Objective: The nine-item mood module of the Patient Health Questionnaire (PHQ-9) was developed to screen and to diagnose patients in primary care with depressive disorders. We systematically reviewed the psychometric literature on the PHQ-9 and performed a meta-analysis to ascertain its summary sensitivity and specificity.
Methods: EMBASE, PubMed and PsycINFO were used to search literature up to July 2006. Studies were included if (1) they investigated the diagnostic accuracy of the PHQ-9 and (2) the PHQ-9 had been compared with a reference test. The quality of the studies was appraised using the Quality Assessment of Diagnostic Accuracy Studies. We calculated sensitivity, specificity and confidence intervals for each included study. We used the random effects model to calculate the summary sensitivity and specificity.
Results: We found a sensitivity of 0.77 (0.71-0.84) and a specificity of 0.94 (0.90-0.97) for the PHQ-9. The positive predictive value in an unselected primary care population was 59%, which increased to 85-90% when the prior probability increased to 30-40%.
Conclusion: In primary care, the PHQ-9 is a valid diagnostic tool if used in selected subgroups of patients with a high prevalence of depressive disorder.