Objective: To estimate the prevalence of rheumatoid arthritis (RA) in Puerto Rico, to describe disease-modifying antirheumatic drug (DMARD) dispensing patterns by prescriber specialty, and to illustrate the impact of RA case definition on the estimated prevalence. Methods: This study estimated the prevalence of RA in Puerto Rico during 2016 among Medicaid and Medicaid–Medicare dually eligible beneficiaries of the Mi Salud health care plan, a federally funded health insurance program. DMARD dispensing and cost patterns were described and stratified by provider specialty. A sensitivity analysis was conducted to evaluate the effect of RA case definition on estimated prevalence. Results: The prevalence of RA in 2016 was estimated to be 2 cases per 1,000 beneficiaries, with 3 per 1,000 beneficiaries among females, 4.5 times that of males. In total, 44% of beneficiaries received conventional synthetic DMARDs (csDMARDs) only, 32% received biologic or targeted synthetic DMARDs (b/tsDMARDs) only, and 24% received a combination of csDMARDs and b/tsDMARDs. Rheumatologists and a combination of specialties accounted for the highest median number of dispensed DMARDs, with 14 each. A sensitivity analysis revealed that when RA cases with ≥3 medical claims were restricted to having ≥1 DMARD claim, the estimated prevalence changed from 6 to 3 cases per 1,000 beneficiaries. Conclusion: The prevalence of RA in Puerto Rico in this study is lower than reported in the mainland US, possibly due to more stringent criteria to define RA. DMARD dispensing and cost patterns are similar to those found in other studies. Claims algorithms that identify RA have higher validity when pharmacy data is included.
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