Scoring rules and rating formats of Self-report Depression Questionnaires: a comparison of approaches.

Self-report measures of depression differ in their construction and scoring rules. In the present study from the Rhode Island Methods to Improve Diagnostic Assessment and Services (MIDAS) project we tested the hypothesis that the loss of information due to scoring rules or rating formats reduces the validity of depression severity assessment. One hundred fifty-three outpatients with DSM-IV major depressive disorder (MDD) who presented for treatment or who were in ongoing treatment and had their medication changed due to lack of efficacy completed the Clinically Useful Depression Outcome Scale (CUDOS), Quick Inventory of Depressive Symptomatology (QIDS) and Remission from Depression Questionnaire (RDQ) at the initiation of treatment and 4 month follow-up. The patients were evaluated with the 17-item Hamilton Depression scale (HAMD). The CUDOS and RDQ were equally highly correlated with the HAMD at baseline and follow-up. There was no significant difference in the correlations between the modified and original scoring algorithms of the QIDS with the HAMD at baseline and the follow-up. On each scale, the patients showed significant levels of improvement from baseline to 4 months, and the effect sizes were similar. These findings suggest that the loss of information due to the scoring rules of the QIDS or the rating format of the RDQ did not reduce the validity of depression severity assessment.