Efficacy of Prolonged Anticoagulation for Primary Prevention of Venous Thromboembolic Disease in Autoimmune Hemolytic Anemia: a Prospective, Phase II, Randomized, Multicenter Study

Autoimmune hemolytic anemia (AIHA) is a rare autoimmune disease (incidence \<1/100,000 population) responsible for the destruction of red blood cells by the host immune system, notably through the action of autoantibodies. Apart from complications related to anemia, the occurrence of venous thromboembolism (VTE) in this population is frequent, estimated at 20-27%. The risk of VTE is highest during the period of hemolysis, especially during the first 3 months after the diagnosis of AIHA. This risk is 7.5 \[4.7; 12.0\] times greater than in the general population. No clinical predictive factor for VTE was identified and the usual factors (cancer, previous VTE, bed rest \>3 days, surgery, age \>70 years, heart or respiratory failure, myocardial infarction, stroke, obesity, hormone replacement therapy) were not considered. Several biological risk factors have been suggested (depth of anemia, bilirubin level, leukocyte count, antiphospholipid antibodies) but have not been confirmed in other studies. AIHA is therefore a risk factor for VTE in its own right, and the National Diagnostic and Care Protocol (NDCP) recommends the implementation of VTE prevention during acute hemolysis (Grade C). However, the value of this prophylaxis has never been prospectively evaluated and its duration is empirical. In practice, low-molecular-weight heparin (LMWH) is generally used during "flare-ups" of AIHA (diagnosis and relapse) in hospitalized patients, but is rarely continued beyond the hospital phase when VTE also occurs in ambulatory patients. Thus, we hypothesize that prolonged preventive anticoagulation during the 12-week risk period following diagnosis or relapse of AIHA could decrease the incidence of VTE. In orthopedic surgery, this strategy has been proven to decrease VTE from 50% to 10-15%. In certain high-risk medical situations, prolonged prophylaxis with apixaban has been shown to decrease the occurrence of VTE from 10.2% to 4.2% in solid cancers4 and from 4-11% to 2% in myeloma.