Venous thromboembolic events during warm autoimmune hemolytic anemia

Thrombotic manifestations are a hallmark of many auto-immune diseases (AID), specially of warm autoimmune hemolytic anemia (wAIHA), as 15 to 33% of adults with wAIHA experience venous thromboembolic events (VTE). However, beyond the presence of positive antiphospholipid antibodies and splenectomy, risk factors for developing a VTE during wAIHA have not been clearly identified. The aim of this retrospective study was to characterize VTEs during wAIHA and to identify risk factors for VTE. Forty-eight patients with wAIHA were included, among whom 26 (54%) had secondary wAIHA. Eleven (23%) patients presented at least one VTE, that occurred during an active phase of the disease for 10/11 patients (90%). The frequency of VTE was not different between primary and secondary AIHA (23.7 vs. 19.2%; p = 0.5). The Padua prediction score based on traditional risk factors was not different between patients with and without VTE. On multivariate analysis, total bilirubin ≥ 40 μmol/L [odds ratio (OR) = 7.4; p = 0.02] and leucocyte count above 7x10(9)/L (OR = 15.7; p = 0.02) were significantly associated with a higher risk of thrombosis. Antiphospholipid antibodies were screened in 9 out the 11 patients who presented a VTE and were negative. Thus, the frequency of VTE is high (23%) during wAIHA and VTE preferentially occur within the first weeks of diagnosis. As no clinically relevant predictive factors of VTE could be identified, the systematic use of a prophylactic anticoagulation should be recommended in case of active hemolysis and its maintenance after hospital discharge should be considered. The benefit of a systematic screening for VTE and its procedure remain to be determined.