From the Journals

Blood donation intervals of 8 weeks safe for most donors

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Blood, iron, and altruism

Donating blood serves an important function in medicine, but the practices associated with blood donations do not consider the effect it has on the donors. The amount of blood that most donors give is around 500 mL, or about 10% of total blood volume. The ratio of iron to blood is 1:1, meaning that for each milligram of blood drawn, one milligram of iron is lost. Considering that women only have 250 mg of iron reserves and men have 1,000 mg of reserves, many frequent donors are at risk of developing iron deficiency.

This study found that the total units of blood collected increased with shorter inter-donation intervals, while secondary safety outcomes of hemoglobin and ferritin levels remained similar between short and long inter-donation interval groups. While overall health did not decline, short inter-donation donors reported symptoms consistent with iron deficiency, including dizziness, tiredness, and restless legs. Researchers found that “about 25% of men and women at the most frequent inter-donation interval had iron deficiency and a third had at least one deferral for low hemoglobin.”

Iron deficiency can be mitigated by iron supplements or by lengthening the time between donations, but this does not fully correct the issue. Some blood centers have already introduced ferritin screening and lengthened the inter-donation interval for donors found to have low ferritin concentrations. Given the advances in automated laboratory testing, information technology, and the high compliance of blood donors, individualized approaches for prevention of iron deficiency could be feasible.

Alan E. Mast, MD , is the medical director for the Blood Center of Wisconsin, and an associate professor of pathology and cell biology at the Medical College of Wisconsin, Milwaukee. Edward L. Murphy, MD , is resident professor of laboratory medicine at University of California, San Francisco, and an affiliate of the Blood Systems Research Institute. They made their comments in an editorial that accompanied the study.



Reducing the interval between blood donations from every 12 weeks to every 8 weeks increases blood units collected with little ill effects on donor quality of life other than symptoms related to iron deficiency, based on results reported by the INTERVAL Trial Group.

In the United States, men and women can donate blood every 8 weeks; the Food and Drug Administration and the AABB (formerly the American Association of Blood Banks) have considered lengthening the 8-week minimum inter-donation interval to reduce the risk of iron deficiency. The current practice in the United Kingdom is to allow men to donate every 12 weeks and women every 16 weeks, the authors noted.

Blood is drawn from a donor's arm blueskyline/Thinkstock
“More frequent blood donation is a feasible and safe option for donors in the U.K., and gives blood services the short-term option of more frequent collection from donors if the supply falls or demand rises,” wrote Emanuele Di Angelantonio, MD, of the University of Cambridge and National Health Service Blood and Transplant, and fellow INTERVAL Trial Group members. “Our study has provided the first randomised evaluation, including precise quantification, of key measures of efficiency and safety that blood services need to ... safeguard donor health and maintain the blood supply.

The INTERVAL study examined hemoglobin levels, ferritin levels, and self-reported symptoms as well as the number of blood donations over a 2-year period among 22,466 men randomly assigned to either 8-, 10-, or 12-week blood donation intervals and 22,797 women randomly assigned to donation intervals of 12, 14, and 16 weeks.

Men in the 8-week interval group donated significantly more blood on a per-donor basis, contributing 1.69 and 7.9 units more than the men in the 10- and 12-week interval groups, respectively. Similarly, women in the 12-week interval group contributed approximately 0.84 and 0.46 units more than did women in the 14- and 16-week interval groups.

Hemoglobin and ferritin concentrations stayed relatively stable throughout the study in men and women in all donation interval groups. The baseline hemoglobin and ferritin averages were 149.7 g/L and 44.9 mcg/L in men, and 133.9 g/L and 24.6 mcg/L in women, respectively. Ultimately, mean hemoglobin level decreased by 1%-2%. Ferritin level decreased by 15%-30%, indicating that it is a more accurate marker of iron depletion, the study authors wrote. The report was published online in The Lancet.

The researchers also analyzed self-reported symptoms associated with blood donations derived from donor follow-up surveys sent at 6-, 12-, and 18-month intervals. At the end of the 2-year study, donors underwent a series of cognitive function tests and answered a physical activity questionnaire. Increased donation rates correlated with increased symptoms of iron deficiency such as tiredness, restless legs, and dizziness. This effect was reported more strongly in men.

About 10% of participants were allowed to donate despite having baseline hemoglobin concentrations below the minimum regulatory threshold, said the authors, who said that the screening method used in the United Kingdom to test eligibility to donate needs to be reviewed.

“In response to these findings, we have started the COMPARE study (ISRCTN90871183) to provide a systematic, within-person comparison of the relative merits of different haemoglobin screening methods,” they wrote

The study was funded by National Health Service Blood and Transplant and the National Institute for Health Research Blood and Transplant Research Unit in Donor Health and Genomics (NIHR BTRU-2014-10024).

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