Screening for depression in a tertiary epilepsy clinic.

Symptoms of depression are common in patients with epilepsy with a reported prevalence of as high as 54%1. The fact that depression is a strong predictor of quality of life1 highlights the importance of developing effective screening tools to assist in the diagnosis of depression in the epilepsy outpatient clinic setting. Gilliam et al have reported that the Neurologic Disorders Depression Inventory in Epilepsy (NDDI-E) is an effective screening tool to detect depression in patients with epilepsy with NDDI-E scores >15 associated with a positive predictive value (PPV) of 62% for major depressive episode (MDE)2. Other researchers have also demonstrated high PPV for the NDDI-E3, however, the internal reliability of the NDDI-E has not been previously reported. While the replication of validation studies suggests that the NDDI-E is an effective tool to screen for MDE, the results are surprising given the considerable differences in phraseology between the NDDI-E and the Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition, Test Revision (DSM-IV-TR)4. Specifically in order to make a DSMIV-TR diagnosis of MDE, a patient must respond affirmatively to experiencing symptoms “most of the day, nearly every day” for five of nine questions while for the NDDI-E a positive score (>15) is possible without any response being in the “always or often” category (i.e. responding “sometimes” to all questions results in an NDDI-E score of 18). The purpose of this study was to evaluate the predictive value of the NDDI-E for MDE in an adult tertiary epilepsy clinic setting. As well, the internal reliability of the NDDI-E was also evaluated.