• Maria Jenelyn Alviar, John Olver, Julie F Pallant, Caroline Brand, Richard de Steiger, Marinis Pirpiris, Andrew Bucknill, and Fary Khan.
• The University of Melbourne-Royal Melbourne Hospital, Melbourne, Australia. m.alviar@pgrad.unimelb.edu.au
• J Rehabil Med. 2012 Nov 1; 44 (11): 955-61.

ObjectiveTo determine the dimensionality, reliability, model fit, adequacy of the qualifier levels, response patterns across different factors, and targeting of the International Classification of Functioning, Disability and Health (ICF) osteoarthritis core set categories in people with osteoarthritis undergoing hip and knee arthroplasty.MethodsThe osteoarthritis core set was rated in 316 persons with osteoarthritis who were either in the pre-operative or within one year post-operative stage. Rasch analyses were performed using the RUMM 2030 program.ResultsTwelve of the 13 body functions categories and 13 of the 19 activity and participation categories had good model fit. The qualifiers displayed disordered thresholds necessitating rescoring. There was uneven spread of ICF categories across the full range of the patients' scores indicating off--targeting. Subtest analysis of the reduced ICF categories of body functions and activity and participation showed that the two components could be integrated to form one measure.ConclusionThe results suggest that it is possible to measure functioning using a unidimensional construct based on ICF osteoarthritis core set categories of body functions and activity and participation in this population. However, omission of some categories and reduction in qualifier levels are necessary. Further studies are needed to determine whether better targeting is achieved, particularly during the pre-operative and during the sub-acute care period.

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