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|Title: ||The Development of a Short Measure of Physical Function for Knee OA - KOOS-Physical Function Short-form (KOOS-PS) – An OARSI/OMERACT Initiative|
|Authors: ||Perruccio, A.V.|
|Keywords: ||knee osteoarthritis; physical function; outcome measure.|
|Issue Date: ||2008|
|Publisher: ||Osteoarthritis and Cartilage|
|Citation: ||Osteoarthritis and Cartilage, 2008; 16: 542-550|
|Abstract: ||Objective: To develop a short measure of physical function for knee osteoarthritis (OA) using
multi-national data from individuals with varying degrees of severity of knee OA.
Methods: Rasch analysis, based on the partial credit model, was conducted on KOOS/WOMAC
data from individuals with knee OA, ranging from community to pre-total knee replacement
samples from 5 countries. Fit of the data to the Rasch model was evaluated by overall model fit
and item-level fit statistics (chi-square, size of residual, F-test). Invariance across age, gender
and country was evaluated. Unidimensionality was evaluated by factor analysis of residuals. The
derived short measure was further tested for fit through re-analyses in individual sub-samples. A
nomogram converting raw summed scores to Rasch-derived interval scores was developed.
Results: Thirteen data sets were included (n=2145), with an age range of 26 to 95 years, and a
male/female ratio of 1:1.4. The final model included seven of the original 22 items. From easiest
to most difficult, the items (logit) were: rising from bed (1.366), putting on socks/stockings
(1.109), rising from sitting (0.537), bending to the floor (0.433), twisting/pivoting on injured
knee (-0.861), kneeling (-1.292) and squatting (-1.292). Sub-sample analyses confirmed findings.
Conclusion: Based on the use of accepted Rasch-based measurement methods and the
compliment of countries, languages and OA-severity represented in this study, our seven item
short measure of physical function for knee OA is likely generalizable and widely applicable.
This measure has potential for use as the function component in an OA severity scoring system.|
|Appears in Collections:||UofT Faculty publications|
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