The performance of K6 as a screening tool for mood disorders: A population-based study of the São Paulo metropolitan area.

Aim: The use of screening instruments allows the detection of psychological and behavioural manifestations there are often not identified in users of health services. We evaluated the performance of the Kessler Psychological Distress Scale (K6) in identifying mood disorders (MD), using the Composite International Diagnostic Interview (CIDI) as gold-standard, in a population-based sample (n = 5037) of adult residents of metropolitan São Paulo.

Methods: Sensitivity, specificity, positive and negative predictive values, and accuracy were calculated to assess the performance of K6 in detecting 30-day CIDI MD. All cut-points for each disorder were analysed using the Youden index and the area under the receiver operating characteristic curve (AUC), and the best cut-points were identified. Cronbach's alpha was calculated to assess internal consistency.

Results: In total, 5.5% respondents screened positive for any MD (95% IC 4.84-6.14). A good detection performance was observed for all MD, with AUC values for any MD of 0.91 (95% IC 0.89-0.92), ranging from 0.80 (95% CI 0.71-0.98) for minor depression to 0.93 (95% CI 0.87-0.98) for bipolar I disorder. Best cut-points for each MD were identified, with overall sensitivity and specificity of 88.8% and 80.2%, respectively. Cronbach's alpha was 0.83.

Conclusions: K6 is a good screening tool for MD in the Brazilian population. It is a brief and easy to use instrument that can promote the early identification and treatment of MD, reducing the burden of mental illness.