Psychometric evaluation of the Major Depression Inventory (MDI) as depression severity scale using the LEAD (Longitudinal Expert Assessment of All Data) as index of validity.

BACKGROUND The Major Depression Inventory (MDI) was developed to cover the universe of depressive symptoms in DSM-IV major depression as well as in ICD-10 mild, moderate, and severe depression. The objective of this study was to evaluate the standardization of the MDI as a depression severity scale using the Visual Analogue Scale (VAS) as index of external validity in accordance with the LEAD approach (Longitudinal Expert Assessment of All Data). METHODS We used data from two previously published studies in which the patients had a MINI Neuropsychiatric Interview verified diagnosis of DSM-IV major depression. The conventional VAS scores for no, mild, moderate, and severe depression were used for the standardization of the MDI. RESULTS The inter-correlation for the MDI with the clinician ratings (VAS, MES, HAM-D17 and HAM-D6) increased over the rating weeks in terms of Pearson coefficients. After nine weeks of therapy the coefficient ranged from 0.74 to 0.83. Using the clinician-rated VAS depression severity scale, the conventional MDI cut-off scores for no or doubtful depression, and for mild, moderate and severe depression were confirmed. CONCLUSIONS Using the VAS as index of external, clinical validity, the standardization of the MDI as a measure of depression severity was accepted, with an MDI cut-off score of 21 for mild depression, 26 for moderate depression severity, and 31 for severe depression. TRIAL REGISTRATION Martiny et al. Acta Psychiatr Scand 112:117-25, 2005: None - due to trial commencement date. Straaso et al. Acta Neuropsychiatr 26:272-9; 2014: ClinicalTrials.gov ID NCT01353092 .