An observational study of the discharge records of more than 14,000 patients with colorectal cancer who underwent colorectal resection showed that women who had a perioperative allogeneic transfusion (transfusion of blood products from another person) were more likely than men to incur a venous thromboembolism (VTE). The records for recipients of autologous transfusions were not examined. Allogeneic transfusion in this study cohort also increased the length of hospital stay, the likelihood of ICU admission, the likelihood of death, and overall hospital charges.

Allogeneic transfusions can confer important-even lifesaving-benefits, but they pose risks as well: derangement of the coagulation cascade, changes in the inflammatory response, and transmission of infectious agents. Studies have shown that a patient's sex may play a role in the formation of thrombi. The authors, citing other research, wrote that, "Estrogens have been shown to alter the production of coagulation factors from the liver, accounting, in part, for the increased risk of VTE and myocardial infarction in women receiving hormone therapy."

The researchers pointed out several study weaknesses. One was their inability to determine the temporal relationship between the VTE and the transfusion by reviewing discharge data, which provided less information than reviewing medical records would have. But the large number of records examined and the tightly focused study factors (the presence of VTE, the type of transfusion, and the fact that all patients underwent the same surgical procedure) they noted as study strengths. And because the study didn't seek a sex-specific link between allogeneic transfusion and VTE, the authors called for additional study.-TS