Validity of the Patient Health Questionnaire (PHQ)-9 and PHQ-2 in general internal medicine primary care at a Japanese rural hospital: a cross-sectional study

Objective

Two depression screening tools, Patient Health Questionnaire (PHQ)-9 and PHQ-2, have not had their validity examined in general internal medicine settings in Japan. We examined the validity of these screening tools.

Methods

A total of 598 outpatients of an internal medicine clinic in a rural general hospital were enrolled consecutively and stratified by PHQ-9 score. Seventy-five patients randomly selected and 29 patients whose results from the PHQ-9 were considered to be positive for depressive disorder were then interviewed with a semistructured interview, the Mini International Neuropsychiatric Interview. We calculated diagnostic accuracy of the PHQ-9 and PHQ-2 to detect major depression and that of the suicidality item of the PHQ-9 to detect suicidality using sampling weights with multiple imputations.

Results

Sensitivity and specificity for depression were 0.86 and 0.85, respectively, for the PHQ-9 with cutoff points of 4/5, and 0.77 and 0.95, respectively, for the PHQ-2 with cutoff points of 2/3. Sensitivity and specificity of the suicidality item of the PHQ-9 were 0.70 and 0.97, respectively.

Conclusion

In internal medicine clinics in Japanese rural hospitals, the PHQ-2 with an optimal cutoff point for each setting plus the suicidality item of the PHQ-9 can be recommended to detect depression without missing suicidality.