Background/Purpose: Thrombosis in patients with Systemic Lupus Erythematosus (SLE) is a major cause of morbidity, it occurs in 9-37%, at younger age, and it represents 27% of mortality. Lupus anticoagulant (LA) is strongly associated with thrombosis; however, most events occur in patients who are negative for LA. The aim of our study was to determine the baseline characteristics associated with thrombosis in an inception cohort of SLE patients and in the subset of patients without LA.  

Methods: A longitudinal inception cohort of 223 SLE patients (less than 12 months of accrual ≥4 criteria), predominantly female (90%), mean age 27.2 years at diagnosis, was studied. Baseline evaluation included medical history, physical exam, clinical variables, SLE characteristics, SLE activity (SLEDAI-2K), modified damage index (SLICC/DI), autoantibodies, laboratory tests, homocystein and high-sensitivity C-reactive protein (hs-CRP). Thrombotic events were diagnosed on clinical manifestations and confirmed by appropriate studies. Statistical analyses: Descriptive statistics, Student T-test, Mann-Whitney U-test, Chi-square, Fisher exact test, Logistic Regression. P <0.05 

Results: During 1269 patient-years of follow-up, thrombosis occurred in 35 patients (16%), incidence rate 25.6 per 1000 patient-years. Most of the events (57%) occurred at onset or during the first year of diagnosis of SLE. At baseline, patients with thrombosis had lower body mass index (BMI) (p=0.03), smoking (p=0.02), vascular insufficiency (p=0.05), immobilization (p<0.0001), recent surgery (p=0.004), anti-RNP (p=0.04), lupus anticoagulant (LA) (p=0.006), and higher modified SLICC/DI (p=0.03). Since only 8/35 thromboses were associated to LA, we identified those variables associated with thromboses in patients with LA negative: smoking (p=0.004), vascular insufficiency (p=0.03), immobilization (p<0.0001), serositis (p=0.04), and hs-CRP (p=0.02). In the multivariate analysis, BMI (OR 0.79 95% CI 0.65-0.95, p=0.016), anti-RNP (OR 1.02 95%CI 1.00-1.03, p=0.003) and LA+ (OR 8.05 95% CI 1.75-36.88, p=0.007) were independent risk factors for thrombosis in the general cohort. After excluding patients with LA, smoking (OR 6.1, 95% CI 1.7-21.8 p=0.006), vascular insufficiency (OR 28.7 95% CI 2.4-342.9, p=0.008), and immobilization (OR 31.3 95%CI 2.6-381.4, p=0.007) were independent risk factors for thrombosis. 

Conclusion: Patients with SLE are at an increased risk of thrombosis, particularly during the first year of diagnosis. Although LA is a strong risk factor, most thrombotic events occur in patients without LA; in this subset, smoking, immobilization and vascular insufficiency are the most important. All of them are potentially modifiable.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/clinical-variables-associated-with-thrombosis-at-systemic-lupus-erythematosus-diagnosis-differences-between-patients-with-positivenegative-lupus-anticoagulant/