Objectives: Monitor the frequency of epilepsy among children with ASD ascertained from the general population over time and compare two methods for determining co-occurring epilepsy among ASD cases.
Methods: Confirmed cases of ASD identified as part of the Missouri ADDM 2006 study year (children born 1998 and who were 8 years of age in 2006 and ascertained in the 5-county region in and around St. Louis, Missouri) were evaluated for epilepsy via the EEG lab-based surveillance system. The epilepsy surveillance system collected data from all EEG laboratories in the study area that performed EEGs on children, as well as records of clinicians who ordered the EEGs and/or who made clinical diagnostic decisions related to epilepsy. A pediatric neurologist with expertise in clinical neurophysiology and epilepsy reviewed all clinical and EEG data for each child identified through the epilepsy surveillance system. Epilepsy case status was assigned using standardized criteria for epilepsy diagnosis and classification. Alternatively, during routine data collection for ASD, abstractors (with no medical training) recorded co-occurrence of epilepsy (Yes, No, Suspected) based on information contained in the records. No additional expert review was conducted.
Results: 321 children with ASD were ascertained via the ADDM surveillance system in Missouri (estimated ASD prevalence of 12.1 per 1000; 95% CI =10.8, 13.5). 28 (8.7%) ASD cases had co-occurring epilepsy based on the EEG lab-based surveillance method. 30 (9.3%) ASD cases were determined to have epilepsy based solely on the presence of information obtained during routine data collection for ASD surveillance. The routine data collection method identified 3 epilepsy cases and 22 suspected cases that were not identified through the EEG lab-based surveillance method whereas the EEG lab-based surveillance method identified 3 epilepsy cases that were not identied as such by the routine data collection method.
Conclusions: The two methods used to ascertain co-occurring epilepsy among ASD cases yielded similar results. Furthermore, the prevalence of co-occurring epilepsy (based on the EEG lab surveillance) among 8 year-old children in 2006 with ASD is similar to the 8.9% found among 8 year-old ASD cases in 2002 using the same EEG lab-based methodology.