Age at First Identification of Autism Spectrum Disorder: An Analysis of Two US Surveys.
OBJECTIVE
Evidence regarding the age at which autism spectrum disorder (ASD) is identified is essential for improving early detection, yet many extant studies have not applied time-to-event analyses, which account for statistical biases that arise from sampling in cross-sectional surveys by adjusting for child age at time of parental report. Our objective was to estimate age distributions for first identification of ASD in national parent surveys using time-to-event analyses.


METHODS
We conducted time-to-event analyses of responses to identical questions in the 2011 to 2012 National Survey of Children's Health (n = 95,677) and the 2009 to 2010 National Survey of Children with Special Health Care Needs (n = 371,617).


RESULTS
Parents in both surveys reported that a minority of ASD cases were identified before age 3 years, and that one-third to one-half of cases were identified after 6 years. In both surveys, a majority of parents described their child's ASD severity as mild, and these parents reported the oldest age at identification (mean, 5.6 and 8.6 years). In contrast, parents who described their child's ASD as severe reported earlier age at identification (mean, 3.7 and 4.5 years). Time-to-event analyses yielded older estimates of age at identification than analyses based on raw distributions.


CONCLUSIONS
In two national surveys, a majority of parents of children with ASD reported identification after 3 years, when eligibility for early intervention services expires, and many reported identification of ASD after school age. Later identification of children with milder symptoms highlights the need for early screening that is sensitive to all forms of ASD, regardless of severity.
Tufts Medical Center, Boston. Electronic address: rsheldrick@tuftsmedicalcenter.org.
R Christopher
RC
Sheldrick
University of Massachusetts, Boston.
Melissa P
MP
Maye
University of Massachusetts, Boston.
Alice S
AS
Carter
D000067877:Autism Spectrum Disorder / Q000175:diagnosis*; D002648:Child; D002675:Child, Preschool; D042241:Early Diagnosis; D005260:Female; D006306:Health Surveys; D006801:Humans; D008297:Male; D010290:Parents; D012720:Severity of Illness Index; D014481:United States
age at diagnosis; autism spectrum disorder; epidemiology; mass screening; survival analysis