 |
|
|
 |
The Comprehensive Osteoarthritis Test: a Simple Index for Measurement of Treatment Effects in Clinical Trials
LYNDON O. BROOKS, MARGARET I. ROLFE, PHILLIP A. CHERAS, and STEPHEN P. MYERS
ABSTRACT. Methods. Both the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and the proposed new Comprehensive Osteoarthritis Test (COAT) instrument were completed weekly by 125 subjects in the context of a randomized, 12-week, 3 parallel-arm clinical trial. The reliabilities of the various scales were assessed on a weekly basis by use of Cronbach's alpha coefficients. The validity of the COAT total scale was assessed by correlation with the WOMAC total scale on a weekly basis with correlation coefficients, and in terms of the correlations between subject-level intercepts and slopes over time. The relative responsiveness of the WOMAC and COAT total scales was assessed using a multilevel (longitudinal) multivariate (WOMAC, COAT) linear model. Results. The WOMAC and COAT total scales were highly reliable (mean over weeks: WOMAC alpha = 0.98; COAT alpha = 0.97). The correlations between the WOMAC and COAT scales were very high (mean over weeks = 0.92; subject-level intercepts = 0.91, slopes = 0.88). The COAT total scale was significantly more responsive than the WOMAC total scale in the active treatment (34.8% improvement vs 26.8%; p = 0.002). Conclusion. The COAT total scale is simple to administer, reliable, valid, and responsive to treatment effects. (J Rheumatol 2004;31:1180-6) Key Indexing Terms:
COMPREHENSIVE OSTEOARTHRITIS TEST
From the Australian Centre for Complementary Medicine Education and Research, University of Queensland, Brisbane; and Southern Cross University, Lismore, Australia. L.O. Brooks, PhD, Research Methodologist, Australian Centre for Complementary Medicine Education and Research and Southern Cross University; M.I. Rolfe, MStat, Statistician, Southern Cross University; P.A. Cheras, PhD, Deputy Director, Australian Centre for Complementary Medicine Education and Research and University of Queensland; S.P. Myers, PhD, Professor and Director, Australian Centre for Complementary Medicine Education and Research, University of Queensland and Southern Cross University. Address reprints requests to Dr. L. Brooks, Graduate Research College, Southern Cross University, PO Box 157, East Lismore, Australia. E-mail: lbrooks@scu.edu.au Submitted March 19, 2003; revision accepted December 19, 2003.
|