Psychometric Evaluation of the Disabilities of the Arm, Shoulder and Hand Outcome Questionnaire for Brachial Plexus Injury Using Rasch Analysis

Abstract

Background: Disabilities of the Arm, Shoulder and Hand (DASH) questionnaire is the most widely used patient-reported outcome measure (PROM) for assessment of upper extremity disability assessment. However, DASH is a multidimensional measurement with different difficulty levels and ratio apportionment of the items categorised by ordinal scale. This has caused a misinterpretation of the total disability scores. We created a modified DASH adapted to the Rasch model. The aim of this study is to compare the functional recovery and quality of life (QOL) improvement and to assess the validity of the original DASH and modified DASH between C56/C567, C5-8 and total types of brachial plexus injury (BPI) following surgical reconstruction. Methods: A total of 183 BPI patients who underwent reconstructive surgery were evaluated for functional recovery using the range of motion and power of the affected limb, and improvement in QOL with DASH. The collected data were analysed using Rasch measurement theory to detect the misfit items. The original and modified DASH were compared under the three different types of BPI after item reduction by removing the misfit items. Results: There were significant differences in functional recovery between three types of palsy. However, PROM using DASH score with or without misfit items (12 items) did not show any significant differences. Conclusions: DASH is not suitable for comparison of upper extremity disabilities even after being corrected mathematically due to the inclusion of items from many different domains unequally. Therefore, each item of the function (with or without compensation of the uninjured hand), pain and impact to the patients should be evaluated separately. Level of Evidence: Level IV (Prognostic)