Utility and limitations of PHQ-9 in a clinic specializing in psychiatric care

Abstract

Background: The Patient Health Questionnaire-9 (PHQ-9), despite its excellent reliability and validity in primary care, has not been examined for administration to psychiatric patients. This study assesses the accuracy of PHQ-9 in screening for major depressive episode and in diagnosing major depressive episode in patients of a psychiatric specialty clinic.Methods: We compared operational characteristics of PHQ-9 as a screening and diagnostic instrument to DSM-IV-TR diagnosis by a trained psychiatrist as a reference standard. The reference criteria were " current major depressive episode" or " current major depressive episode with major depressive disorder" . PHQ-9 was used with two thresholds: diagnostic algorithm and summary scores (PHQ-9 ≥ 10). The optimal cut-off points of PHQ-9 summary scores were analyzed using a receiver operational characteristics (ROC) curve.Results: For " current major depressive episode" , PHQ-9 showed high sensitivity and high negative predictive value at both thresholds, but its specificity and positive predictive value were low. For " current major depressive episode with major depressive disorder" , PHQ-9 also showed high sensitivity and high negative predictive value at both thresholds, but the positive predictive value decreased more than that for " current major depressive episode" . The ROC analysis showed the optimal cut-off score of 13/14 for " current major depressive episode" .Conclusions: PHQ-9 is useful for screening, but not for diagnosis of " current major depressive episode" in a psychiatric specialty clinic. © 2012 Inoue et al.; licensee BioMed Central Ltd.