Major Depressive Disorder (MDD) is frequent in the Accident and Emergency Department (AED) but is often unrecognized. We aimed to assess the prevalence of MDD and determine the psychometric properties of the PHQ-9 in diagnosing MDD in patients with long-term medical conditions attending an AED.
The PHQ-9 was administered to 349 patients with diabetes, COPD and chronic inflammatory rheumatic diseases, mainly rheumatoid arthritis and spondyloarthropathies, visiting an AED. The MINI interview was used as the criterion standard for MDD. Receiver operator characteristic (ROC) curve analysis was performed to determine the optimal PHQ-9 cutpoint for MDD. Construct validators included psychological distress (SCL-90-R), illness perceptions (B-IPQ) and Health-Related Quality of Life (WHOQOL-BREF).
The prevalence of MDD was 27.2%. At an optimal cutpoint of 8, PHQ-9 had a sensitivity of 90.5% and specificity of 89.4%. The area under the curve (0.96) was excellent. Convergent validity was established by the strong associations between PHQ-9 scores and functional status, SCL-90-R depression, illness perceptions and AED visits during the previous year.
The sample consisted of multiple rather a single disease group, preventing us from accounting for illness severity using specific disease severity indices.
MDD is frequent in patients with long-term medical conditions attending the AED and the PHQ-9, at a cutpoint of 8, is an accurate, reliable and valid measure for MDD screening in this patient population.