Comparative Validity of Screening Instruments for Mental Distress in Zambia

BACKGROUND The recognition of mental health as a major contributor to the global burden of disease has led to an increase in the demand for the inclusion of mental health services in primary health care as well as in community-based health surveys in order to improve screening, diagnosis and treatment of mental distress. Many screening instruments are now available. However, the cultural validity of these instruments to detect mental distress has rarely been investigated in developing countries. In these countries, limited trained staff and specialized psychiatric facilities hamper improvement of mental health services. It is therefore imperative to develop a quick, low cost screening instrument that does not require specialized training. We validated different well established screening instruments among primary health care clinic attendees in Lusaka, Zambia. We also assess the face, content and criterion validity of the SRQ's and determined the most commonly reported symptoms for mental distress. METHODS The screening instruments, SRQ-20, SRQ-10 and GHQ-12 were used as concurrent criteria for each other and compared against a gold standard, DSM-IV. Their correlation, sensitivity and specificity were assessed. All instruments were administered to 400 primary health care clinic attendees. In-depth interviews were also conducted with 28 of these clinic attendees. RESULTS Both the SRQ-20 and SRQ-10 had high properties for identifying mental distress correctly with an AUC of 0.96 and 0.95 respectively while the GHQ-12 had modest properties (AUC, 0.81). The optimum cut-off points for this population were 7 and 3 for the SRQ and GHQ-12 respectively. The SRQ was also found to have good face and content validity. CONCLUSION The study establishes the utility of the SRQ-20 for detecting mental distress cases and also underscores the importance of validating instruments to suit the context of the target population. It also validates the SRQ-10 as the first reliable abbreviated and easy-to-use screening instrument for mental distress in primary health care facilities in Zambia.