Health care costs in US patients with and without a diagnosis of osteoarthritis

BACKGROUND: Osteoarthritis is a chronic and costly condition affecting 14% of adults in the US, and has a significant impact on patient quality of life. This retrospective cohort study compared direct health care utilization and costs between patients with osteoarthritis and a matched control group without osteoarthritis. METHODS: MarketScan(®) databases were used to identify adult patients with an osteoarthritis claim (ICD-9-CM, 715.xx) in 2007, and the date of first diagnosis served as the index. Patients were excluded if they did not have 12 months of continuous health care benefit prior to and following the index date, were aged <18 years, or lacked a second diagnosis code for osteoarthritis between 15 and 365 days pre-index or post-index. Osteoarthritis patients were matched 1:1 to patients without osteoarthritis for age group, gender, geographic region, health plan type, and Medicare eligibility. Multivariate analyses were conducted to assess for differences in utilization and costs, controlling for differences between cohorts. RESULTS: The study sample included 258,237 patients with osteoarthritis and 258,237 matched controls without osteoarthritis. Most patients were women and over 55 years of age. Patients with osteoarthritis had significantly higher pre-index rates of comorbidity than controls. Mean total adjusted direct costs for osteoarthritis patients were more than double those for the control group at US$18,435 (95% confidence interval [CI]: US$18,318–US$18,560) versus US$7494 (95% CI: US$7425–US$7557). Osteoarthritis patients incurred significantly higher inpatient costs at US$6668 (95% CI: US$6587–US$6744) versus US$1756 (95% CI: US$1717–US$1794), outpatient costs at US$7840 (95% CI: US$7786–US$7902) versus US$3675 (95% CI: US$3637–US$3711), and prescription drug costs at US$3213 (95% CI: US$3195–US$3233) versus US$2245 (95% CI: US$2229–US$2262) compared with the controls. CONCLUSION: The direct health care costs of osteoarthritis patients were over two times higher than those of similar patients without the condition. The primary drivers of the cost difference were comorbidities and inpatient costs.