Monday, February 19, 2007

Pharoah, let my people donate blood: Since 1985, the Red Cross has disallowed blood donation from any man who has had sex with another man since 1977. At the time, this made sense, given the limited reliability and high rate of false negatives of the AIDS testing regime. But, Bill Hooker at 3 Quarks Daily argues, today, the logic behind this ban no longer applies, so we are excluding a critical supply of blood donors for purely non-scientific reasons. I once had administered a lunchtime debate about this, in college, and I made almost the same argument, and was told by a Coulter acolyte, “Gay sex is inherently risky and immoral behavior. We should not reward it.” The opposition is not logical any longer. From 3QD:

A variety of expert presentations at a March, 2006 FDA workshop on behaviour based donor deferrals indicated that, with the advent of [nucleic acid testing], the window period for HIV infection is less than 12 days. In the US, the residual risk of transmission of HIV or HCV by blood transfusion is estimated, by a variety of models, to be around 1 in 2,000,000 donations. This is clearly a very conservative estimate, since there are around 15 million donations every year and I could only find mention of four authenticated transfusion-related transmissions of HIV since NAT was implemented in 1999 (none of which involved [men who have sex with other men]). At the same FDA workshop, Celso Bianco re-ran an earlier prediction using risk and other estimates that were getting general agreement at the workshop and came up with a figure, which he called conservative, of one infected unit per 32 years.

So, while it seems intuitively likely that including a high-risk group (as judged by increased prevalence) in the donor pool would increase overall risk, calculating — or rather, estimating — that increase is far from straightforward. The only numbers I could find were presented by Andrew Dayton to the same FDA workshop:

The 5-year [deferral, instead of a lifetime ban] would result in possibly a 25 percent increase in the current residual risk, and the 1-year would be 40 percent.

So, worst case scenario: 1.4 transmissions per 2 million donations, instead of 1.0 — or about three extra cases per year (and remember that, to date, the observed level of transmission is much lower than the estimate). I’m not familiar with what sorts of risks are considered acceptable in public policy formation, but I can say outright that I would be prepared to accept that risk to my own person as the cost of allowing MSM to participate on a more equal footing in a profound act of community altruism. (To say nothing of a 1% increase in a critical health resource that is often in short supply.)

Furthermore, given that the window period is less than two weeks and you can only donate every eight weeks, there is an obvious method for reducing the risk even further. According to the AABB, red blood cells can be stored cold for 42 days or frozen for ten years, and plasmaand cryoprecipitated antihemophilic factor can be frozen for at least a year; of the fractions into which whole blood is routinely divided, only platelets have a shorter effective storage life, about five days. It is clearly possible to hold (at least most of the fractions of) any first-time donation until the donor returns and can be re-tested; two clear tests eight weeks apart are definitive proof of HIV-negative status.


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