Test-retest reliability of patients global assessment, physician global assessment and Womac Index in knee osteoarthritis

Abstract

Introduction: In osteoarthritis pain and physical function are the main outcome measures, and selfreport questionnaires are the preferent assessment method. This is evidence suggesting that self-reports of physical function represents what people experience while performing activities rather than their ability to perform activities. Objective: To study reliability characteristics for global assessments and compared test reliability of both PGA, MDGA vs. WOMAC in knee osteoarthritis. Methods: Patients that were at least 40 years old and had experienced clinical symptoms of OA in the knee at least 3 months before inclusion into study were eligible for inclusion in this trial. All patients were required to fulfill the American College of Rheumatology classification criteria for OA in the knee. The Patient Global Assessment (PGA) asked a patient to rate on the scale how they feel overall. The Physician Global Assessment (MDGA) is a similar item completed by the assessing physician. Both these measures were incorporated into other indices. To assess patient pain we used the Western Ontario and McMaster Universities Index; The WOMAC contains five pain, two stiffness, and 17 physical function items, and is available in five-point Likert (LK) and 100-mm visual analogue (VA). Results: We examined 53 patients with OA of 50 years old. Patients completed the PGA, visual analog scale for pain (VAS Pain), VAS Fatigue, VAS Sleep and PGA. Physicians completed the MDGA at the time of the patients appointment day. Test results were assessed using interclass correlations (ICC). “Substantial” reliability was between 0.69-0.79 and “almost perfect” > 0.80. As endpoint, physical function and the patient’s global assessment were evaluated at baseline and at the 8 week. The Western Ontario and McMaster Universities (WOMAC) Osteoarthritis Index was used to assess physical function and pain. This study was conducted according to the principles of the Declaration of Helsinki (1996) and good clinical practice. In the study participated three rheumatologists and 53 patients. Test reliability was 0.702 for PGA, 0.961 for MDGA, and 0.897 for WOMAC; VAS results were 0.742 for Pain, 0.741 for Fatigue, and 0.800 for Sleep. The correlation between PGA and MDGA was -0.172. The WOMAC measured pain in 50%, stiffness in 42.7% and physical function in 53.9%. Conclusion: The patients with osteoarthritis had relatively low physical function and knee pain. The Patient Global Assessment, Physician Global Assessment, WOMAC index, and VAS Pain, VAS Fatigue, and VAS Sleep all showed good to excellent test-retest reliability in OA after hospitalization. MDGA was more reliable than PGA. The correlation between PGA and MDGA was low.