Prediction of thrombotic events in patients with autoimmune hemolytic anemia: a multicenter retrospective observational study.

Background: Autoimmune hemolytic anemia (AIHA) is recognized to increase the risk of thrombotic events (TE), including venous thromboembolism (VTE) and arterial thromboembolism (ATE), but little is known about specific risk factors and characteristics.

Methods: This retrospective multicenter observational study, sought to assess TE incidence, identify associated thrombotic risk factors and assess the external validity of the Padua score in AIHA for predicting VTE.

Results: TE incidence during the study period was 25% (CI95%: 17-36), consisting of 19 VTE in 16 patients (18% [CI95%: 9-28]) and 11 ATE in 7 (8% [CI95%: 4-16]). A high number (≥ 5) of hemolysis attacks was associated with overall TE (OR 6.9 [CI95%: 1-82], p = 0.03). Univariate analysis confirmed splenectomy and VTE history as the strongest VTE-related risk factors (OR 7.5 [CI95%: 1-44], p = 0.009 and OR 3.8 [CI95%: 1-14], p = 0.04), whereas having primary warm AIHA was identified as a novel risk factor (3.1 [1-11] p = 0.05) which needs to be confirmed in further studies. ATE risk factors were age≥ 80 years at diagnosis (OR 8.9 [CI95%: 1-68] p = 0.02), and having ≥ 3 cardiovascular risk factors (OR 8.9 [CI95%: 1-70] p = 0.01). The area under the Receiver Operating Characteristic curve of the Padua score was 0.66.

Conclusions: TE incidence is high in AIHA, especially when there are repeated hemolysis attacks and associated VTE and/or ATE-related risk factors, thus warranting the conduct of prospective clinical trials to allow for an improved TE risk stratification and to design adapted management for both VTE and ATE.