Version July 2025
INTRODUCTION —
Autism spectrum disorder (ASD) is a biologically based neurodevelopmental disorder that presents in early childhood and requires ongoing evaluation and intervention. Surveillance and screening for ASD in primary care is important to the early diagnosis and management of ASD.
The terminology and diagnostic criteria for ASD vary geographically and are based on the DSM-5-TR (United States) and the ICD-11 (World Health Organization) [1-3]. However, the slight inconsistencies between the DSM-5-TR and ICD-11 terminology do not affect the rationale or process for surveillance and screening for ASD.
Adult advocates with ASD view autism as a personal characteristic that is a life-long part of an individual's identity and prefer identity-first (eg, "autistic individual") rather than person-first (eg, "individual with autism") language. They also prefer the term "autism" to "autism spectrum disorder." We respect these viewpoints. In this topic, we use "autism spectrum disorder (ASD)" and person-first language in agreement with the diagnostic terminology and the common style used in medical journals. However, clinicians should be sensitive to changes in terminology and inquire about individual preferences in discussions with their patients.
The rationale and process for ASD surveillance and screening in primary care will be reviewed here. General developmental screening, ASD-specific screening tools, and the pathogenesis, clinical features, diagnosis, and management of ASD are discussed separately.
●(See "Developmental-behavioral surveillance and screening in primary care".)
●(See "Autism spectrum disorder in children and adolescents: Screening tools".)
●(See "Autism spectrum disorder in children and adolescents: Clinical features".)
●(See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis".)
●(See "Autism spectrum disorder in children and adolescents: Overview of management and prognosis".)
TERMINOLOGY
●Surveillance – In this topic, surveillance refers to a process for identifying potential risk factors for ASD. This is a flexible, continuous process whereby knowledgeable professionals collect information from multiple sources (eg, observation of children during health care visits, asking specific questions to elicit parent/caregiver concerns) to identify and address developmental issues [4,5]. General principles of surveillance are described in greater detail separately. (See "Developmental-behavioral surveillance and screening in primary care", section on 'Approach to surveillance'.)
●Screening – In this topic, screening refers to a brief, formal, standardized evaluation for early identification of patients with developmental and behavioral differences that are suggestive of ASD. A screening instrument enables detection of conditions or concerns that may not be readily apparent without screening and identification of children who require additional investigation by clinicians with special expertise in ASD [6]. Effective screening requires considering results from standardized screening tests in conjunction with clinical judgment. (See "Developmental-behavioral surveillance and screening in primary care", section on 'Approach to screening'.)
BENEFITS OF EARLY IDENTIFICATION —
Surveillance and screening aid in the early identification of ASD, which is an important step in optimizing outcomes. Early identification facilitates [6-14]:
●Initiation of early interventions (see "Autism spectrum disorder in children and adolescents: Behavioral and educational interventions")
●Earlier education planning (see "Autism spectrum disorder in children and adolescents: Behavioral and educational interventions", section on 'Educational programming')
●Parent/caregiver and family support (see "Autism spectrum disorder in children and adolescents: Overview of management and prognosis", section on 'Family support')
●Delivery of appropriate medical care and treatment of associated conditions (see "Autism spectrum disorder in children and adolescents: Overview of management and prognosis", section on 'Role of the primary care provider')
●Genetic counseling (particularly if the child has a condition associated with ASD, such as tuberous sclerosis complex) (see "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis", section on 'Genetic testing')
CHALLENGES OF EARLY IDENTIFICATION —
Surveillance and screening for the early identification of ASD are challenging for a number of reasons, including the time constraints of a typical office visit, the vague nature of social developmental milestones, and the variability of the signs and symptoms of ASD in individual children. In addition, ASD may be "masked" or exacerbated by coexisting problems (eg, anxiety, hyperactivity, mood disorder, developmental delay), which can affect the timing or accuracy of diagnosis. (See "Autism spectrum disorder in children and adolescents: Clinical features".)
Clinical features and other factors that may delay diagnosis include [15-18]:
●Less severe symptoms
●Coexisting behavioral problems (eg, anxiety, hyperactivity, mood disorder)
●Hearing impairment
●Oversensitivity to pain
●Attribution of regression of skills to "stressors" (eg, birth of a sibling)
●Female sex
●Lack of continuity of care
●Language barriers
●Being in an underrepresented racial/ethnic group
●Living in a rural area
●Lower socioeconomic status
Surveys of families of children with ASD indicate that delays between the onset of parent/caregiver concerns and comprehensive evaluation and between comprehensive evaluation and diagnosis of ASD are common [19-21]. In a multicenter surveillance study of children with ASD, 85 percent of parents expressed concern about general developmental delay at ≤36 months of age, yet only 61 percent of the children had undergone a comprehensive evaluation at ≤48 months of age, and the median age of diagnosis was 52 months (range 46 to 67 months depending upon the severity of symptoms) [15]. The surveillance methodology for this study did not capture delays in diagnosis for patients whose parents did not express concerns. In subsequent multicenter surveillance studies of children with ASD, the age at diagnosis improved, with 72 percent of four-year-old children having an initial evaluation at age ≤36 months; the median age of earliest diagnosis in eight-year-old children was 59 months [22,23].
Details regarding other challenges of surveillance and screening for developmental-behavioral conditions are discussed separately. (See "Developmental-behavioral surveillance and screening in primary care", section on 'Perceived harms and burdens of surveillance and screening'.)
SURVEILLANCE AND EARLY INDICATORS OF ASD
Routine developmental-behavioral assessment — Routine developmental-behavioral surveillance and screening includes ASD surveillance and consists of the following:
●Eliciting parent/caregiver concerns
●Maintaining a developmental history
●Observing the child's behavior
●Observing caregiver-child interactions
●Identifying risk and protective factors
●Periodic developmental screening
Routine developmental surveillance should occur at every well-child visit and includes screening for communication and social skills. Regular administration of developmental screening tests is recommended at the 9-, 18-, and 24- or 30-month visits, and when developmental concerns are raised [6,24,25]. Clinical features of ASD that may be identified during routine surveillance and lead to earlier evaluation and diagnosis include language delay, poor response to language and/or absent or reduced use of gestures such as pointing, and atypical behaviors such as hand flapping and toe walking [16,26].
Routine developmental and behavioral surveillance and screening in primary care is discussed in more detail separately. (See "Developmental-behavioral surveillance and screening in primary care".)
Eliciting and responding to caregiver concerns — It is important for the primary care clinician to listen carefully to the child's parents/caregivers and take their concerns seriously [27]. Asking targeted questions appropriate to the child's age may help to elicit concerns about ASD (table 1) [28,29].
If the concerns are suggestive of ASD, the primary care clinician can engage the child in simple interactions or an open-ended conversation to evaluate for atypical communication and social behaviors. For example, in younger children, the clinician can call the child's name to see if they turn or observe for communicative gestures. In older children, the clinician can ask the child about friendships, what they like to do during play dates or play time, etc. Both the content and style of the child's responses may reveal atypical communication and social behaviors. (See 'Early indicators of ASD' below.)
Assessments using standardized measures have shown that parents'/caregivers' concerns correlate with the early detection of developmental and behavioral problems [24,30-32]. Observing the child during the office visit is helpful in gathering information but is not sufficient because younger children are often upset or dysregulated during the visit, which makes it more difficult to assess their true developmental capacity or behaviors. In contrast, children with less severe ASD symptoms can often mask their symptoms because they have learned to manage the social demands of a routine pediatric office visit successfully, especially if they have normal intelligence and/or have been instructed about how to behave in the clinician's office.
Early indicators of ASD — Symptoms of ASD usually are present by 18 to 24 months of age and are of concern to parents/caregivers but may not be fully apparent until three years of age [19,20,33-36]. Prospective studies of children at risk for ASD and retrospective studies using home movies to examine the early development of children with ASD have identified findings that begin to emerge after approximately six months of age [37-42]. Other studies have identified findings before six months [43].
Early signs and symptoms of ASD by age include (table 2):
●<6 months – Decreased visual fixation (as measured by eye-tracking technology) [43]. However, this difference may not be apparent to the naked eye or may be physiologic at this age, so parents/caregivers of young infants should not be concerned if the infant does not always meet their eyes [44].
●6 to 12 months – A tendency to fixate on particular objects in the environment and declining frequency of response to name, gaze to faces, shared smiles, and vocalizations [38,39,41].
●12 to 24 months – Reduced frequency of sharing experiences, interests, or attention with others (eg, problems with eye contact, orienting to name, pretend play, imitation); repetitive behaviors; delayed expressive and receptive language; difficulty with nonverbal (eg, gestural) communication, and frequent tantrums or intolerance to change [38,41,42,45-55].
APPROACH TO ASD SCREENING
Evaluation of symptomatic children — All children with clinical findings suggestive of ASD identified on surveillance should undergo a comprehensive evaluation for ASD. This approach is generally consistent with recommendations from expert groups [6,25,27,56-59]. ASD-specific screening tools can be used as part of this assessment. The comprehensive evaluation and screening tools are described in detail separately. (See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis", section on 'Role of the primary care clinician' and "Autism spectrum disorder in children and adolescents: Screening tools".)
Children with clinical findings suggestive of ASD include:
●Children (regardless of age) who demonstrate, or whose parents/caregivers raise concerns for, signs of ASD such as impaired social communication and interaction (eg, reduced or absent joint attention, including decreased eye contact or response to name), atypical or repetitive behaviors (eg, hand flapping and toe walking), or rigid behavior that interferes with function (table 2 and table 3 and table 4)
●Children with delayed language and social communication milestones identified by routine developmental screening tests or parent/caregiver report (table 2 and table 5)
●Children with regression in social or language skills that are not better explained by other causes
The clinical features of ASD are discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Clinical features".)
Universal screening for asymptomatic children — For children without clinical findings of ASD, including those who may have risk factors for ASD (eg, a sibling diagnosed with ASD, a genetic condition associated with ASD), we suggest ASD-specific screening at 18 and 24 months of age. Population-based screening for ASD is endorsed by some [6,25,56,57], but not all, expert groups [58-60]. However, even when universal screening for ASD is not recommended by experts, routine developmental and behavioral screening as part of surveillance for ASD continue to be recommended. (See 'Surveillance and early indicators of ASD' above and 'Society guideline links' below.)
We suggest universal ASD-specific screening for the following reasons [6,9,56,58,61-77]:
●ASD prevalence – ASD is common, with a prevalence of approximately 1 in 40 to 1 in 500 children. (See "Autism spectrum disorder (ASD) in children and adolescents: Terminology, epidemiology, and pathogenesis", section on 'Prevalence'.)
●Early intervention is available and beneficial – Early screening for ASD can prompt referral for diagnostic evaluation, which in turn leads to earlier identification and intervention. Early intervention is associated with improved outcomes. (See "Autism spectrum disorder in children and adolescents: Overview of management and prognosis", section on 'Early intervention'.)
Behavioral and educational interventions are available for children who are diagnosed with ASD [6]. In the United States, there is a mandate to provide publicly funded special education and related services through the Education of All Handicapped Children Act (PL 94-142 and PL 99-457), and children who fail ASD screening can be referred for infant-toddler assessment through Part C of the Individuals with Disabilities Education Act. These interventions are discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Behavioral and educational interventions" and "Definitions of specific learning disorder and laws pertaining to learning disorders in the United States".)
●Benefits of screening outweigh harms – The potential benefits of early detection outweigh the challenges and potential harms of screening in asymptomatic children [65,68-74]. Harms include time, effort, and anxiety associated with further testing and prolonged delays in receiving specialist evaluation and supportive services; time and cost of behavioral treatments; potential for "false positive" screens; and inability of the clinician to adequately discuss the results of the screening.
●Potential for delayed diagnosis without formal screening – Although the diagnosis of ASD can be reliably made in children as young as 18 months of age [6,56], the median age of diagnosis in the United States is >4 years [23]. Early identification is complicated by the heterogeneity of presentation and the difficulty of differentiating symptoms of ASD from those of other developmental disorders. The presentation of atypical behaviors characteristic of ASD is particularly variable in young children and may be missed by clinicians and parents/caregivers unless routine screening is performed. Brief observation of children's behaviors alone is not sufficiently sensitive, even when performed by individuals with expertise in ASD while observing structured evaluation for ASD, because young children with ASD may demonstrate typical behavior more often than atypical behavior [67]. In addition, administration of formal screening tools during routine primary care visits may diminish the risk for delayed diagnosis and treatment in children who face disparities due to their socioeconomic status or ethnicity [78,79]. Other factors may also lead to a delay in diagnosis. (See 'Challenges of early identification' above.)
●Screening tools are effective – Available screening tools have appropriate sensitivity and specificity to identify children with ASD from the general population before three years of age [68-72,74]. Moreover, children with "false positive" screens for ASD frequently have other developmental disorders that are correctly diagnosed during the evaluation for ASD and can also benefit from early intervention. In large studies in community primary care settings, approximately 50 percent of young children who had a positive ASD screen were diagnosed with ASD and 98 percent had a developmental concern that warranted early intervention [68,75]. The sensitivity and specificity of screening tools is discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Screening tools", section on 'Tools for children <3 years'.)
●Diagnostic stability of ASD –The diagnosis of ASD is confirmed upon reassessment in the majority of cases (ie diagnostic stability), indicating that longitudinal screening and diagnostic evaluation for ASD can be effective [77,80]. The diagnostic stability of ASD is discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis", section on 'Diagnostic stability'.)
ASD-specific screening tools — We use ASD-specific screening tools (table 6) for children in whom ASD screening is indicated. ASD-specific screening tools systematically incorporate items that address the core symptoms of ASD and assess different domains of development than general developmental screening tools; the two tools are complementary [81]. However, early developmental screening tools that focus on communication skills may be helpful in the early identification of ASD [82].
ASD-specific screening tools are discussed in detail separately. (See "Autism spectrum disorder in children and adolescents: Screening tools".)
MANAGEMENT OF CHILDREN WHO SCREEN POSITIVE
Referrals and evaluation
●Early developmental and behavioral services – As with all children with developmental and behavioral impairments, children who screen positive for ASD should be referred for developmental and behavioral services without delay, even before confirmation of the diagnosis [6,33,57]. The earlier a child receives appropriate intervention, the better the long-term outcome [6,83]. In the United States, these services are provided by Early Intervention if the child is younger than three years of age and by the public school system if the child is older than three years. Evidence regarding the benefits of early intervention and special education services for developmental and behavioral impairments are discussed in more detail separately. (See "Developmental-behavioral surveillance and screening in primary care", section on 'Benefits of surveillance and screening' and "Developmental-behavioral surveillance and screening in primary care", section on 'Early intervention or special education services'.)
Referral for early intervention services and educational programs for ASD are discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis", section on 'Role of the primary care clinician' and "Autism spectrum disorder in children and adolescents: Behavioral and educational interventions", section on 'Attributes of successful educational programs'.)
●Comprehensive evaluation and monitoring – Children who screen positive for ASD should receive a comprehensive evaluation for ASD, preferably by a clinician or team that has expertise in the diagnosis and management of ASD [33]. The goals of this evaluation are to determine whether the child meets diagnostic criteria for ASD and to differentiate ASD from other developmental or behavioral conditions. The components of a comprehensive evaluation and management of ASD are discussed in more detail separately. (See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis" and "Autism spectrum disorder in children and adolescents: Overview of management and prognosis".)
Caregiver education and family support — Parent/caregiver education and family support is needed before, during, and after the evaluation process [6,84,85]. If the primary care clinician is reasonably confident that the child has ASD, it is helpful to provide educational materials for the parents/caregivers to review prior to the comprehensive evaluation. Even if the primary care clinician is not certain of the diagnosis or the child is not ultimately diagnosed with ASD, it is helpful to provide the family with education about the implications of a positive screen and interventions or supportive services that may be helpful in addressing the symptom(s) identified by the screening test [6]. This includes information about recommended therapies, appropriate schools or therapy centers, and other available resources such as government agencies for individuals with disabilities, caregiver/sibling support groups, and other community-based support systems. (See 'Resources' below.)
Families will also need ongoing guidance regarding unconventional and/or unproven alternative therapies and the importance of immunizations [6,76,84]. Parents/caregivers should be cautioned about misinformation and should be directed to reliable resources. Children with ASD and their siblings have higher rates of underimmunization compared with the general population [84]. Alternative therapies for ASD and vaccine hesitancy are discussed in more detail elsewhere. (See "Autism spectrum disorder in children and adolescents: Complementary and integrative medicine therapies", section on 'Counseling caregivers' and "Standard childhood vaccines: Caregiver hesitancy or refusal".)
MANAGEMENT OF CHILDREN WHO SCREEN NEGATIVE
Children with associated findings of ASD — Children who screen negative for ASD at 18 or 24 months but who have clinical findings of ASD should undergo a comprehensive evaluation for ASD regardless of the results of the ASD screen. Clinicians should interpret the results of ASD-specific screening tools in conjunction with clinical judgment and findings from other developmental and behavioral surveillance and screening. Children with atypical development should be referred for a comprehensive evaluation. (See "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis" and "Developmental-behavioral surveillance and screening in primary care", section on 'Positive screen'.)
Children ultimately diagnosed with ASD may have an initial negative screen at age 18 or 24 months [86-89]. In a prospective cohort of 68,197 children who screened negative on the Modified Checklist for Autism in Toddlers (M-CHAT) at age 18 months, 228 (0.3 percent) were subsequently diagnosed with ASD (ie, "false negatives") [86]. Although these children screened negative on the M-CHAT, they demonstrated atypical features and delays in social, communication, and motor skills on other developmental and behavioral screening tests (eg, selected items from the Ages and Stages Questionnaire and the Emotionality Activity Sociability Temperament Survey). The M-CHAT screen used in this study was subsequently revised to the M-CHAT, Revised with Follow-Up (M-CHAT-R/F). Whether the M-CHAT-R/F has a lower false-negative rate than the M-CHAT is uncertain. (See "Autism spectrum disorder in children and adolescents: Screening tools", section on 'Modified Checklist for Autism in Toddlers, Revised with Follow-Up'.)
Children without associated findings of ASD — Children who screen negative for ASD at 18 or 24 months of age and who do not have findings of ASD should continue to undergo routine developmental and behavioral surveillance and screening [25]. (See "Developmental-behavioral surveillance and screening in primary care".)
RESOURCES —
Families of children with ASD benefit from referral to community resources such as parent/caregiver groups, advocacy programs, and respite and recreational services. In the United States, many states provide additional services to families of children with ASD through the Department of Developmental Services (formerly Department of Mental Retardation) regardless of the child's cognitive functioning. Depending on income level, families may also qualify for Supplemental Security Income benefits. (See "Children and youth with special health care needs", section on 'Psychosocial and economic consequences'.)
Online resources for clinicians and families of individuals with ASD are provided in the table (table 7).
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: Developmental screening" and "Society guideline links: Autism spectrum disorder".)
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 5th to 6th 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 10th to 12th 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 email these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient education" and the keyword[s] of interest.)
●Basic topic (see "Patient education: Autism spectrum disorder (The Basics)")
●Beyond the Basics topic (see "Patient education: Autism spectrum disorder (Beyond the Basics)")
SUMMARY AND RECOMMENDATIONS
●Terminology – Surveillance refers to a process for identifying potential risk factors for ASD. Screening refers to a brief, formal, standardized evaluation for early identification of patients with developmental and behavioral deviations from the norm that are suggestive of ASD. (See 'Terminology' above.)
●Benefits and challenges – Surveillance and screening aid in the early identification of ASD, which is an important step in optimizing outcomes, but are challenging due to the time constraints of a typical office visit, the variability of the signs and symptoms of ASD in individual children, and other factors. (See 'Benefits of early identification' above and 'Challenges of early identification' above.)
●ASD surveillance – Surveillance of ASD consists of routine developmental and behavioral assessment and identification of early ASD indicators (table 2). Symptoms of ASD usually are present by 18 to 24 months of age but may not be fully apparent until three years of age. However, symptoms can present before 18 months of age. It is important for the primary care clinician to elicit and address parents'/caregivers' concerns about ASD (table 1). (See 'Surveillance and early indicators of ASD' above.)
●Approach to ASD screening
•Symptomatic children – All children with clinical findings suggestive of ASD identified on surveillance should undergo evaluation for ASD. An ASD-specific screening tool can be used as part of this assessment. (See 'Evaluation of symptomatic children' above and "Autism spectrum disorder in children and adolescents: Evaluation and diagnosis", section on 'Role of the primary care clinician'.)
•Asymptomatic children – For children without clinical findings of ASD, including those with risk factors associated with ASD (eg, a sibling diagnosed with ASD, a genetic condition associated with ASD), we suggest ASD-specific screening during early childhood (Grade 2C). We perform screening at age 18 and 24 months by using an ASD-specific screening tool. Routine early screening for ASD can prompt referral for diagnostic evaluation, which in turn leads to earlier identification and intervention. (See 'Universal screening for asymptomatic children' above.)
•Screening tools - ASD-specific screening tools (table 6) are discussed in detail separately. (See "Autism spectrum disorder in children and adolescents: Screening tools".)
●Managing children who screen positive – Management of children who screen positive for ASD includes (see 'Referrals and evaluation' above):
•Referral for early developmental services
•Comprehensive evaluation, preferably by a clinician or team that has expertise in the diagnosis and management of ASD
•Monitoring for conditions associated with ASD
●Managing children who screen negative – Children who screen negative for ASD at 18 or 24 months of age and who do not have findings of ASD should continue to undergo routine developmental and behavioral surveillance and screening. Those who have clinical findings of ASD such as atypical development or impairment of social and language skills should undergo a comprehensive evaluation regardless of the results of the ASD screen. (See 'Management of children who screen negative' above.)
●Family education and support – Parents/caregivers of children in whom ASD is suspected or who screen positive for ASD should be provided with education about the implications of a positive screen and information regarding appropriate interventions, schools and therapy centers, and government or other community-based support systems. (See 'Caregiver education and family support' above and 'Resources' above.)
ACKNOWLEDGMENT —
The UpToDate editorial staff acknowledges Carolyn Bridgemohan, MD (deceased), who contributed to an earlier version of this topic review.
