ANA: antinuclear antibody test; BAL: bronchoalveolar lavage; COP: cryptogenic organizing pneumonia; cryo-TBB: transbronchial cryobiopsy; DIP: desquamative interstitial pneumonitis; EBUS: endobronchial ultrasound; HP: hypersensitivity pneumonitis; HRCT: high-resolution computed tomography; IIP: idiopathic interstitial pneumonia; ILD: interstitial lung disease; IPF: idiopathic pulmonary fibrosis; NSIP: nonspecific interstitial pneumonia; PLCH: pulmonary Langerhans cell histiocytosis; TBB: transbronchial lung biopsy; UIP: usual interstitial pneumonia.
* ILD protocols for HRCT of the chest include volumetric inspiration, expiration, and prone imaging to assess for air-trapping, small airways disease, and dependent atelectasis.
¶ Additional testing for connective tissue disease and myositis may be performed either during the initial work-up, especially for those with demographic or known imaging features atypical for IPF, or as indicated by clinical or radiologic findings after the initial work-up. This testing includes creatine kinase, aldolase, myositis/antisynthetase antibody panel, and an extractable nuclear antigen antibody panel (including Sjögren-associated antibodies [anti-Ro60, anti-Ro52, and anti-La] and scleroderma-associated antibodies [anti-SCL-70 and anti-centromere]).
Δ Common environmental or iatrogenic etiologies include: drug toxicities (bleomycin, immune checkpoint inhibitors, nitrofurantoin, nitrosoureas), radiation therapy to the thorax, inhaled inorganic dusts (eg, silica, asbestos, beryllium, coal), and inhaled organics (hay and grains, humidifiers/indoor pool, feathers, molds). Any of these exposures in the setting of appropriate history and imaging findings may explain the presence of ILD.
◊ Features of definite and probable UIP include: reticular opacities in a basal and peripheral distribution, traction bronchiectasis, honeycombing (clustered airspaces 3 to 10 mm diameter) in a subpleural location, and lack of extensive ground-glass opacities.
§ IIPs are non-granulomatous diffuse parenchymal lung disease of unknown etiology, including: IPF, NSIP, COP, acute interstitial pneumonia, respiratory bronchiolitis ILD, and DIP.
¥ For patients who have a nondiagnostic cryo-TBB, subsequent surgical lung biopsy may be appropriate to obtain a diagnosis.