Objective: Test equivalence of different survey instruments to diagnose depression and to assess its severity. Where equivalence exists, describe how to convert scores between instruments.
Study design: Cross-sectional analysis of six convenience samples consisting of 71 members of a health plan and 107 patients of mental health specialty practices with psychiatric diagnoses were compared using the Beck Depression Inventory (BDI) and one or more of the Primary Care Screener for Affective Disorder, Prime-MD-PHQ, Inventory to Diagnose Depression, the depression subscale of the Psychiatric Diagnostic Screening Questionnaire, and the Mental Health Inventory from the SF-36.
Results: Correlations between the screening instruments and the BDI ranged from 0.79 to 0.95 and the sensitivity to depression and the specificity against nondepressive mental health diagnoses was equally good or better. We also describe a method for equating severity scores across instruments and labeling the screener-based severity measures with clinically meaningful descriptions comparable to those used for the BDI.
Conclusions: Screener-based severity measures extensively overlap each other. Good screeners for depression can also be good severity instruments. Exploiting screeners as severity instruments can significantly reduce response burden without sacrificing performance.