Validation of the Patient Health Questionnaire-9 (PHQ-9) for depression screening in adults with epilepsy

•Validation of the PHQ-9 for depression screening in adults with epilepsy•Diagnostic accuracy of the PHQ-9, PHQ-2, and NDDI-E tested using the “gold standard” MINI test•High-powered prospective study at a level 4 epilepsy center with a diverse cohort•Offers free nonproprietary alternative to screen depression in adults with epilepsy•Highlights relatively underreported and treated psychiatric comorbidity in epilepsy

ObjectiveThis study aimed to assess the accuracy and operating characteristics of the Patient Health Questionnaire-9 (PHQ-9) for depression screening in adults with epilepsy.MethodsTertiary epilepsy center patients served as the study population, with 237 agreeing to structured interview using the Mini-International Neuropsychiatric Interview (MINI), a “gold standard” instrument developed for rapid diagnosis of neuropsychiatric disorders, including major depressive disorder (MDD); 172 also completed the PHQ-9, and 127 completed both the PHQ-9 and the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E) within two days of the MINI. Sensitivity, specificity, positive and negative predictive values, and areas under the ROC curves for each instrument were determined. Cut-points of 10 for the PHQ-9 and 15 for the NDDI-E were used, and ratings at or above the cut-points were considered screen-positive. The PHQ-9 was divided into cognitive/affective (PHQ-9/CA) and somatic (PHQ-9/S) subscales to determine comparative depression screening accuracy.ResultsThe calculated areas under the ROC curves for the PHQ-9 (n = 172) and the PHQ-9/CA and PHQ-9/S subscales were 0.914, 0.924, and 0.846, respectively, with the PHQ-9 more accurate than the PHQ-9/S (p = 0.002) but not different from the PHQ-9/CA (p = 0.378). At cut-points of 10 and 15, respectively, the PHQ-9 had higher sensitivity (0.92 vs 0.87) but lower specificity (0.74 vs 0.89) compared with the NDDI-E. The areas under the ROC curves of the PHQ-9 and the NDDI-E showed similar accuracy (n = 127; 0.930 vs 0.934; p = 0.864).SignificanceThe PHQ-9 is an efficient and nonproprietary depression screening instrument with excellent accuracy validated for use in adult patients with epilepsy as well as multiple other medical populations.