Purpose: The detection of patients with comorbid mental illness is of high clinical importance in orthopaedic rehabilitation. To simplify detection of cases, screening instruments are recommended. The study investigated the discriminant validity of the Hospital Anxiety and Depression Scale (HADS) and the General Health Questionnaire (GHQ-12) to identify patients with comorbid mental disorders, specifically anxiety, depressive and somatoform disorders.
Method: Two hundred and six patients with musculoskeletal disease from four orthopaedic rehabilitation clinics participated in a two-stage survey: (1) patients were assessed with the GHQ-12 and HADS; and (2) they were examined for DSM-IV mental disorders by clinical standardized interview (CIDI). Validity of the two instruments regarding the detection of mental disorders was compared using ROC-analysis and CIDI-diagnoses as criteria.
Results: The HADS sumscale performed better in all analyses compared to the GHQ-12, specifically in detecting depressive and anxiety disorders. Best results are achieved for depressive disorders with an area under the curve (AUC) of 0.79, a sensitivity of 78% and a specificity of 71% (cut off point= 16). The positive predictive value (PPV) is best for the detection of any mental disorder with a cut-off point of 16 (46%).
Conclusion: The HADS can be used as a screening instrument for the detection of comorbid depressive and anxiety disorders in patients with musculoskeletal disorders. Limitations in performance of screening instruments are due to: (1) different methodological approaches of tests (dimensional approach) and criterion (categorical approach); and (2) difficulties in diagnosing mental disorders in patients with prominent physical illness.