Eligibility, utilization, and costs in a California Medicaid lupus population.

Objective: To investigate whether ethnicity was associated with differences in Medicaid eligibility, health care utilization, and direct medical costs in a systemic lupus erythematosus (SLE) population.

Methods: A retrospective analysis of California Medicaid claims data was conducted on patients with SLE. Patient eligibility and month-by-month utilization and costs were computed and compared across ethnic groups. Descriptive statistics are presented. A mixed regression model on patient-level data was used to verify the trends of the aggregate data, controlling for covariates. A survival regression model on time to ineligibility was used to show eligibility patterns adjusted for covariates.

Results: Hispanic patients were less likely to have a lengthy eligibility period as compared with other cohorts (approximately 50% versus 70% eligible at month 36, respectively). As treatment progressed, Hispanics generated lower total costs than other cohorts. Results for inpatient frequency, prescription costs, and outpatient/physician/supply (Part B) costs followed similar patterns. Mixed regression model findings revealed that when adjusted for age, sex, and aid program, total costs for Hispanic patients decreased as the length of care increased, in contrast to other ethnic groups. The interaction between ethnicity and treatment progression measured by quarter was significant (P <0.0001), but ethnicity as a main effect was not (P=0.091). This suggests that differences in total costs are small initially, but as the followup period extends, Hispanic patients experience lower total costs as compared with other ethnic groups.

Conclusion: These California Medicaid program data reinforce the importance of investigating treatment differences in ethnic groups with SLE.