Abstract
Purpose To examine the psychometric properties of the Arabic version of the Lower Extremity Functional Scale (LEFS-Ar) in people with chronic obstructive pulmonary disease (COPD). Materials and methods Stable individuals with COPD (N = 70) confirmed by spirometry were asked to complete the LEFS-Ar, St George's Respiratory Questionnaire (SGRQ) and performed the Six-Minute Walk Test (6MWT). Participants were also asked to complete LEFS-Ar for the second time within 10 days. The LEFS-Ar floor and ceiling effects, internal consistency, test-retest reliability, measurement error, and construct validity were examined. Results The LEFS-Ar had excellent internal consistency with Cronbach's alpha of 0.95 and excellent test-retest reliability (ICCagreement=0.91) with no floor and ceiling issues. Standard error of measurement was 4.78 points while the minimal detectable change at 90% confidence was 11.15 points. Consistent with our hypotheses, the LEFS-Ar scores correlated significantly with 6MWT (r= -0.66, p < 0.001), activity domain of the SGRQ (r = 0.55, p < 0.001), and were significantly different according to COPD disease severity (p= 0.02). Conclusions In people with COPD, the LEFS-Ar has excellent reliability with no floor or ceiling effects. The LEFS-Ar demonstrated evidence supporting its validity as a measure of activity limitation that can be used in clinical practice and in research studies.