Objective: Assess healthcare costs associated with systemic lupus erythematosus (SLE) flares among patients with and without lupus nephritis (LN).

Methods: This retrospective cohort study used medical and pharmacy claims data from the United States-based Optum Clinformatics database to identify adults with SLE between 1 January 2016, and 31 December 2018. Index was the date of a patient’s earliest SLE diagnosis claim during the identification period. Patients were categorized based on ICD-9/-10 diagnosis codes into one of two cohorts: SLE with LN (LN) and SLE without LN (non-LN). Baseline characteristics were assessed in the 12 months preceding index (baseline period). The presence, severity, and healthcare costs (in 2019 US dollars) of flares were determined in the 12 months following index (follow-up period).

Results: Overall, 11,663 patients with SLE were included (LN, n = 2916; non-LN, n = 8747). During the baseline period, a greater proportion of patients in the LN cohort versus non-LN cohort had a Charlson Comorbidity Index score ≥4 (72.5% vs 13.7%) and inpatient stays (41.0% vs 17.0%). A total of 12,190 flares were identified during the follow-up period (LN, 3494; non-LN, 8696). A greater proportion of flares experienced by patients with LN versus those without LN were moderate (61.2% vs 53.6%) and severe (10.6% vs 5.4%). The mean (standard deviation [SD]) number of moderate and severe flares per patient was greater among the LN cohort than the non-LN cohort (moderate: LN, 1.8 [1.2] and non-LN, 1.4 [1.2]; severe: LN, 0.2 [0.6] and non-LN, 0.1 [0.3]). The mean (SD) total healthcare costs associated with SLE flares of any severity were greater for patients with LN (LN, $5842 [9604]; non-LN, $2600 [4249]). The mean (SD) cost per flare increased with severity (mild: LN, $2753 [4640] and non-LN, $1606 [2710]; moderate: LN, $4561 [7156] and non-LN, $2587 [3720]; severe: LN, $29,148 [27,273] and non-LN, $14,829 [19,533]).

Conclusions: Patients with SLE with LN have greater healthcare costs than those without LN. Flares among patients with LN were more frequent, severe, and costly than among patients without LN. This highlights the need for treatments that prevent or reduce flares among patients with SLE, both with and without LN.