A longitudinal analysis of costs associated with change in disease activity in systemic lupus erythematosus

Objectives: To estimate the economic consequences of changes in disease activity on healthcare resource utilization (HRU) and costs. Methods: A retrospective longitudinal study of systemic lupus erythematosus (SLE) patients receiving care in a regional integrated health delivery system in the US from 01/2004 through 03/2011 was conducted using electronic health records, medical chart reviews, and claims. Eligible patients were 18 years old, with 1 rheumatologist-confirmed SLE diagnosis and 1 eligible rheumatology encounter. Patients were continuously enrolled 90 days before and 30 days after the encounters. Charts were manually reviewed to estimate SLEDAI scores. Average unit costs of each medical procedure, facility use, and prescription were estimated from a payer perspective (2011 USD) using a managed care claims database. HRU and costs were calculated for the 30-day period surrounding every SLEDAI score date (10 days before and 19 after). Relationships between HRU/costs and SLEDAI scores were estimated using mixed-effect models. Results: Overall, 178 SLE patients were included; mean age was 50.6 years, 91% were female, and 95.5% Caucasian. Patients had a total of 1343 encounters with SLEDAI scores over an average period of 1035 days. Reductions of SLEDAI scores were associated with reductions in HRU and costs. SLEDAI score reductions of 4-points were associated with reductions of 10% HRU and 14% costs over a 30-day period; reductions of 8-points had associated reductions of 19% HRU and 26% costs; and reductions of 10-points had associated reductions of 23% HRU and 31% costs. Annualized, changes in SLEDAI scores are associated with changes of $2485 (SLEDAI score change: 10-6), $4624 (10-2), and $5579 (10-0), respectively. Conclusion: Reductions in disease activity were associated with substantial reductions of HRU and costs. Limitations: Only short-term effects of disease activity change were investigated, disregarding other potential benefits of low disease activity on long-term organ damage prevention or comorbidities.