Diagnostic accuracy of case-finding questions to identify perinatal depression.

BACKGROUND Guidelines for perinatal mental health care recommend the use of two case-finding questions about depressed feelings and loss of interest in activities, despite the absence of validation studies in this context. We examined the diagnostic accuracy of these questions and of a third question about the need for help asked of women receiving perinatal care. METHODS We evaluated self-reported responses to two case-finding questions against an interviewer-assessed diagnostic standard (DSM-IV criteria for major depressive disorder) among 152 women receiving antenatal care at 26-28 weeks' gestation and postnatal care at 5-13 weeks after delivery. Among women who answered "yes" to either question, we assessed the usefulness of asking a third question about the need for help. We calculated sensitivity, specificity and likelihood ratios for the two case-finding questions and for the added question about the need for help. RESULTS Antenatally, the two case-finding questions had a sensitivity of 100% (95% confidence interval [CI] 77%-100%), a specificity of 68% (95% CI 58%-76%), a positive likelihood ratio of 3.03 (95% CI 2.28-4.02) and a negative likelihood ratio of 0.041 (95% CI 0.003-0.63) in identifying perinatal depression. Postnatal results were similar. Among the women who screened positive antenatally, the additional question about the need for help had a sensitivity of 58% (95% CI 38%-76%), a specificity of 91% (95% CI 78%-97%), a positive likelihood ratio of 6.86 (95% CI 2.16-21.7) and a negative likelihood ratio of 0.45 (95% CI 0.25-0.80), with lower sensitivity and higher specificity postnatally. INTERPRETATION Negative responses to both of the case-finding questions showed acceptable accuracy for ruling out perinatal depression. For positive responses, the use of a third question about the need for help improved specificity and the ability to rule in depression.