Objective: Depression is common but frequently undetected in patients with coronary artery disease (CAD). Self-report screening instruments for assessing depression such as the Hospital Anxiety and Depression Scale (HADS) and the Patient Health Questionnaire-9 (PHQ-9) are available but their validity is typically determined in depressed patients without comorbid somatic illness. We investigated the validity of these instruments relative to a referent diagnostic standard in recently hospitalized patients with CAD.
Method: Three months post-discharge for a cardiac admission, 193 CAD patients completed the HADS and PHQ-9. The Mini International Neuropsychiatric Interview (MINI) was the criterion standard. Scale reliability was calculated using Cronbach's alpha. Convergent validity was computed using Pearson's intercorrelations. Sensitivity and specificity for various cut-off scores for both measures and for the PHQ-9 categorical algorithm were calculated using receiver operating characteristics (ROC). For analyses, participants were assigned to two groups, 'major depressive disorder' or 'any depressive disorder'.
Results: For all calculations, alpha was 0.05 and tests were two-tailed. Internal consistencies for the two measures were excellent. Criterion validity for the PHQ-9 and HADS was good. We found no statistical differences between the PHQ-9 and HADS for detecting either group; however, the categorical algorithm of the PHQ-9 for diagnosing major depression had a superior LR+ when compared with the summed HADS or PHQ-9. The operating characteristics of the screening instruments for 'any depressive disorder' were slightly lower than for 'major depressive disorder'. Some optimum cut-off scores were lower than the generally recommended cut-off scores, particularly when screening for major depression (e.g., > or = 5/6 vs. > or = 10 and > or = 8 for PHQ-9 and HADS, respectively). Lowering the cut off scores substantially improved the sensitivity of these instruments while retaining specificity, thereby improving their usefulness to screen for CAD patients with depression.
Conclusions: Both instruments have acceptable properties for detecting depression in recently hospitalized cardiac patients, and neither scale is statistically superior when summed scores are used. The categorical algorithm of the PHQ-9 for diagnosing major depression has a superior LR+ compared to the summed PHQ-9 and HADS scores. Use of the generally recommended cut-off scores should be cautious. In light of the aversive outcomes associated with depression in CAD, screening for depression is a clinical priority.