Accuracy of ICD-10-CM claims-based definitions for epilepsy and seizure type

Abstract Objective To evaluate the accuracy of ICD-10-CM claims-based definitions for epilepsy and classifying seizure types in the outpatient setting. Methods We reviewed electronic health records (EHR) for a cohort of adults aged 18+ years seen by six neurologists who had an outpatient visit at a level 4 epilepsy center between 01/2019-09/2019. The neurologists used a standardized documentation template to capture the diagnosis of epilepsy (yes/no/unsure), seizure type (focal/generalized/unknown), and seizure frequency in the EHR. Using linked ICD-10-CM codes assigned by the provider, we assessed the accuracy of claims-based definitions for epilepsy, focal seizure type, and generalized seizure type against the reference-standard EHR documentation by estimating sensitivity (Sn), specificity (Sp), positive predictive value (PPV), and negative predictive value (NPV). Results There were 673 eligible outpatient encounters. After review of EHRs for standardized documentation, an analytic sample consisted of 520 encounters representing 402 unique patients. In the EHR documentation, 93.5% (n = 486/520) of encounters were with patients with a diagnosis of epilepsy. Of those, 66.0% (n = 321/486) had ≥1 focal seizure, 41.6% (n = 202/486) had ≥1 generalized seizure, and 7% (n = 34/486) had ≥1 unknown seizure. An ICD-10-CM definition for epilepsy (i.e., ICD-10 G40.X) achieved Sn = 84.4% (95% CI 80.8-87.5%), Sp = 79.4% (95% CI 62.1-91.3%), PPV = 98.3% (95% CI 96.6-99.3%), and NPV = 26.2% (95% CI 18.0-35.8%). The classification of focal vs generalized/unknown seizures achieved Sn = 69.8% (95% CI 64.4-74.8%), Sp = 79.4% (95% CI 72.4-85.3%), PPV = 86.8% (95% CI 82.1-90.7%), and NPV = 57.5% (95% CI 50.8-64.0%). Conclusions Claims-based definitions using groups of ICD-10-CM codes assigned by neurologists in routine outpatient clinic visits at a level 4 epilepsy center performed well in discriminating between patients with and without a diagnosis of epilepsy and between seizure types.