Red Cells and Cancer II: Blood Donation and Cancer Risk
Abstract & Commentary
By William B. Ershler, MD
Synopsis: Evidence is presented from a case-control, retrospective analysis indicating a small but significant increased risk of cancer, particularly hematologic malignancy, among blood donors with a positive direct antiglobulin test (DAT).
Source: Rottenberg Y, et al. Blood donors with positive direct antiglobulin tests are at increased risk for cancer. Transfusion. 2009;49:838-842.
A positive, direct antiglobulin test (DAT) is the result of the presence of antibody on the red cell surface, and is detected in less that one in 1,000 blood donors.1
Positive direct antiglobulin tests are more common with advancing age, and have been associated with both autoimmunity and lymphoproliferative disorders. However, it is unknown whether DAT+ in healthy blood donors is associated with an increased risk of malignancies.
In the current study, all blood donors with DAT+ samples were identified during the years 1999 through 2003 through the Magen David Adom National Blood Services in Israel. This study compared the risk of cancer among 586 DAT+ and 2,344 DAT- donors who were matched according to sex, age, and year of donation. The risk of cancer in DAT+ donors was also compared to expected rates in the general Israeli population. Cancer was ascertained through the Israel Cancer Registry.
Malignancies occurred among 17 (2.9%) of the DAT+ and 27 (1.2%) of the DAT- blood donors; of these, three donors in the DAT+ group were diagnosed with hematopoietic malignancies within 12 months of their donation. Even after excluding these early cases, the relative risk of developing cancer was 2.14 (95% confidence interval [CI], 1.13-4.10), comparing DAT+ with DAT- donors, while the relative risk for hematopoietic cancer was 8.3 (95% CI, 1.5-43.2). Comparing DAT+ blood donors with the general population, the standardized incidence ratios (observed/expected cases) were elevated at 2.11 (95% CI, 1.15-3.54; p = 0.16) for all malignancies and 8.03 (95% CI, 2.2-20.6; p = 0.003) for hematologic malignancies.
Commentary
These findings support an increased risk of cancer, particularly hematologic malignancies among presumed healthy volunteer blood donors who are found to be DAT+. Current policy at blood donation centers, as described by Kamel and Tomasulo in their accompanying editorial2 is to defer a DAT+ donor for six months with a reassuring letter to the donor that a positive DAT is observed in healthy people but also may be associated with certain medications, viral infections, autoimmune disorders, or hemolytic anemia. The subject also is encouraged to share this information with his/her physician for consideration of additional workup. With the information provided by the current study, the concern regarding an associated malignancy is at issue. However, the findings should be considered preliminary and not sufficiently robust to warrant a change in policy. Discussion with the primary physician could be undertaken (with the donor's permission), and any additional evaluation might be considered in the context of other clinical parameters that indicate cancer risk. This approach might be re-evaluated if subsequent studies confirm the association of DAT and malignancy. In this regard, data from several large blood centers in the United States and elsewhere should be rigorously examined and prospective epidemiologic studies undertaken. Furthermore, if the association is confirmed, demonstrating an explanatory mechanism might enhance the understanding of the relationships that exist between host immunity and neoplasia.
Finally, on a related note, it is quite possible that if potential donors who are deferred because of low hemoglobin levels are actively referred for an explanation of their anemia, early colon cancers might be detected at a stage where cure is more likely.
References
1. Mehta K, et al. Positive direct antihuman globulin test in normal blood donors. N J Med. 1987;84:265-267.
2. Kamel H, Tomasulo P. A healthy donor or unsuspecting patient. Transfusion. 2009;49:818-820.
Evidence is presented from a case-control, retrospective analysis indicating a small but significant increased risk of cancer, particularly hematologic malignancy, among blood donors with a positive direct antiglobulin test (DAT).You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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