Abstracts

Rationale: Depression is common in patients with epilepsy with reported prevalence of 20-55%. Gilliam et al.(2006) have recently reported that the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) is an effective screening tool to detect depression in an outpatient epilepsy clinic setting with NDDI-E scores of >15 associated with a positive predictive value of 0.62. The purpose of this study was to confirm the effectiveness of the NDDI-E in an adult tertiary epilepsy clinic setting. Methods: The NDDI-E was administered to 63 consecutive patients (29 females) seen in the University of Alberta adult epilepsy clinic. Patients without a diagnosis of epilepsy or with developmental delay were excluded. The mean age of patients was 36 years (range:16-72). Forty-two patients were medically intractable. For patients with NDDI-E scores >12, a detailed interview was performed based on DSM- IV-TR criteria for major depressive episode. Results: The mean score for medically intractable patients was 14.4 and for seizure free patients was 11.3 (t-test p=0.003). No correlation was observed between age and NDDI-E score, nor was any sex difference in score seen. Overall NDDI-E scores were as follows: <13: 30 patients, 13-15: 15 patients, 16-18: 11 patients and >18: 7 patients. Formal DSM-IV-TR depression interview was performed on 28 of 33 patients with NDDI-E scores >12. Four of 28 patients met DSM-IV-TR criteria for major depressive episode (one patient had a NDDI-E score of 18 and the remaining three subjects had scores >18). Positive predictive value for the NDDI-E was 0.14 for a score >12, 0.24 for a score >15 and 0.43 for a score >18. Conclusions: In contrast to the report of Gilliam et al., the positive predictive value of the NDDI-E with respect to a diagnosis of major depressive episode was considerably lower in our study. While differences in study design and patient populations could have accounted for the discrepancy, our results suggest that further validation of the NDDI-E is necessary in order to develop an effective screening tool for major depressive episodes in epilepsy patients. The overall high NDDI-E scores observed in our study suggest that many epilepsy patients are experiencing symptoms of depression, which may be associated with significant comorbidity despite not fulfilling DSM-IV-TR criteria for major depressive episode.