Article

OBJECTIVE: To investigate dimensionality and the measurement properties of the
Italian Lower Extremity Functional Scale using both classical test theory and
Rasch analysis methods, and to provide insights for an improved version of the
questionnaire. DESIGN: Rasch analysis of individual patient data. SETTING: Rehabilitation centre. PARTICIPANTS: A total of 135 patients with musculoskeletal
diseases of the lower limb. RESULTS: Patients were assessed with the Lower
Extremity Functional Scale before and after the rehabilitation. Rasch analysis
showed some problems related to rating scale category functioning, items fit, and
items redundancy. After an iterative process, which resulted in the reduction of
rating scale categories from 5 to 4, and in the deletion of 5 items, the
psychometric properties of the Italian Lower Extremity Functional Scale improved.
The retained 15 items with a 4-level response format fitted the Rasch model
(internal construct validity), and demonstrated unidimensionality and good
reliability indices (person-separation reliability 0.92; Cronbach's alpha 0.94).
Then, the analysis showed differential item functioning for six of the retained
items. The sensitivity to change of the Italian 15-item Lower Extremity
Functional Scale was nearly equal to the one of the original version (effect
size: 0.93 and 0.98; standardized response mean: 1.20 and 1.28, respectively for
the 15-item and 20-item versions). CONCLUSION:
The Italian Lower Extremity
Functional Scale had unsatisfactory measurement properties. However, removing
five items and simplifying the scoring from 5 to 4 levels resulted in a more
valid measure with good reliability and sensitivity to change.

Langue : ANGLAIS