Comparison of two self-rating scales to detect depression: HADS and PHQ-9

Abstract

Background: More than half of patients with depression go undetected. Self-rating scales can be useful in screening for depression, and measuring severity and treatment outcome. Aim: This study compares the Hospital Anxiety and Depression Scale (HADS) and the Patient Health Questionnaire (PHQ-9) with regard to their psychometric properties, and investigates their agreement at different cut-off scores. Method: Swedish primary care patients and psychiatric outpatients (n = 737) who reported symptoms of depression completed the self-rating scales. Data were collected from 2006 to 2007. Analyses with respect to internal consistency, factor analysis, and agreement (Cohen's κ) at recommended cut-offs were performed. Results: Both scales had high internal consistency (α = 0.9) and stable factor structures. Using severity cut-offs, the PHQ-9 (≥5) diagnosed about 30% more patients than the HADS depression subscale (HADS-D; ≥8). They recognised the same prevalence of mild and moderate depression, but differed in relation to severe depression. When comparing recommended screening cut-offs, HADS-D ≥11 (33.5% of participants) and PHQ-9 ≥10 (65.9%) agreement was low (κ = 0.35). Using the lower recommended cut-off in the HADS-D (≥8), agreement with PHQ-9 ≥10 was moderate (κ = 0.52). The highest agreement (κ = 0.56) was found comparing HADS-D ≥8 with PHQ-9 ≥12. This also equalised the prevalence of depression found by the scales. Conclusion: The HADS and PHQ-9 are both quick and reliable. The HADS has the advantage of evaluating both depression and anxiety, and the PHQ-9 of being strictly based upon the Diagnostic and Statistical Manual of Mental Disorders. The agreement between the scales at the best suitable cut-off is moderate, although the identified prevalence was similar. This indicates that the scales do not fully identify the same cases. This difference needs to be further explored. ©British Journal of General Practice.