Validation of Shona Symptom Questionnaire (SSQ-14), Patient Health Questionnaire (PHQ-9) and Generalised Anxiety Disorder scale (GAD-7) in Unguja Island, Zanzibar

Due to the dearth of resources in low- and middle-income countries, the use of culturally appropriate and psychometrically robust screening tools for common mental disorders (CMDs) administrable by lay health workers (LHWs) is critical to both identifying people that need care and collecting prevalence data to inform policy decisions. The Shona Symptom Questionnaire (SSQ-14), Patient Health Questionnaire (PHQ-9) and Generalised Anxiety Disorder Scale (GAD-7) were validated as part of introducing the Friendship Bench in Zanzibar, Tanzania. The present cross-sectional study was conducted at two primary healthcare units. The three screening tools were translated into Swahili and administered to a random sample of 475 participants alongside a standardised clinical assessment done by a psychiatrist, the gold-standard diagnostic technique to which the performance characteristics of the tools were compared. The structural validity of the tools was assessed via confirmatory factor analysis (CFA). Reliability was measured using Cronbach’s alpha. Prevalence estimates of CMDs were derived from the clinical assessments. The optimal cut-off point for the SSQ-14 was ≥ 7 (sensitivity = 76% and specificity = 70%); for the PHQ-9 was ≥ 5 (sensitivity = 69% and specificity = 63%); and for the GAD-7 was ≥ 3 (sensitivity = 69% and specificity = 64%). The area under the receiver operating characteristic curves (AUC) indicated acceptable diagnostic accuracy, i.e., AUCSSQ-14 = 0.78, AUCPHQ-9 = 0.69 and AUCGAD-7 = 0.70. CFA yielded two- and one-factor structures for the PHQ-9 and GAD-7, and SSQ-14 respectively. The internal reliability of the tools was high, i.e.,αSSQ-14 = 0.82, αPHQ-9 = 0.81 and αGAD-7 = 0.83. The prevalence of CMDs, depression, and anxiety was of 25%, 18% and 8% respectively. The tools are recommended for use by lay health workers in this setting and population. The high prevalence of CMDs reported highlights the importance of implementing evidence-based psychological interventions delivered by LHWs and reinforces the need for simple, validated, and culturally appropriate screening tools administrable by LHWs to do so, especially in low-resourced settings.