Background: Depression is common in patients with cardiac disease; however, the use of depression-specific health instruments is limited by their increased responder and analyst burden. The study aimed to define a threshold value on the Short Form-36 (SF-36) mental component summary score (MCS) that identified depressed cardiac patients as measured by the Centre for Epidemiologic Studies Depression Scale (CES-D).
Methods: An optimal threshold was determined using receiver-operating characteristic (ROC) curves on SF-36 and CES-D data from a large cardiac cohort (N = 1,221). The performance of this threshold was evaluated in a further two cardiac populations.
Results: In the index cohort, an SF-36 MCS score of ≤45 was revealed as an optimal threshold according to maximal Youden Index, with high sensitivity (77%, 95% CI = 74-80%) and specificity (73%, 95% CI = 69-77%). At this threshold, in a second sample of hospital cardiac patients, sensitivity was 93% (95% CI = 76-99%) and specificity was 64% (95% CI = 49-77%). In a final sample generated from a community population, specificity was 100% (95% CI = 85-100%) and sensitivity was 68% (95% CI = 61-74%) at the cut-off of 45.
Conclusion: The SF-36 MCS may be a useful research tool to aid in the classification of cardiac patients according to the presence or absence of depressive symptoms.