Measurement properties of performance-specific pain ratings of patients awaiting total joint arthroplasty as a consequence of osteoarthritis.
OBJECTIVE
To estimate the test-retest reliability of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain sub-scale and performance-specific assessments of pain, as well as the association between these measures for patients awaiting primary total hip or knee arthroplasty as a consequence of osteoarthritis.


METHODS
A total of 164 patients awaiting unilateral primary hip or knee arthroplasty completed four performance measures (self-paced walk, timed up and go, stair test, six-minute walk) and the WOMAC. Scores for 22 of these patients provided test-retest reliability data. Estimates of test-retest reliability (Type 2,1 intraclass correlation coefficient [ICC] and standard error of measurement [SEM]) and the association between measures were examined.


RESULTS
ICC values for individual performance-specific pain ratings were between 0.70 and 0.86; SEM values were between 0.97 and 1.33 pain points. ICC estimates for the four-item performance pain ratings and the WOMAC pain sub-scale were 0.82 and 0.57 respectively. The correlation between the sum of the pain scores for the four performance measures and the WOMAC pain sub-scale was 0.62.


CONCLUSIONS
Reliability estimates for the performance-specific assessments of pain using the numeric pain rating scale were consistent with values reported for patients with a spectrum of musculoskeletal conditions. The reliability estimate for the WOMAC pain sub-scale was lower than typically reported in the literature. The level of association between the WOMAC pain sub-scale and the various performance-specific pain scales suggests that the scores can be used interchangeably when applied to groups but not for individual patients.
Ashley Halket, BA, CAT(C), MSc: Assistant Clinical Director, Sheridan College, Oakville, Ontario. At the time of the study, Ms Halket was completing her MSc at the School of Rehabilitation Science, McMaster University, Hamilton, Ontario.
Ashley
A
Halket
Paul W
PW
Stratford
Deborah M
DM
Kennedy
Linda J
LJ
Woodhouse
Gregory
G
Spadoni