Lymphopenia as a risk factor for neurologic involvement and organ damage accrual in patients with systemic lupus erythematosus: A multi-center observational study.

Objective: Detailed analysis of hematological manifestations (HM) in systemic lupus erythematosus (SLE) are limited and their clinical impact on disease remain obscure. Here, we aimed to decipher factors associated with different hematological abnormalities in SLE patients and to assess their impact on disease related outcomes.

Methods: A dataset (GIPT) originating from SLE patients of six European tertiary centers was assessed. Six-monthly visits of each patient for at least 2 years were registered. The association between hematologic manifestations (HM; per ACR-1997criteria) and clinical/serologic variables, as well as the impact of HM on disease related outcomes (damage, infection and hemorrhage) were explored. Scores on the Systemic Lupus Erythematosus Disease Activity Index 2000(SLEDAI2K), the Systemic Lupus International Collaborating Clinics (SLICC)/American College of Rheumatology (ACR) Damage Index (SDI) and events for any infection and hemorrhage were recorded. Results were compared with a cross-sectional, well-characterized SLE dataset from Sweden. Descriptive statistics, the generalized estimating equations (GEE), general linear models (GLM), Cox regression models were applied.

Results: We monitored 1425 longitudinal visits in 286 SLE patients with HM (GIPT dataset: 88% female, 95% Caucasian, 68% dsDNA positive). Thrombocytopenia (regression coefficient [95% confidence interval] 1.86[1.1-3.13]) and neurologic involvement (ACR-8) (2.1[1.10-3.89]) were associated with lymphopenia (<1000/mm); the latter was an independent predictor of organ damage accrual (1.68[1.2-2.62]). These associations were confirmed in an independent dataset of 1348 SLE patients (86% female, 93% Caucasian, 61% dsDNA positive) in Sweden.Severe lymphopenia (<500/mm) and severe thrombocytopenia (<20 K/mm) were associated with increased risk for infection (hazard ratio [95% confidence interval] 2.56[1.23-5.31]) and hemorrhage (4.38[2.10-11.1]), respectively, independent of the effect of other predictors.

Conclusion: Lymphopenia in SLE is independently associated with neurologic involvement and organ damage accrual, and thus, may be considered as a marker of severe/progressive disease.