The validity of the Patient Health Questionnaire for screening depression in chronic care patients in primary health care in South Africa

BACKGROUND People with chronic health conditions are known to have a higher prevalence of depressive disorder. The Patient Health Questionnaire (PHQ-9) is a widely-used screening tool for depression which has not yet been validated for use on chronic care patients in South Africa. METHODS A sample of 676 chronic care patients attending two primary health facilities in North West Province, South Africa were administered the PHQ-9 by field workers and a diagnostic interview (the Structured Clinical Interview for DSM-IV) (SCID) by clinical psychologists. The PHQ-9 and the PHQ-2 were evaluated against the SCID, as well as for sub-samples of patients who were being treated for HIV infection and for hypertension. RESULTS Using the SCID, 11.4 % of patients had major depressive disorder. The internal consistency estimate for the PHQ-9 was 0.76, with an area under the receiver operator curve (AUROC) of 0.85 (95 % CI 0.82-0.88), which was higher than the AURUC for the PHQ-2 (0.76, 95 % CI 0.73-0.79). Using a cut-point of 9, the PHQ-9 has sensitivity of 51 % and specificity of 94 %. The PHQ-9 AUROC for the sub-samples of patients with HIV and with hypertension were comparable (0.85 and 0.86, respectively). CONCLUSIONS The PHQ-9 is useful as a screening tool for depression among patients receiving treatment for chronic care in a public health facility.