This study aims to evaluate the clinical features of patients with epilepsy to assess possible correlations with higher positive diagnostic rates (PDR) from genetic testing.

Retrospective study of 1021 patients with epilepsy tested using a trio-based epilepsy panel.  Testing included concurrent sequencing and analysis of the proband and parents (trio, when available) for over 1000 epilepsy genes.

Twenty-one percent of patients had a positive result.  Patients with early-life epilepsy (seizure onset <3 years old) had a significantly higher PDR (28%) than patients with later-onset epilepsy (13%, p<.001). No significant difference in PDR was observed by seizure classification (focal 22% vs. generalized 22%) nor with seizure type (infantile spasm 20%, tonic and/or clonic 18%, febrile 22%, and myoclonic 22%), with the exception of absence seizures with a notably lower PDR (13%).  Patients who were reported to have other neurodevelopmental features had a significantly higher PDR compared to patients with isolated seizures (26% vs. 13%, p<.00001). The PDR for some of these specific neurological comorbidities included: global delays (30%), delayed speech/language (28%), epileptic encephalopathy (28%), and intellectual disability (27%). Trio testing resulted in a significantly higher PDR compared to proband-only cases (24% vs. 12% p<.05).  The highest PDR was observed for patients tested as a trio, with seizure onset <3 years old, and who presented with additional neurological features (34%, 67/195).