Validity of the PHQ-9 and PHQ-2 to screen for depression in nationwide primary care population in Latvia.

Background: Depression is highly underdiagnosed in primary care settings in Latvia. Screening for depression in primary care is potentially an efficient way to find undetected case s and improve diagnostics. We aimed to validate both a nine-item and two-item Patient Health Questionnaire (PHQ-9 and PHQ-2) in the Latvian and Russian languages in primary care settings using a representative sample in Latvia.

Materials and methods: The study was carried out within the framework of the National Research Program BIOMEDICINE to assess the prevalence of mental disorders at 24 primary care facilities. During a 1-week period, all consecutive adult patients were invited to complete the PHQ-9 and PHQ-2. Criterion validity was assessed against the Mini International Neuropsychiatric Interview (MINI).

Results: There were 1467 patients who completed the PHQ-9 and the MINI. Overall, the PHQ-9 items showed good internal reliability (Cronbach's alpha 0.81 for Latvian version and 0.79 for Russian version of the PHQ-9). A cut-off score of 8 or greater was established for the PHQ-9 (sensitivity 0.75 and 0.79, specificity 0.84 and 0.80 for Latvian and Russian languages, respectively). For the PHQ-2, a score of 2 or higher (sensitivity 0.79 and 0.79, specificity 0.65 and 0.67 for Latvian and Russian languages) detected more cases of depression than a score of 3 or higher.

Conclusions: We suggest GPs ask patients to respond to the first 2 questions of the PHQ-9. If their score is positive, the patients should then complete the PHQ-9.