Validation of the Utah Registry of Autism and Developmental Disabilities: A State-Wide Registry for Autism Spectrum Disorder
Objectives: 1) Validate URADD’s ascertainment of children with ASD against the Utah Autism and Developmental Disabilities Monitoring (UT-ADDM) project’s ascertainment of children with ASD. 2) Determine the impact of imposing a more stringent definition of ASD on URADD prevalence estimates, sensitivity, and specificity.
Methods: URADD uses two ascertainment methods. The first is a passive surveillance system in which individuals with ASD are identified by birth cohort based on a community medical ASD diagnosis and/or autism special education eligibility (URADD method). Second, URADD previously participated in the CDC’s ADDM Network in surveillance years (SY) 2002, 2008, 2010, and 2012. ADDM uses a retrospective record review approach to identify children who meet ASD case definition based on DSM-IV-TR criteria (UT-ADDM method). For this study, eight-year-old children identified with ASD, residing in the three county UT-ADDM surveillance area in SY2010 or SY2012 were categorized by ascertainment method: URADD, UT-ADDM, or both. ASD prevalence was estimated by ascertainment method and compared using a chi-square test. The sensitivity and specificity of URADD ASD case status was estimated using UT-ADDM as the gold standard. A more stringent URADD definition was subsequently imposed by limiting ascertainment to children with ≥ 2 medical ASD diagnoses and/or an autism special education eligibility. URADD-based ASD prevalence, sensitivity, and specificity analyses were subsequently repeated.
Results: Collectively, 872 and 1141 eight-year-old children were identified with ASD by UT-ADDM and URADD, respectively for SYs 2010/2012. 74% of eight-year-old children identified with ASD in SYs 2010/2010 were ascertained by both UT-ADDM and URADD (N=647). URADD’s ASD prevalence estimate (23/1,000 eight-year-old children (95% Confidence Interval (CI)): 22.1-24.8) was statistically significantly higher than UT-ADDM’s (18/1,000 eight-year-old children (95% CI: 16.8-19.1); p-value < 0.0001). Sensitivity and specificity of URADD case ascertainment was 81.7% and 96.4%, respectively. After removing the 263 cases ascertained by URADD based on a single medical diagnosis, URADD’s prevalence was reduced to 14.0/1,000 (95% CI: 12.9-14.9) eight-year-old children, and sensitivity and specificity of URADD versus UT-ADDM changed to 58.5% and 98.6%, respectively.
Conclusions: URADD’s high sensitivity and specificity compared with UT-ADDM validates URADD’s community-based approach to ASD case ascertainment. URADD’s approach results in higher ASD prevalence estimates than the UT-ADDM method suggesting that the URADD approach may be more susceptible to identifying persons who are false-positive for ASD. However, imposing a stricter definition of ASD on URADD resulted in a marked decrease in sensitivity and only a minimal increase in specificity. From a public health perspective, URADD’s capacity to conduct complete population-wide ASD ascertainment outweighs the risk of mis-classifying a small proportion of unaffected persons.