Background/Purpose:  Prevalence estimates of Systemic Lupus Erythematosus (SLE) in the U.S. vary, with numbers ranging from 161,000 (Helmick, 2008) to 1.5 million (Lupus Foundation of America). Renal involvement (Lupus Nephritis; LN), the most common serious manifestation of SLE is reported to develop in up to two-thirds of patients cared for in specialty centers. In the absence of population-based data, it is difficult to estimate the burden of SLE and LN in the US population. 

Objective: To estimate the prevalence of SLE and LN among commercially insured and Medicare and Medicaid enrolled populations in the US

Methods: Subjects with at least 12 months of continuous enrollment were selected from the following administrative databases: Truven MarketScan^® Commercial Claims & Encounters Data (n=30,912,744), Truven MarketScan^® Medicaid Multi-State data (n=3,979,342) and Centers for Medicare and Medicaid Services Medicare data (n=46,520,716). SLE cases were defined as minimum of 3 claims (ICD-9-CM 710.0) occurring within 2009. LN cases were defined using Chibnik, 2010 requiring at least 2 visits to the nephrologists or at least 2 LN diagnoses (ICD-9-CM codes 580-586, 791.0) within 12 months from SLE index date. Sensitivity analyses were conducted by varying the ascertainment criteria for SLE and LN. Overall and age, gender- specific SLE and LN prevalence rates per 100,000 were computed. An estimate of the total number of SLE and LN patients was projected by applying these prevalence rates to the 2009 U.S. population (~306 million).

Results: The overall prevalence of SLE was 81, 106 and 144 per 100,000 in the Commercial, Medicaid and Medicare databases respectively; leading to a projection of 313,436 SLE patients in US population. The prevalence of LN was 15, 31 and 40 per 100,000, in the three databases respectively; leading to a projection of 63,256 LN patients. The age-specific prevalence of SLE and LN were highest between ages of 18 and 64 years (112 and 22 per 100,000, respectively) compared to children (7 and 3 per 100, 000) and those over 65 (102 and 22 per 100,000). SLE and LN prevalence was greater in females (227 and 52 per 100,000, respectively) as compared to males (30 and 10 per 100,000), consistent with previous reports. Although only 15.1% of all US citizens were insured by Medicare as of 2009, 26.2% of all SLE patients were on Medicare; the majority of the latter (51.5%) were under 65, indicating the impact of disability in this disease.

Conclusion: Based on an analysis of billing records from 81 million subjects, the disease burden of SLE and LN in the US is estimated at 313,436 (100 per 100,000) and 63,256 (20 per 100,000) respectively. The estimate for SLE is consistent with the conservative published estimates, and reflects the stringent case definition applied. This proportion of SLE with LN (20%) is significantly lower that reported in cohort studies, suggesting that cohorts incorporate a more severe subset of the population identified by the present algorithms.  Both SLE and LN were more frequent in the publically insured population, with highest rates among Medicaid subjects less than 65 years of age, consistent with the high risk of disability associated with this disease.