Objective: To evaluate the association between pain intensity improvement and improvements in functionality and health status in patients with chronic osteoarthritis pain of the hip or knee.
Methods: Data were obtained from a 12-week, randomized, double-blind, placebo-controlled study of tramadol ER 100 mg, 200 mg, 300 mg, or 400 mg once daily. Patients reported pain intensity with a 100-mm visual analog scale (0 = no pain, 100 = extreme pain) and functionality and health status with the disease-specific Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) questionnaire and the generic Short-Form-36 Health Survey (SF-36). Pain intensity improvement from baseline was categorized as < 0%, 0-14%, 15-29%, 30-49%, 50-69%, and >or= 70%, and mean changes in WOMAC and SF-36 scores were determined for patients in each category.
Results: A total of 1011 patients received placebo (n = 205) or tramadol ER 100 mg (n = 202), 200 mg (n = 201), 300 mg (n = 201), or 400 mg (n = 202). The degree of pain intensity improvement was correlated with the degree of improvement in WOMAC and SF-36 scores; as little as 15% reduction of pain intensity was associated with notable improvements in function and health status. Potential limitations included the lack of established thresholds to assess clinically meaningful changes in these outcomes.
Conclusions: Pain intensity improvement is associated with corresponding improvements in function and health status. While large improvements in pain intensity are associated with large improvements in health status and functionality, modest pain reductions are also associated with improvement of certain health status parameters.