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Patient Preference in a Crossover Clinical Trial of Patients with Osteoarthritis of the Knee or Hip: Face Validity of Self-Report Questionnaire Ratings
THEODORE PINCUS, XIAOFEI WANG, CECILIA CHUNG, TUULIKKI SOKKA, and GARY G. KOCH
ABSTRACT. Objective. To analyze correlational validity of self-report responses regarding patient preference between 2 drugs at the conclusion of a crossover double-blind clinical trial in patients with osteoarthritis (OA) of the knee or hip. Methods. Patients were randomized to 6 weeks' treatment of diclofenac/misoprostol or acetaminophen, followed by crossover to 6 weeks of the other drug. Patient preference was queried at the final visit: "Please compare control of your arthritis during the first and second periods as 'much better' or 'better' in the first period, 'no different' or 'better' or 'much better' in the second period." Patient preference ratings were evaluated in comparisons with 4 independent self-report measures within each treatment period: (1) change in Western Ontario McMaster (WOMAC) questionnaire scores; (2) change in pain visual analog scale (VAS) on a multidimensional Health Assessment Questionnaire (MDHAQ); (3) patient ratings of drug efficacy; and (4) patient report of change in arthritis status, as well as investigator ratings of the more efficacious drug. Results. Among 173 patients, diclofenac/misoprostol was rated as "much better" by 54 and "better" by 45, acetaminophen was rated as "better" by 18 and "much better" by 17, and "no difference" by 39 patients. Spearman rank correlations for patient preferences were significant for changes in WOMAC scores, pain VAS, and independent patient ratings of drug efficacy and changes in arthritis status within each treatment period, as well as with physician ratings of the more efficacious drug (p < 0.001). Conclusion. Significant correlational validity is documented for patient self-report of preferences between 2 drugs compared to independent measures within each treatment period in this crossover clinical trial in patients with OA of the knee or hip. (J Rheumatol 2005;32:533-9) Key Indexing Terms:
OSTEOARTHRITIS
From the Division of Rheumatology and Immunology, Vanderbilt University School of Medicine, Nashville, Tennessee; and the University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA. Supported in part by Pfizer, the Arthritis Foundation, Centocor Health Outcomes in Rheumatic Diseases (CHORD) fellowship program, and the Jack C. Massey Foundation. T. Pincus, MD; C. Chung, MD; T. Sokka, MD, PhD, Division of Rheumatology and Immunology, Vanderbilt University School of Medicine; X.F. Wang, PhD, Department of Biostatistics and Bioinformatics, Duke University; G.G. Koch, PhD, Department of Biostatistics, University of North Carolina at Chapel Hill. Address reprint requests to Dr. T. Pincus, Division of Rheumatology and Immunology, Vanderbilt University School of Medicine, 203 Oxford House, Box 5, Nashville, TN 37232-4500. E-mail: t.pincus@vanderbilt.edu Submitted April 26, 2004; revision accepted September 20, 2004. |