Reliability and validity of PHQ-9 when administered by health workers for depression screening among women in primary care.

Background: Depression is twice more prevalent among women but remains unidentified in primary care.

Objective: We aimed to estimate the reliability and validity of PHQ-9, when administered by health workers, a cadre of public health staff, posted in primary health centres. We translated PHQ-9 to Malayalam, a language spoken by 30 million people in Kerala, India. Health workers administered PHQ-9 to women (n = 238) aged 18-60 years in a high prevalent primary care setting. Mini International Neuropsychiatric Interview (MINI) was administered by the psychiatrist on the same day to diagnose depressive disorder. Two health workers administered PHQ-9, independently, in a subset of 21 women.

Results: The internal consistency reliability (Cronbach's alpha 0.89) and inter-rater reliability (intra class correlation coefficient, 0.94; 95% CI, 0.86-0.95) were high. On ROC analysis, area under curve was 0.92 (95% CI 0.88-0.96). For a cut-off score of ≥9, PHQ-9 had a sensitivity of 82.5%, (95% CI, 72.4-92.6), specificity of 90.1% (95% CI, 84.5-95.6%), positive predictive value of 73.4% (95% CI, 62.4-84.4%) and negative predictive value of 93.9% (95% CI, 90.2-97.6%). The accuracy was 88.2% (84.0-92.4%) and positive likelihood ratio was 8.3. Factor analysis supported a single factor, with eigen value above 1, with high loading for all items (0.73-0.79), except item related to appetite (0.58). This explained 62% of variance in the data. Prevalence of MINI diagnosed depressive disorders was 25%.

Conclusion: When administered by health workers, PHQ-9 has good reliability and at cut off score ≥9, it has good validity to identify depression in primary care.