Evaluation and improvement of the psychometric properties of the Hamilton Rating Scale for Depression using Rasch analysis for applying in Belarusian population

Introduction: The Hamilton Rating Scale for Depression (HAM-D) has not been tested for the psychometric properties in Belarusian population. In this regard conducting psychometric assessment of the HAM-D used in Belarusian population has special importance. The aim of this study was to investigate and improve the psychometric properties of the HAM-D applying in Belarusian population through Rasch analysis. Methods: Data from 551 Belarusian patients with confirmed diagnosis of depression were used in this study. The Partial Credit Model was used in the psychometric analysis. Results: The analysis of item-person map showed disagreement between distributions of person measures and item categories. Only 8 items had appropriate values of Rasch fit-indexes. I have improved the psychometric properties of the HAM-D. Five items with bad values of fit-indexes were recombined into two new items. New items were added to the remaining 8 items with acceptable fit-indexes values and then Rasch analysis was repeated. All items showed adequate construct validity. The person separation index (PSI) for original HAM-D was 2.32. The person reliability was 0.84. Reliability analysis of the final model included 10 items showed higher estimates: the PSI was 3.61, the number of strata rose to 5.14, the person reliability was 0.93. Conclusion: This study revealed that the HAM-D applied in Belarusian population has several psychometric problems. After removing invalid items and changing score rules of bipolar items psychometric properties of the scale were improved.