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18 十一月 2016, 13:48
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FDA will rethink the ban on donating blood by men who have sex with men (MSM)

FDA will rethink the ban on donating blood by men who have sex with men (MSM) - 图片 1

After the magnitude of the June 12, 2016, massacre at the Pulse nightclub became clear, people throughout Orlando wanted to help in any way they could. Thousands volunteered to give blood; local restaurants offered free food and water to those waiting in hours-long blood-bank lines in the central Florida heat. Yet after this attack that specifically targeted the lesbian, gay, bisexual, and transgender (LGBT) community, one group was notably absent from these donation lines: men who have sex with men, who have been prohibited from donating blood in the United States since 1985. This prohibition was, of course, not the tragedy that day, but the added insult that gay and bisexual men were unable to offer this measure of help to their community was deeply felt.1 One week later, 24 U.S. senators wrote to Food and Drug Administration (FDA) Commissioner Robert Califf asking the agency to revisit this ban,2 and on July 28, 2016, the FDA announced a call for input about changes to this policy. The FDA is accepting comments through November 25, 2016 (https://www.federalregister.gov/documents/2016/07/28/2016-17804/blood-donor-deferral-policy-for-reducing-the-risk-of-human-immunodeficiency-virus-transmission-by).

Each day in the United States, 36,000 units of red blood cells, 7000 units of platelets, and 10,000 units of plasma are transfused into patients throughout the country.3 With excellent screening technologies in place, the risk of transmitting HIV through a blood transfusion is 1 in 1.5 million; the risk for hepatitis C virus (HCV), 1 in 1.1 million; and the risk for hepatitis B virus (HBV), 1 in 282,000.4 In fact, even excluding simple febrile reactions, the risk of serious, noninfectious complications — volume overload, acute lung injury, or life-threatening transfusion reaction — is closer to 1 in 100, exceeding the risk of infectious complications by orders of magnitude.4

The fact that no victim in Orlando who received blood products should expect a transfusion-related infectious complication both defines our current reality and belies a tragic history: during the 1970s and 1980s, the U.S. blood supply was the source of 20,000 HIV infections and more than 200,000 HCV infections among recipients of blood products.5 Though we believe that the current population-based ban on donation by men who have sex with men should be replaced with an individual risk-based assessment, it is also undeniable that the ban’s initial institution early in the AIDS epidemic was critical in the creation of a safer blood supply.

THE EARLY DAYS OF AIDS

By the end of 1982, mounting evidence suggested that AIDS was caused by a virus transmissible through blood and sex. Epidemiologists at the Centers for Disease Control (CDC) had been tracking the outbreak since 1981, when clusters of previously healthy men suddenly began dying of Pneumocystis jiroveci pneumonia, many of them with the previously rare Kaposi sarcoma, a stigmatizing mark of this new disease. Over the next year, cases of this immune system–ravaging syndrome spiked in the gay male community and among people who injected drugs. As cases cropped up among patients with hemophilia who had been receiving clotting-factor injections from pooled donor plasma, epidemiologists at the CDC became convinced they were dealing with a bloodborne pathogen. The immediate fear was that the national blood supply was contaminated with an unidentified and uniformly lethal virus.

In January 1983, public health experts at the CDC convened a meeting with leaders of the national blood banks. In a 2004 interview with PBS’s Frontline, CDC epidemiologist Don Francis recalled that his objective at that meeting was straightforward: to share data suggesting that the likely link among the AIDS outbreaks in the gay community, people who inject drugs, and patients with hemophilia was the blood supply, and then to encourage adoption of a policy banning blood donations from these populations. The logic was simple: with no test for the disease and only an early understanding of its mode of transmission, preventing donations from populations that were known to be disproportionately affected seemed a reasonable step.

But resistance to this suggestion came swiftly, and a ban was not instituted. Historians debate whether the blood-bank community’s intransigence regarding such a ban arose from denial about the magnitude of the threat, avarice in protecting its business interests, fear of breaking the taboo on public discussion of sex (especially homosexual sex), or some complicated combination of factors.5 To Francis, the refusal was unconscionable. Randy Shilts describes the meeting in his book And the Band Played On: “Don Francis pounded the table with his fist. . . . ‘How many people have to die? . . . How many deaths do you need? Give us the threshold of death that you need in order to believe that this is happening, and we’ll meet at that time and we can start doing something.’”6 It would be another 18 months, with thousands of transfusion-related HIV infections, before a ban was adopted nationally.

With the epidemic spreading, blood banks adopted a ban on donations from men who had sex with men in 1985, the same year that the first test for the disease was introduced. That move created the two-step screening process that exists today: a ban, euphemistically called a deferral, for certain populations identified when a volunteer completes a questionnaire, followed by universal testing of every donated sample.

 

PROGRESS AND STASIS

While scientific progress has since revolutionized HIV testing, the deferral strategy with respect to men who have sex with men has changed little. In 2015, a policy revision recommended that blood banks ban donations only from any man who has had sex with a man in the previous year, rather than at any time since 1977. Some, though not all, blood banks have adopted this updated recommendation, which many see as a positive incremental step. Still, the 1-year deferral is misaligned with the current science of HIV test characteristics and viral transmission.

Advances in HIV testing over the past 35 years can be characterized by two key improvements: progressive shortening of the window period (the time that a person is infected with the virus before a test can detect it) and improvements in the test’s sensitivity(how reliably the test can identify an infected person after that window period). In 1985, the FDA approved the first HIV-specific antibody test, then referred to as a test for the HTLV-III/lymphadenopathy-associated virus.7 By 1987, HIV test characteristics resulted in an estimated window period of 6 to 14 weeks. Assuming an 8-week window period, the risk of HIV transmission from the blood supply at the time was 1 in every 153,123 units of blood.8 Four generations of tests later, the sensitivity of HIV testing has increased from 97.3% in 1985 to just shy of 100% in 2016.9,10 In addition, every donated sample is also tested for HIV RNA, which results in a window period of 9 to 14 days. With updated tests, the risk of HIV transmission has decreased to 1 in 1.5 million.4 These advances in blood safety have everything to do with improved testing technology and nothing to do with progress in deferral practices.

A concern about allowing men who have sex with men to donate blood stems from the fact that in the United States, this population has a higher prevalence of HIV than heterosexuals. However, with near-perfect sensitivity of fourth-generation HIV testing after the window period, prevalence has minimal, if any, effect on the predictive value of a negative test result. Therefore, the risk of HIV in the blood supply comes mainly from the risk of donation during the first few weeks after infection. Any policy designed to protect the blood supply from HIV would focus on excluding potential donors — of any sexual orientation — at risk for having acquired HIV in the several weeks before donation.

 

INDIVIDUAL RISK

The following example exposes the flawed logic of the current policy: Client A, a married, monogamous gay man who, along with his husband, has for decades repeatedly tested negative for HIV cannot donate blood; however, Client B, a heterosexual man who has had unprotected sex in the past month with multiple women of unknown HIV status is allowed to donate. Clearly, there are at least two problems: Client B poses a higher risk of introducing HIV into the blood supply, yet currently he is not barred; and Client A has been told unequivocally that the medical community sees his blood as unclean, not because of high-risk behavior but because of the sex of his spouse.

The history of discrimination faced by the LGBT community, too often and in this case directly from the medical system,11 requires us to take every opportunity to advocate for the use of sound evidence to implement rational and transparent policies and to encourage honest engagement with health care. Indeed, it is not difficult to see how current policies drive LGBT patients to distrust medical care providers and to conceal their sexual orientation and gender identity, not only in the context of donation but in other medical settings as well.12 A risk-based questionnaire that encourages Client A and bars Client B is, of course, not a panacea for the health-related disparities faced by the LGBT community, but it is a step that represents our profession’s commitment to acting on our current best evidence rather than remaining mired in a history of our worst fears.

A policy change will require commitment, persistence, and political will, first manifested in further work to design an individual, risk-based questionnaire that is consistent with our current knowledge regarding transmission and test characteristics in relation not only to HIV, but also to other bloodborne infections for which the blood supply is tested. The ultimate decision about criteria for deferral according to individual risk regardless of sexual orientation should be based on a thoughtful analysis of the sensitivity and window periods of the tests for each type of infection.13

Other countries have grappled with this issue. In Europe, for example, Spain and Italy do not specifically ban men who have sex with men from donating; they have instead adopted risk-based deferrals.14 These countries provide important case studies to elucidate implications of nationwide policy changes regarding the eligibility of blood donors.

Transfusion of blood from one person to another will never be without risk, and it may not be possible to predict future bloodborne pathogens or the communities that will be most directly affected; indeed, the next big infectious culprit may well be vectorborne. Today, the Zika virus, carried by the aedes mosquito, looms as a potential threat, and the FDA now recommends universal testing of all blood donations for Zika virus — a decision consistent with the FDA’s cautious approach to blood safety.15 Babesia microti, a parasite carried by ticks in New England where the infection is endemic, has been transmitted through the blood supply,16 yet donated blood is not universally screened for this infection. Hikers and joggers who might come into contact with ticks are at risk for acquiring and transmitting babesia, yet of course we do not ban people engaging in such activities from donating blood. The FDA confronts a constant challenge as it seeks to maximize safety, assuage public fear, and prevent stigma — a complex mission that is best accomplished through rational policies that are frequently revisited in the context of updated science.

The ban on donations from men who have sex with men was instituted at a time of public health panic and vast uncertainty, but 31 years later, scientific advances in testing and in understanding of disease transmission offer new tools and better ways than a sweeping ban to minimize the risk of transfusion-related HIV. Thousands of people died from HIV that they contracted from the blood supply, and their memories demand that we not fall victim to the hubris of believing that there will not be emerging threats or new knowledge to be gained. Greatest respect can be paid to the people who died and to this tragic and complicated history not by maintaining outdated policies but by constantly reevaluating and implementing changes in line with what we do know and by advancing science in areas we do not fully understand. We must be committed to empirical rigor in the evaluation of the outcomes of any new policy changes, and in that way we can continue to ensure a safe blood supply for every person, of every community, who may need it.

http://www.nejm.org/doi/full/10.1056/NEJMms1613425 

作者: Liliya Ten

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