OBJECTIVES: Standard sources of healthcare resource utilization(HCRU) for systematic lupus erythematosus (SLE) patients lack granular clinical information and longitudinal follow-up. Due to the heterogeneous nature of SLE, in which disease activity fluctuates with time and acute events such as flares and remissions are common, little is known about the relationship between disease activity and HCRU.

METHODS: We combined data from the longstanding Johns Hopkins Lupus Cohort, where SLE Disease Activity Index (SLEDAI) was collected at a minimum every six months during standardized protocol visits, with health system cost data (Casemix). Patient resource utilization and registry data were included each calendar half-year where at least 1-registry visit and one Casemix item was observed. We computed the annual HCRU and cost of care by type of utilization: outpatient(OP), inpatient(IP), emergency room (ER) and pharmaceutical(Rx). We described the impact of disease activity (based on the worst SLEDAI score observed in each period) on utilization and costs using mixed effect generalized linear models where categorized SLEDAI score 0 (no activity), 1-5 (mild), 6-10 (moderate), 11+ (high) is used as a predictor of outcomes, adjusted for patients fixed effects and disease characteristics.

RESULTS: 1,111 patients contributing 5,094 patient years between 2013-2019 were included in our analysis. The average annual cost of care (and SD) by type was $5,337(12,997), $3,896(25,297), $215(1,062), $3,251(7,721) for OP, IP, ER and Rx. Regressions showed that total costs in the 6-month period was 14% higher for mild, 32% higher for moderate and 76% higher for severe relative to SLEDAI score of 0 (no activity), (all p<0.001).

CONCLUSIONS: Using detailed clinical data collected via registry, combined with comprehensive utilization and costs, we have described the relationship between disease activity and HCRU over time. These estimates explain the clinical burden of the disease and can inform cost estimates in future studies of treatments that impact SLEDAI score.