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FDA’s BPAC Evaluates Use of NAT to Reduce the Risk of Transfusion-Transmitted Malaria

May 17, 2024

May 2024

Claire Whetzel

Claire Whetzel is the editorial coordinator for ASH Clinical News.

Members of the U.S. Food and Drug Administration’s (FDA) Blood Products Advisory Committee (BPAC) met to evaluate proposed strategies of incorporating the nucleic acid test (NAT) cobas Malaria to selectively screen blood donations to reduce the risk of transfusion-transmitted malaria (TTM). This discussion comes shortly after the test was approved in March 2024.

Malaria, a mosquito-borne disease frequently characterized by high fevers, chills, and flu-like illness, is primarily contracted in African countries and no longer endemic in the U.S., though rare locally acquired cases have been reported, largely in Florida. Malaria can also be acquired through the transfusion of blood and blood components from infected donors, with 93 cases of TTM reported from 1963 to 1999 and 13 cases reported from 2000 to 2021.

Current methods to reduce the risk of TTM are the donor history questionnaire and the FDA’s recommendations for malaria risk, which include criteria such as no history of malaria or history of residence in a malaria-endemic country for the past three years and no history of travel to a malaria-endemic area within the past three months. However, these methods of donor history screening can be incorrectly interpreted by staff or erroneously reported by the donor, and deferral periods may be insufficient to identify asymptomatic cases or may disqualify healthy donors.

The first issue for discussion pertained to the FDA’s two proposed strategies for using the cobas Malaria test:

  • Selective testing of individuals who have a history of malaria, history of living in a malaria-endemic country, or history of travel to a malaria-endemic area
  • Required testing of all donors and selective testing of individuals with a history of malaria or travel to a malaria-endemic area

In evaluating the two strategies, members of the BPAC affirmed the importance of adding more blood from diverse populations to the blood supply. BPAC member Sridhar Basavaraju, MD, of Emory University School of Medicine in Atlanta, explained, “We have periodic shortages of certain blood groups … There’s benefit to not having to unnecessarily defer people just because of malaria risk for which you have a viable test.”

However, when it came to choosing between the two strategies, members acknowledged that both have limitations, especially regarding their testing burden. Evan Bloch, MD, MS, associate professor and associate director of transfusion medicine at Johns Hopkins University School of Medicine in Baltimore, said, “The testing is robust and exquisitely sensitive, but the question seems to be less about whether selective testing will be effective and rather whether the risk actually merits the cost and complexity of intervention.” He continued, “There is less than one case per year [of TTM]. We’re looking at a risk of about one in 10 million.”

The second strategy was especially criticized by several members as “overkill,” though Dr. Basavaraju pointed out, “There are one to two countries per year that are no longer malaria-endemic and have achieved malaria eradication. It would seem difficult for a blood center to … figure out if, during [a donor’s] time of travel or residence, that country was malaria-endemic.” He argued that the second strategy’s “one-time testing would allow for a clean slate [in which] you could risk-stratify donors in real time and test them accordingly.”

Additionally, Melissa Cumming, MS, senior epidemiologist at the Massachusetts Department of Public Health, who ultimately voiced her preference for the first strategy, conceded that the second would capture process failure cases that would be overlooked by the first.

Other attendees of the committee meeting, including Suchitra Pandey, MD, chief medical officer of Stanford Blood Center, called into question ― especially considering increased testing burden ― the necessity of implementing either strategy. She argued that the current use of a questionnaire for donors and subsequent deferral of those who do not meet qualifications is safe and said that blood centers need testing flexibility. “Blood centers are very different with their current risk based off their donor populations,” she said. “If a donor center already has a donor population [without] as many travel or residency deferrals, [they should have the option] to continue using [the deferral system].”

The second question posed during the meeting ― whether blood establishments should implement time-limited NAT screening of all donations collected in areas of the U.S. when a single case of locally contracted malaria has been reported ― proved easier for BPAC members to agree on. “There are a lot of challenges in identifying a single case of malaria,” Dr. Basavaraju said. “The investigation can be very time-consuming. By the time everything is sorted out and reported, it’s possible that the risk would pass.”

Though members of the committee did not vote on either question and opinions proved diverse, Brenda Grossman, MD, MPH, professor in the Department of Pathology and Immunology at the Washington University School of Medicine in Saint Louis, summed up the members’ common interest: “The outcome we want … is a diverse, safe, available blood supply. There is more than one way to get that.”

Source: FDA, May 9, 2024.

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