Psychometric properties of the Iranian version of the wheelchair seating discomfort assessment tool (WcS-DAT) - section II: a revised two-dimensional structure of comfort and discomfort to improve inclusive design practice.

PURPOSE: The objectives of the study were to: 1) validate the Wheelchair Seating Discomfort Assessment Tool (WcS-DAT - section II) in Iran, and 2) to determine whether or not the items on the scale address just one dimension (e.g., discomfort).

METHODS: A descriptive-methodological study was performed among 109 (76 males and 33 females) full-time wheelchair users, aged 12-70 years in Tabriz, Iran. To develop the revised Iranian version of the WcS-DAT - section II, a standard "forward-backward" method was in the first step. Then, the content validity and construct validity of the tool was assessed based on feedback from an expert panel and factor analyses (exploratory and confirmatory), respectively. Sensitivity (using ceiling/floor effect), internal consistency (using Cronbach's α), and test-retest reliability (using Intraclass Correlation Coefficient - ICC) were also evaluated.

RESULTS: Results established content validity, sensitivity, internal consistency (values of Cornbrash's α: 0.79-0.82), and test-retest reliability (values of ICC: 0.79-0.93) of the Iranian WcS-DAT - section II. Factor analyses revealed a two-factor structure (comfort and discomfort), for the scale, and thus confirmed its construct validity.

CONCLUSIONS: The findings suggest that the Iranian version of WcS-DAT- section II is a reliable and valid tool for the evaluation of wheelchair seating comfort and discomfort in the Iranian population. The revised two-factor model of comfort/discomfort has potential implications for inclusive design research and practice.