Article

OBJECTIVES: To replicate previous Rasch analysis (RA) that yielded the 7-item
Physical Function Short Form of the Knee Injury and Osteoarthritis Outcome Score
(KOOS-PS7) in order to verify the consistency of the item selection process, and
to analyze its main psychometric properties in a sample of Italian patients with
osteoarthritis (OA). DESIGN: Methodological research on cross-sectional data from
a convenience sample. SETTING: University hospital. PARTICIPANTS: Outpatients
with symptomatic OA of the knee (N=200; women, 73%; mean age, 69.4y).
INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURE: The KOOS-PF22 (22 items
comprising the 2 KOOS domains of activities of daily living and
sport/recreation). Its dimensionality was investigated using exploratory factor
analysis. RA was performed on KOOS-PF22, KOOS-PS7, and an item set (called
KOOS-PS12) obtained by removing from KOOS-PF22 all misfitting items. RESULTS:
KOOS-PF22 showed a 2-factor structure, with the first one largely prevailing. Ten
of its 22 items did not fit the Rasch model, while item dependency was present in
7 item pairs. Five of 7 KOOS-PS7 items and all KOOS-PS12 items showed acceptable
fit to the Rasch model. The person separation reliability was .79 for KOOS-PS7
and .90 for KOOS-PS12; Cronbach alpha was .81 for KOOS-PS7 and .92 for KOOS-PS12.
CONCLUSIONS: RA was not able to replicate the selection process of the items
included in KOOS-PS7. KOOS-PS7 reliability levels indicate that the instrument
seems more useful for group decisions than for everyday clinical application in
single patients. To achieve a short form of KOOS-PF22 valid for a wide spectrum
of individuals with knee OA, further psychometric studies are warranted.
CI - Copyright (c) 2013 American Congress of Rehabilitation Medicine. Published by
Elsevier Inc. All rights reserved.

Langue : ANGLAIS