FACTORS ASSOCIATED WITH THE CHOICE OF BIOLOGIC DISEASE MODIFYING ANTI-RHEUMATIC DRUGS AMONG RHEUMATOID ARTHRITIS PATIENTS IN CALIFORNIA MEDICAID

Purpose: The objective of this study was to identify sociodemographic and Medicaid plan factors associated with the use of biologic disease-modifying anti-rheumatic drugs (DMARD) over standard DMARDs among patients with rheumatoid arthritis (RA) in California Medicaid (Medi-Cal).

Method: Patient-level data for 7259 DMARD recipients aged between 18 to 100 years old with at least one diagnosis of RA (714.XX) and one DMARD use, was constructed using California Medicaid paid insurance claims and eligibility files, between 01/01/1998 to 12/31/2005. The outcome of interest was the choice between standard DMARDs (methotrexate, lefluonomide, hydroxychloroquine and sulfasalazine) and biologic DMARDs (adalimumab, etanercept, anakinra and infliximab). Biologic DMARDs could have been used in combination with standard DMARDs. Chi-square test and logistic regression model were applied to examine the association between the choice of DMARD and sociodemographic factors (age, gender, race and county residency), RA related medical utilization in the past six months, and Medi-Cal plan factors (exclusive fee-for-service reimbursement in beneficiary’s county, and Medicare and Medicaid dual eligibility).

Result: The mean age was 57.8 (±14.8) years with a majority of females (79.8%) and Caucasians (34.8%). Around 14% percent of patients were taking biologic DMARDs. Chi-squared test results showed that age, gender, race, county of residence, dual eligibility, and having recent RA related medical utilization were significantly associated with the choice of biologic DMARD. After adjustment of 13 different comorbidities in the logistic regression model,  the results indicated that the youngest age group (18-34 years old) had the highest odds ratio (OR) of using biologic DMARDs (OR=2.46, CI: 1.82 to 3.32), compared with the age group over 65 years of age, and the OR decreased consistently as age increased. As compared to Caucasians, African American had the lowest OR (0.52, CI: 0.40 to 0.67). The OR of dual eligibility was 1.70 (CI: 1.44 to 2.02). Having RA related medical utilization in the past 6 months had OR=2.89 (CI: 2.49 to 3.45). Patients residing in counties from northern California had OR=0.75 (CI: 0.63 to 0.89) as compared to those in southern California.

Conclusion: In this Medicaid population, we found marked evidence of socio-demographic disparity in DMARD treatment for RA. Our results also highlight the variation in DMARD utilization based on geographic location, and type of insurance coverage.