Researchers found that autoimmune hemolytic anemia (AIHA), including cold agglutinin disease (CAD), is associated with an increased risk of thromboembolic events (TEE). The study was published in the European Journal of Haematology.

In view of these results, the authors proposed that prophylactic anticoagulation therapy be prescribed as soon as a diagnosis of AIHA is made. 

AIHA is mainly classified according to the optimal binding temperature needed for the autoantibodies to react with the red blood cell antigen. If that temperature is 37oC, the autoantibodies are classified as warm; if the temperature is below 30oC, the autoantibodies are considered cold. 

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The literature review conducted by the authors of this study found many studies suggesting an association between AIHA and TEE. For example, a study found that the cause of death was pulmonary embolism for more than half of the AIHA patients who died during the course of the study.

In a study of patients with CAD, 7.2% were reported to suffer from thromboembolic events (compared to 1.9% in healthy controls). The authors therefore wanted to further investigate the incidence of thromboembolic events in AIHA patients. 

The researchers recruited a total of 77 patients for this study who were diagnosed with AIHA based on their medical report or were positive for the Direct Antiglobulin Test with corresponding signs of hemolysis. The patients were then screened for TEE. 

According to the study, the results were as follow: 

  • Out of the 77 participants, 51 (66%) had warm-AIHA, 13 (17%) had cold-AIHA, 5 (7%) had mixed AIHA, and 8 (10%) had atypical AIHA. 
  • Primary and secondary AIHA was diagnosed in 44% and 56% of patients, respectively. 
  • Out of the 77 participants, 20 (26%) suffered from TEE. This incidence rate of TEE among AIHA patients is consistent with existing literature, which reports an incidence rate of around 11% to 27%. 
  • The majority (80%) of these patients suffered from warm-AIHA and 10% from cold-AIHA.

“In summary, the results of this current retrospective study are in accordance with other studies where the risk of a TEE  is increased in patients with the diagnosis of AIHA,” the authors wrote.


Schär DT, Daskalakis M, Mansouri B, Rovo A, Zeerleder S. Thromboembolic complications in autoimmune hemolytic anemia. Eur J Haematol. Published online September 22, 2021. doi:10.1111/ejh.13710