RESUMEN
BACKGROUND AND PURPOSE: The aim of this study was to determine the face and criterion validity, stability reliability, and internal consistency of the Persian version of the Impact on Participation and Autonomy (IPA-p) scale among Iranian people with multiple sclerosis (MS). METHODS: Trained experts interviewed 364 MS patients and their relatives to assess the criterion validity, stability reliability, and internal consistency of the IPA-p scale. Ten specialists from different disciplines were also recruited to assess its face validity. A consent form was completed by the patients and their relatives. Internal consistency reliability was measured using Cronbach's alpha and stability reliability was assessed using interclass correlation coefficients (ICCs). The test-retest method was used to detect the reliability of the questioner. The study subjects completed the IPA-p scale on two occasions separated by an interval of 30-45 days. Study checklists were also used to assess the face validity, stability reliability, and internal consistency of the IPA-p scale. RESULTS: About 50% of the respondents reported their perceived overall participation to be "good" or "very good" and 60% of the specialists rated the ability of the IPA-p scale to measure what it was designed for as "excellent." Spearman correlation coefficients were >0.8 for all but one IPA-p domain. Cronbach's alpha between the mean IPA-p scale scores achieved on two separate occasions ranged from 0.858 to 0.913. The highest and lowest internal consistencies belonged to the "social relationships" and "education and learning" domains, respectively. The test-retest ICCs for the nine domains were between 0.789 and 0.919, and all were significant at p<0.001. CONCLUSIONS: The IPA-p questionnaire can be considered a valid and reliable instrument for assessing self-reported participation among Iranian MS patients.