This paper presented findings on the timing of identification in ASDs and its correlates using data from the largest U.S. population-based effort to date. The unadjusted median age of identification at each site in this study was older than the median ages in a prior report5
based on the same data. This discrepancy exists because the present study used survival analysis to include the 695 censored cases (27.1% of all cases) that met ASD surveillance case criteria, but had no previous record or documentation of an ASD diagnosis. The prior report computed the simple median age of identification using only cases with a known age of identification.
The variability among sites was notable, with seven sites having adjusted ages of identification significantly higher or lower than average. Geographic variability in educational practices, health care access, and use of services is not uncommon, and such variability has significant implications for decisions about the allocation of finite resources. Screening and diagnostic practices in these communities could be examined in future research to search for factors that facilitate or impede early identification.
Two findings especially relevant to policy are the unadjusted median age of identification (5.7 years) and the proportion of cases that had not been identified as having an ASD through age 8 (27.1%). Given that experienced clinicians can generally diagnose autism between the ages of 2 and 3, the gap between potential and actual age of identification (for those identified) is in the range of 2.7–3.7 years. Combined with the fact that more than one-quarter of cases were never identified as having ASD through age 8, this gap indicates significant weaknesses in the overall system of community screening and identification for ASD. Future research should examine the developmental, family, and societal consequences of late identification. Researchers also should conduct studies that help the public health community develop interventions to improve the timing of identification.
Several current efforts aim to improve the timing of identification of ASDs among young children. The American Academy of Pediatrics has published specific recommendations for ASD identification and evaluation.1
The “Learn the Signs. Act Early” campaign is a partnership between CDC and other groups focused on increasing awareness about early identification and diagnosis of autism among parents and health care providers.20
The National Medical Home Autism Initiative promotes the application of the medical home concept to children with ASDs.21
Little is known about the effect of these campaigns on appropriate and timely identification. The fact that many children are not identified until after age 5 suggests future efforts should include an emphasis on recognition and diagnosis among school-age children, not just among very young children.
The sex disparity is especially relevant to clinical practice. Females are identified at a later age despite a greater likelihood of cognitive impairment. This disparity could conceivably stem from sex differences in the clinical presentation of ASDs. However, a recent study that matched males and females with autism by age, IQ, and diagnosis found no sex differences in core autistic symptoms, but did find that females had more significant social, attention, and thought problems.22
Another recent study found higher social-competence ratings among boys with autism.23
That females are identified later despite tending to be more severely affected across a range of indicators suggests the possibility of sex bias in cultural expectations of children’s behavior or in clinical practices for screening, referral, and diagnosis. Different cultural expectations of what constitutes normative behavior in boys and girls may result in different thresholds for recognition of behavioral deviance. For instance, research has shown that shyness in girls is more socially acceptable than in boys.24
As predicted, earlier age of identification was associated with greater severity of cognitive impairment. The younger age of identification among children with early developmental regression is possibly related to this phenomenon, which is typically observable by age 2.8
The clinical presentation is relatively unambiguous, and some research indicates that autistic children with this course of development tend to be more severely impaired relative to those without this course of development.25
Children with evaluation records from both education and health sources had a significantly younger adjusted age of identification compared with those with education-only sources of records. We examined the possibility that this might be a result of differential access to education records across sites. However, no significant difference existed in the timing of identification between sites with full access to education records compared with those without this access. Another possible explanation for this finding is that greater access to multiple systems of care is an enabling factor that can facilitate earlier identification.
Significant racial differences were noted in the unadjusted Kaplan-Meier estimates and in the first two multivariable models. However, these differences were not significant in the final adjusted model when dummy indicators for sites were added. The black-white differences were negligible across all analyses. Hispanic children had later ages of identification than white children in the unadjusted analysis and the first two adjusted analyses. The time ratio for Hispanic children was 6 % lower in Model 1 (1.11) than in Model 3 (1.4). Although no large racial differences existed in the timing of identification, there were significant racial differences in whether children who meet ASD case criteria are ever identified as such by health and education professionals. In adjusted analyses from another report using a subset of these data, black children (odds ratio [OR] = 0.78; 95% confidence interval: 0.64, 0.96), Hispanic (OR = 0.75; 0.55, 0.99) or “other” ethnicity (OR = 0.65; 0.44, 0.97) were less likely than white children to have a documented ASD.26
This disparity was concentrated among children with IQ ≤ 70.
This study has some limitations. The range and quality of independent variables measuring autism symptoms, child health, family socioeconomic status, and access to health care were limited because of the use of record abstraction for the surveillance protocol. The lack of in-person contact with children also means we had no way of validating ASD diagnosis using a standard clinical assessment. Nor was there any way to directly confirm the age of identification. Because of the record abstraction methodology, information about the diagnostic history of a given child was possibly incomplete, and/or the record of a child with an earlier diagnosis was not able to be located.
This study also has several strengths. The population-based nature of the sample reduces the influence of volunteer biases found in community surveys. The size and demographic diversity of the sample allowed us to test for demographic disparities with adequate statistical power. The linkage with birth records allowed us to test hypotheses that would have been impossible otherwise.
In summary, this study examined the timing of identification among children with autism using a population-based sample from an ongoing surveillance effort. The large gap between the age at which children can be identified on the basis of best available practices and when they actually are identified suggests the substantial need for further research, innovation, and improvement in this area of practice.