Objectives: Investigate (1) ASD behavioral phenotype and associated developmental, medical, and psychiatric conditions with a special focus on identifying distinct symptom profiles to guide etiologic analysis and (2) genetic and environmental risk factors, with emphasis on immunologic, hormonal, medical, and sociodemographic characteristics.
Methods: Case–control design with population-based ascertainment of children aged 2–5 years with an ASD and children in two control groups&hibar;one from the general population (POP) and one with non-ASD developmental problems (DD). Potential ASD and DD children are ascertained through multiple sources using a broad diagnostic net to ensure that both diagnosed and undiagnosed ASD children are identified. POP children are identified from birth certificates. Potential participants are contacted via written invitation followed by telephone contact for eligibility and ASD screening. The Social Communication Questionnaire (SCQ) is administered to all participants to determine which children require full clinical evaluation to determine final ASD classification. Final classifications are dependent on the child’s ascertainment source (broad diagnostic net or birth certificate), SCQ results and, when indicated, results from the Autism Diagnostic Observation Schedule (ADOS) and the Autism Diag nostic Interview–Revised (ADI-R). Participant data are from parent-completed questionnaires, interviews, clinical evaluations, biospecimen sampling (blood samples, dried blood spot cards, hair, buccal swabs), and medical record abstraction. Systematic quality control (QC) is conducted for each contact with participants. Health and education professionals, voluntary organizations, and parents were engaged in SEED development and implementation.
Results: Enrollment was initiated in late 2007. Among 19,682 ASD/DD and 24,279 POP families for whom the invitation process has been finalized: 63% ASD/DD and 68% POP families never responded to the written invitation or invitation call (in 77% ASD/DD and 80% POP non-responders, accuracy of contact information was unknown); 10% ASD/DD and 12% POP children exceeded the eligible age limit before contact could be made; 27% ASD/DD and 20% POP families were contacted by telephone. Among 5, 263 ASD/DD and 4,879 POP families with telephone contact: 34% ASD/DD and 39% POP families refused; 22% ASD/DD and 35% POP families were ineligible; 43% of ASD/DD and 25% POP families consented to participate. Among 3,576 participants, 972 of 1,525 (64%) in the ASD workflow and 1,344 of 2,051 (66%) in the DD/POP workflow were assigned a final study group classification: 600 Final ASD (of which 116 (19%) did not have a previous ASD diagnosis), 83 Possible ASD, 835 Final DD, 798 Final POP.
Conclusions: The richness of SEED’s detailed phenotype, environment, genetic, and biomarker data and the large, well-defined study sample will permit the simultaneous investigation of numerous genetic, environmental and phenotypic features and their interplay.
See more of: Epidemiology
See more of: Prevalence, Risk factors & Intervention