Determinants of major direct medical cost categories among patients with osteoporosis, osteoarthritis, back pain or fibromyalgia undergoing outpatient rehabilitation.

OBJECTIVE To identify determinants of direct medical costs among patients with osteoporosis, osteoarthritis, back pain or fibromyalgia. DESIGN Cross-sectional study. PARTICIPANTS Convenience sample of 410 patients undergoing outpatient rehabilitation. METHODS Resource use was assessed with a self-report retrospective questionnaire, and direct medical costs were calculated considering outpatient physician services, non-physician health services, medication and inpatient treatment. Non-parametric bootstrap techniques with 1,000 replications were used to estimate means of costs and their 95% confidence intervals (CI). To identify determinants of costs, a generalized linear model with log link function and gamma distribution, as well as a multivariate logistic regression analysis, were performed. RESULTS Medical indication (p < 0.001), age (p = 0.034) and the scales of the Short Form-36 (SF-36) role physical (p < 0.001), physical functioning (p = 0.036), social functioning (p = 0.047) and vitality (p = 0.005) were significant predictors of direct medical costs, whereas the medical indication fibromyalgia (odds ratio (OR) = 5.74, 95% CI 2.051-16.066, p = 0.001), the Short-Form 36 (SF-36) scale role physical (OR = 0.988, 95% CI 0.980-0.996, p = 0.002) and comorbidity (OR = 1.161, 95% CI 1.043-1.292, p = 0.006) were statistically significant determinants of high direct medical costs beyond the median. CONCLUSION Our work confirms known predictors of direct medical costs and broadens the understanding of determinants of direct medical costs beyond the median.