The role of comorbidity in the detection of psychiatric disorders with checklists for mental and physical symptoms in primary care

Objective To examine the contribution of a mental and physical symptom count to the detection of single or comorbid anxiety, depressive and somatoform disorders. Method In primary care 1,046 consulting patients completed the Hospital Anxiety and Depression Scale (HADS) and the Physical Symptom Checklist (PSC-51). In a stratified sample of 473 patients DSM-IV psychiatric disorders were assessed using the WHO-SCAN interview. The diagnostic value of the HADS total score and the PSC-51 symptom count was examined with ROC-analyses. Results The discriminative power of PSC-51 and HADS was highest for patients with both a somatoform disorder and an anxiety or depressive disorder, with an AUC of 0.86 (95% CI: 0.81–0.91) and 0.91 (95% CI: 0.87–0.94) respectively. Using both symptom counts together did not increase the diagnostic value for the detection of the psychiatric disorders. Conclusion Both symptom counts preferentially detected patients with comorbid disorders. When interpreting diagnostic values of screening questionnaires one should keep in mind that the validity of these values can be dependent of the presence of comorbid disorders.