Translation and psychometric evaluation of the Persian version of Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS)

Abstract

Background: The present study aimed to translate and validate the Knee Outcome Survey-Activities of Daily Living Scale (KOS-ADLS) in Iran.

Methods: Following standard forward and backward translation procedure, content and face validity were tested by specialists and a sample of 32 patients. Then, in a cross sectional study, a sample of patients with knee disorders, recruited through simple sampling, completed the KOS-ADLS and the Short-Form Health Survey (SF-36) in their first visit to physiotherapy clinics in Tehran. Regarding construct validity, the Spearman's correlation (r_s) and one-way ANOVA were employed to evaluate the correlations between the Persian KOS-ADLS and SF-36 subscales (convergent validity) and known groups comparison, respectively. Test-retest reliability and internal consistency were evaluated by intraclass correlation coefficient (ICC) and the Cronbach's α coefficient.

Results: In total 101 patients were included in the study. The mean age of patients was 42.39 (SD = 9.2). The finding indicated that the KOS-ADLS had strong correlations with SF-36 physical functioning, bodily pain subscales, and also physical component summary while it had lower correlations with other subscales of the SF-36 as expected. The KOS-ADLS was able to differentiate between the subgroups of patients who differed in BMI. The acceptable level of intraclass correlation coefficient (ICC = 0.91) and Cronbach's α coefficient (α = 0.91) was obtained for the Persian KOS-ADLS. Also no floor and ceiling effects were observed for the questionnaire.

Conclusions: The Persian version of KOS-ADLS was found to be a reliable and valid outcome measure for assessing daily living activities in patients who suffer from knee pathological conditions.

Keywords: ADLS; Cross-cultural adaptation; Knee outcome survey; Persian version; Reliability; Validation.