Article

The aim of this study was to carry out a psychometric analysis, using both
Classical Test Theory and Rasch analysis (RA) methods, of the Iowa Level of
Assistance Scale (ILAS) administered in patients with recent total hip
arthroplasty (THA) or total knee arthroplasty, to examine its metric properties
and provide insights for a refined version. A total of 203 patients who had
undergone THA or total knee arthroplasty were assessed using the ILAS for
assistance needed during functional activities (ILAS-funct) and need for
assistive devices (ILAS-dev) before discharge from the orthopedic ward. The
responses were psychometrically analyzed using the Classical Test Theory and RA.
Cronbach's alpha was adequate only for group comparisons (ILAS-funct, 0.82;
ILAS-dev, 0.79). The two domains (ILAS-funct and ILAS-dev) showed a good
correlation. According to RA rating scale diagnostics, ILAS-funct showed two
disordered response category thresholds: of the seven different response levels
of 'assistance', only five were appreciably discernible. All five ILAS-funct
items fitted the model and did not show either local dependence or differential
item functioning across age groups or sex. ILAS-dev presented two unused response
categories, which precluded Rasch calibration and subsequent analyses. ILAS-funct
showed sound psychometric properties, but the rating system of ILAS-funct could
be simplified, at least collapsing the response categories 5 (failed) and 6 (not
tested). In ILAS-dev, the presence of unused response categories calls for a
reconsideration of its scaling options and methods.

Langue : ANGLAIS