Abstract
BACKGROUND: Previous research using latent class analysis (LCA) identified classes of people with type 2 diabetes and specific profiles of depression and anxiety. Since LCA-derived anxious depression strongly predicts cardiovascular outcomes and mortality but cannot be applied to individuals, we developed a validated combined depression-anxiety metric, the Diabetes Anxiety Depression Scale (DADS), for potential clinical application in people with type 2 diabetes. METHODS: 1,337 participants with type 2 diabetes from the observational community-based Fremantle Diabetes Study Phase II completed the Patient Health Questionnaire 9-item version (PHQ-9) to assess symptoms of depression, and the Generalised Anxiety Disorder Scale (GADS) to assess symptoms of anxiety. A single score was calculated by adding all the PHQ-9 items and the four GADS items used for the LCA. Cut-off scores were calculated with Receiver Operating Characteristic (ROC) area under the curve (AUC). RESULTS: The optimum cut-off scores in terms of sensitivity, specificity, positive and negative predictive value were 18 points for major anxious depression and 8 points for minor anxious depression. A score of 8-17 was associated with a significantly increased incidence of coronary heart disease, whereas a score 18-39 was associated with an increase in both coronary heart disease and cardiovascular mortality. CONCLUSIONS: The DADS has strong psychometric validity in the identification of mixed depression-anxiety in type 2 diabetes, and may contribute to cardiovascular risk prediction.