Psychometric properties of screening questionnaires to detect depression in primary healthcare setting in rural Ethiopia

BACKGROUND: Much of the research about the validity of depression screening questionnaires is on criterion validity. Evidence is scarce on the concurrent, convergent and construct validity of these measures, particularly from low-income countries. This study aimed to evaluate the psychometric properties of depression screening questionnaires in primary healthcare (PHC) in rural Ethiopia. METHODS: A facility-based cross-sectional study was conducted with 587 participants recruited from patients attending three PHC facilities and two ‘Holy water sites’ (places where religious treatment is being provided). The psychometric properties of five mental health screening questionnaires were evaluated: the nine item Patient Health Questionnaire (PHQ-9), the two item version of PHQ-9 (PHQ-2), a version of PHQ-9 with two added items of irritability and noise intolerance (PHQ-11), the Patient Health Questionnaire-15 (PHQ-15), and the World Health Organization-Five Well-being Index (WHO-5). Clinical diagnosis of depression was ascertained by psychiatrists. We analyzed data using exploratory factor analysis, Spearman’s rank order correlation coefficient (Rho), the Mann Whitney test of the equality of medians, univariate logistic regression and Cronbach’s alpha. RESULTS: PHQ-9, PHQ-11 and WHO-5 were found to be unidimensional, with items in each scale highly loading onto one factor (factor loadings ranging from 0.64 to 0.87). The items of each instrument were internally consistent, with Cronbach’s alpha ranging from 0.72 (PHQ-2) to 0.89 (PHQ-11). Scores for all screening scales were moderately or highly correlated with each other (Rho = 0.58 to 0.98) and moderately correlated with anxiety and disability scores. Median scores of all screening scales were significantly higher in those diagnosed with depression. The association of items measuring emotional and cognitive symptoms with the diagnosis of depression was stronger than the association with items measuring somatic symptoms. Irritability and noise intolerance had higher association with depression diagnosis than PHQ-9 items. CONCLUSION: Emotional and cognitive symptoms are more useful than somatic symptoms to predict the diagnosis of depression in the PHC context in Ethiopia. Future research should focus on testing the unidimensionality of PHQ-9, PHQ-11 and WHO-5 using confirmatory factor analysis; establishing the criterion validity of PHQ-11 and WHO-5; and on assessing test-retest reliability of all the measures.