The criterion validity of the web-based Major Depression Inventory when used on clinical suspicion of depression in primary care

BACKGROUND The Major Depression Inventory (MDI) is widely used in Danish general practice as a screening tool to assess depression in symptomatic patients. Nevertheless, no validation studies of the MDI have been performed. The aim of this study was to validate the web-based version of the MDI against a fully structured telephone interview in a population selected on clinical suspicion of depression (ie, presence of two or three core symptoms of depression) in general practice. MATERIALS AND METHODS General practitioners (GPs) invited consecutive persons suspected of depression to complete the web-based MDI in a primary care setting. The validation was based on the Munich-Composite International Diagnostic Interview (M-CIDI) by phone. GPs in the 22 practices in our study included 132 persons suspected of depression. Depression was rated as yes/no according to the MDI and M-CIDI. Sensitivity, specificity, and positive predictive value of the International Classification of Diseases, Tenth Revision (ICD-10) algorithms of the MDI were examined. RESULTS According to the M-CIDI interview, 87.9% of the included population was depressed and 64.4% was severely depressed. According to the MDI scale, 59.1% of the population was depressed and 31.8% was severely depressed. The sensitivity of the MDI for depression was 62.1% (95% confidence interval [95% CI]: 52.6-70.9) and the specificity was 62.5% (95% CI: 35.4-84.8). The sensitivity for severe depression was 42.2% (95% CI: 30.6-52.4) and the specificity was 85.1% (95% CI: 71.7-93.8). The receiver operating curve showed an area under the curve of 0.66 (95% CI: 0.52-0.81) for any depression and of 0.72 (95% CI: 0.63-0.81) for severe depression. CONCLUSION The MDI is a conservative instrument for diagnosing ICD-10 depression in a clinical setting compared to the M-CIDI interview. Only a few false-positive diagnoses were identified when the MDI was used on clinical suspicion of depression.