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

Abstract

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.