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Autism From 2 to 9 Years of Age
Catherine Lord, PhD;
Susan Risi, PhD;
Pamela S. DiLavore, PhD;
Cory Shulman, PhD;
Audrey Thurm, PhD;
Andrew Pickles, PhD
Arch Gen Psychiatry. 2006;63:694-701.
Context Autism represents an unusual pattern of development beginning in the infant and toddler years.
Objectives To examine the stability of autism spectrum diagnoses made at ages 2 through 9 years and identify features that predicted later diagnosis.
Design Prospective study of diagnostic classifications from standardized instruments including a parent interview (Autism Diagnostic InterviewRevised [ADI-R]), an observational scale (Pre-Linguistic Autism Diagnostic Observation Schedule/Autism Diagnostic Observation Schedule [ADOS]), and independent clinical diagnoses made at ages 2 and 9 years compared with a clinical research team's criterion standard diagnoses.
Setting Three inception cohorts: consecutive referrals for autism assessment to (1) state-funded community autism centers, (2) a private university autism clinic, and (3) case controls with developmental delay from community clinics.
Participants At 2 years of age, 192 autism referrals and 22 developmentally delayed case controls; 172 children seen at 9 years of age.
Main Outcome Measures Consensus best-estimate diagnoses at 9 years of age.
Results Percentage agreement between best-estimate diagnoses at 2 and 9 years of age was 67, with a weighted of 0.72. Diagnostic change was primarily accounted for by movement from pervasive developmental disorder not otherwise specified to autism. Each measure at age 2 years was strongly prognostic for autism at age 9 years, with odds ratios of 6.6 for parent interview, 6.8 for observation, and 12.8 for clinical judgment. Once verbal IQ (P = .001) was taken into account at age 2 years, the ADI-R repetitive domain (P = .02) and the ADOS social (P = .05) and repetitive domains (P = .005) significantly predicted autism at age 9 years.
Conclusions Diagnostic stability at age 9 years was very high for autism at age 2 years and less strong for pervasive developmental disorder not otherwise specified. Judgment of experienced clinicians, trained on standard instruments, consistently added to information available from parent interview and standardized observation.
Author Affiliations: University of Michigan, Ann Arbor (Drs Lord and Risi); University of North Carolina, Chapel Hill (Dr DiLavore); Hebrew University, Jerusalem, Israel (Dr Shulman); National Institute of Mental Health, Bethesda, Md (Dr Thurm); University of Manchester, Manchester, England (Dr Pickles).
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