Cross-cultural adaptation, validity and reliability of the Turkish version of the patient determined disease steps scale in persons with multiple sclerosis.

: Patient Determined Disease Steps (PDDS) scale is a patient-reported outcome measure to assess disability in persons with multiple sclerosis (pwMS). This scale can be used as an alternative to Expanded Disability Status Scale (EDSS) as it is a costly, more time-consuming, and clinician-based method. This study aimed to conduct Turkish translation and cross-cultural adaptation of PDDS and investigate its psychometric properties.: Turkish translation and cross-cultural adaptation of PDDS was conducted. Its psychometric properties including validity (i.e. content, criterion, and construct) and test-retest reliability (relative and absolute) were investigated in 100 pwMS.: PDDS had a significant strong correlation with EDSS (= 0.61, < .001). Regression model to predict EDSS scores from PDDS scores was significant ( < .001, = 0.67). Both PDDS and EDSS were significantly correlated with age, disease duration, walking speed and endurance, perceived impact of MS on walking, functional mobility, working memory and information processing speed, visual memory, manual dexterity, and health-related quality of life ( < .05). No significant difference was observed in the correlation coefficients of PDDS and EDSS ( > .05). Relative test-retest reliability was found high [ICC = 0.99 (95%CI = 0.99, 0.99)]. Absolute test-retest reliability was high as the Bland-Altman analyses showed no significant systematic bias between the repeated assessments. A narrow range of the limits of agreement indicated that PDDS had high stability and low variation between first and second assessments.: Turkish version of PDDS presented high validity and test-retest reliability in pwMS.