Comparing the construct validity of the Patient Health Questionnaire (PHQ-9) and the Major Depression Inventory (MDI) using Rasch analysis.

Objective: The Patient Health Questionnaire (PHQ-9) and the Major Depression Inventory (MDI) are psychometric instruments frequently used for depression diagnosis and monitoring in primary care settings. The goal of this study was to assess and compare the construct validity of the PHQ-9 and the MDI using Rasch analysis.

Methods: The PHQ-9 and the MDI were distributed in random ordering (first or last) to a waiting room sample of Danish primary care patients.