OBJECTIVES: SLE is an autoimmune disease with a broad list of differential manifestations, further complicating its diagnosis. The objective of this study was to compare clinical outcomes, resource utilization and costs between patients with earlier versus later SLE diagnosis. METHODS: Patients aged 18-64 years and at least 2 years of continuous coverage were identified from a large claims database between January 2000 and June 2010.  Confirmed SLE diagnosis required > 1 claim for rheumatologist visits with a diagnostic code for SLE (ICD-9 code:710.0x) and, in some cases, an additional requirement for ≥ 1 claim for a typical SLE medication.  All patients had ≥ 12 months of continuous baseline eligibility prior to SLE diagnosis. SLE probable onset date was identified during the baseline period by the 2nd claim for antinuclear antibody tests or prodromal symptoms of SLE.  Patients were stratified into Early or Late Diagnosis groups based on time between probable SLE onset and diagnosis (<6 or ≥6 months, respectively).  Patients in each group were propensity-score matched on age, gender, diagnosis year, region, and health plan type. Resource use and costs were compared post-diagnosis between groups using Poisson regression.   Per-patient-per-month costs (PMPM) were calculated to account for differential lengths of SLE periods between groups. RESULTS: There were 4274 matched patients per group. Post-SLE diagnosis, the Early Diagnosis group had lower rates of non-severe (RR=0.95; 95% CI 0.94-0.96) and severe flares (RR=0.83; 95% CI 0.78-0.89)) and hospitalizations (RR=0.72 (95% CI 0.68-0.77)) compared to the Late Diagnosis group. Mean inpatient costs were lower for the Early Diagnosis ($411 PMPM) patients compared to Late Diagnosis patients ($539 PMPM, P-value=0.001).  Results were consistent for other cost categories.    CONCLUSIONS: Patients diagnosed with SLE sooner may experience lower flare rates, less health care utilization and lower costs. This finding needs to be further explored within the context of background SLE disease activity.