Background/Purpose:

Thrombotic thrombocytopenic purpura (TTP) is an uncommon disease characterized by thrombocytopenia and microangiopathic hemolytic anemia and, in some cases, fever, neurologic and/or renal abnormalities. The mortality rate is high despite appropriate diagnosis and treatment. Presence of TTP in SLE is rare (< 2.5%) and diagnosis can be difficult between this two pathologies; sometimes, this results in delayed/suboptimal treatment with higher mortality. The aim of this study was to identify novel risk factors for TTP in SLE and to address the epidemiological profile in this subset of patients.

Methods:

We performed a retrospective, case-control study which included patients admitted between January 1994 and March 2013. Three different study groups were included as follows: Cases: TTP/SLE (A) and Controls: non-autoimmune TTP (B) and SLE without TTP (C). TTP was diagnosed by the presence of at least microangiopathic hemolytic anemia, thrombocytopenia < 100,000 cells/µl and high LDH levels. Variables that were measured included: demographic variables, SLEDAI score, clinical and laboratorial parameters (complete blood count, hemolytic parameters and serological tests), treatment, length of hospital stay and mortality. Differences between groups were analyzed by Student t test or U Mann-Whitney. Association between variables was assessed by OR (CI 95%). Multivariate analysis was performed by binary logistic regression model. 

Results:

Ninety one  patients were included: 23 in group A, 22 in group B and 46 in group C. Variables that were associated to TTP diagnosis in SLE patients in comparison to non autoimmune TTP were: lymphopenia (≤1000 cells/µl) (OR 11.5, CI 95% 2.82-47.35), severe anemia(≤7g/dl) (OR 4.9, CI 95% 1.03-7.32) and age (≤30 years) (OR 2.87, CI 95% 1.25-6.55), which remained significantly associated after multivariate analysis. Moreover, after comparing SLE patients with and without TTP, the variables that were related to TTP diagnosis included: severe thrombocytopenia (≤50,000 cells/µl) (OR 17.8, CI 95% 4.66-68.08), severe anemia (OR 8.07 CI 95% 2.33-27.9), history of hematological activity (OR 3.25 CI 95% 1.12-9.39), history of persistent thrombocytopenia (OR 3.21 CI 95% 1.002-10.31), positive antiphospholipid antibody profile (OR 3.11 CI 95% 1.083-8.93) and history of thrombosis (OR 1.20, CI 95% 1.048-1.37).  After the multivariate analysis, variables that remained significant were severe anemia (OR 8.9, CI 95% 1.81-43.8) and severe thrombocytopenia (OR 5.71, CI95% 1.5-21.7). Interestingly, we did not find differences in mortality between patients with TTP associated to SLE and non autoimmune TTP.

Conclusion:

Patients with TTP associated with SLE are younger than non-autoimmune TTP. Severe anemia, severe thrombocytopenia and lymphopenia are independent risk factors for TTP in SLE. These findings might lead to early diagnosis and treatment as well as lower mortality.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/novel-risk-factors-for-thrombotic-thrombocytopenic-purpura-in-systemic-lupus-erythematosus-patients/