(015) Estimating Prevalence of Moderate-to-Severe Systemic Lupus Erythematosus. A Literature Review

Background: Systemic Lupus Erythematosus (SLE) is a heterogenous chronic autoimmune disease of unknown cause, with severity ranging from mild to severe. The overall global prevalence of SLE is estimated at around 44 per 100,000 persons but the prevalence of moderate-to-severe SLE remains uncertain

Objectives: To estimate the prevalence of moderate-to-severe SLE

Methods: A literature search was performed in PubMed and Embase covering the last 10 years up until April 2023. Eligibility criteria included observational studies with samples ≥100 moderate-to-severe SLE patients and reporting prevalence or allowing the prevalence to be calculated for moderate SLE, severe SLE or moderate-to-severe SLE together as described by the authors or, if not stated, defined as SLEDAI (SLE Disease Activity Index) ≥6. Juvenile SLE, lupus nephritis and neuropsychiatric SLE populations were excluded. A random-effect model with a DerSimonian-Laird tau2 estimator was used to generate pooled estimates and heterogeneity identified using the I2 statistic

Results: 28 publications were included (35.7% from North America, 32.1% from Asia, 21.4% from Europe, 7.1% from Oceania and 3.6% from South America). No studies reported prevalence of moderate-to-severe SLE within the general population. The pooled prevalence of moderate SLE among all SLE was 44% (95% confidence interval; 35-53%) (n=15 publications), for severe SLE (16 publications) 27% (20-33%), and in those that studied moderate-to-severe SLE together (10 publications) 43% (26-61%). Regional variations showed the highest prevalence in South America (43% [0-100%]) and Asia (40% [25-55%]), followed by Oceania (39% [29-48%]), North America (37% [30-44%]), and Europe (30% [19-41%]). There was significant heterogeneity across publications (I2=100%). 15 publications (53.6%) used an algorithm in administrative data to define severity, of which 10 (66.7%) used an algorithm defined by Garris et al. in 2013, which combines diagnosis codes for SLE, SLE-related conditions, and medications. The remaining 13 publications used the disease activity indexes SLEDAI or BILAG (British Isles Lupus Assessment Group Index) to assess severity with different score thresholds. Prevalence estimates of moderate-to-severe SLE were higher in studies that used an algorithm in administrative data (40% [32-47%]), compared to studies using a disease activity index (33% [24-41%]) (I2=100%)

Conclusions: There is an absence of studies reporting absolute prevalence of moderate-to-severe SLE and the estimation among all SLE continues to represent a challenge due to heterogeneity in the measures of severity and score thresholds used. Further studies and efforts are needed to reach a consensus on its definition and harmonise its use in research/clinical practice