questionnaire and peak flow measurement to assess unreported symptoms and potential air flow limitation may identify additional symptomatic patients appropriate for further evaluation. (Related Pathway(s): Chronic obstructive pulmonary disease: Initial diagnosis.)

•Spirometry pre- and postbronchodilator – COPD is confirmed when a patient with compatible symptoms is found to have irreversible airflow limitation (ie, a postbronchodilator forced expiratory volume in one second [FEV₁]/forced vital capacity [FVC] ratio less than 0.7 [or below the lower limit of normal (LLN)]) and no alternative explanation for the symptoms and airflow obstruction. (See 'Spirometry' above and 'Diagnosis' above.)

•Additional testing – In the evaluation of patients with COPD, laboratory studies and chest radiography are typically performed to exclude alternative diagnoses, evaluate for comorbidities, or assess a change in symptoms that suggests a complication of COPD. Chest CT is performed to evaluate abnormalities seen on the conventional chest radiograph, to exclude certain complications of COPD (eg, thromboembolic disease, lung cancer), or when a patient is being considered for lung volume reduction surgery, endobronchial valves, or lung transplantation. (See 'Additional testing' above.)

●Differential diagnosis – Among patients who present in mid- or later-life with dyspnea, cough, and sputum production, the differential diagnosis is broad (eg, heart failure, COPD, interstitial lung disease, thromboembolic disease) (table 5). (See 'Differential diagnosis' above.)

●Post-diagnostic work-up – Following a diagnosis of COPD, additional testing may be appropriate to assess disease severity and guide optimal initial therapeutic management.

•Etiologic evaluation, including alpha-1 antitrypsin testing – If not performed prior to establishing the diagnosis, a new diagnosis of COPD should prompt a search for underlying etiologic factors (table 2). It is appropriate to test all patients with COPD for alpha-1 antitrypsin (AAT) deficiency by obtaining an AAT serum level and AAT genotyping (algorithm 2).

•Exercise capacity – For patients with COPD, we perform a formal six-minute walk test with ambulatory oximetry measurement. This allows for assessment of exercise capacity as well as a determination of gas exchange during exercise.

•Other studies – Assessment of lung volumes and gas exchange are appropriate for patients with evidence of more severe disease. (See 'Lung volumes, for those with impaired vital capacity' above and 'Assessing gas exchange, in select patients' above.)

●Assessment of severity and staging

•The original GOLD staging system was based solely on postbronchodilator FEV₁. Although well-recognized and commonly used, it has been criticized for underestimating the importance of the severity of symptoms, risk of exacerbations, and presence of comorbidities in predicting outcome. (See 'Assessment of severity and staging' above.)

•The revised GOLD "ABE" strategy uses a combination of an individual's symptoms and history of exacerbations and hospitalizations due to exacerbations to stratify symptoms and exacerbation risk and guide therapy (algorithm 3). (See 'GOLD classification systems' above.)

•Other multidimensional staging systems include the BODE index (calculator 3) and the COPD Foundation system (figure 5). (See 'BODE index' above and 'COPD Foundation system' above.)

ACKNOWLEDGMENT — The editorial staff at UpToDate acknowledge Stephen Rennard, MD, who contributed to earlier versions of this topic review.