[morrow]

From wikipedia: "The vast majority of people (97%) have detectable antibodies by three months after HIV infection; a six-month window is extremely rare with modern antibody testing."

So if the transfer can work with a 3 month delay (I'm not sure if it can, just assuming), and the HIV test comes back clean, you're going to have a 97% chance of a true-negative, 3% chance of false-negative.

At that point, comparing it to the odds that the "eliglble" donor is lying about their sexual activities or is simply HIV positive and heterosexual, the ban on letting gays register seems draconian, and a scientific test-based approach seems better all around.

Especially when you consider that if no donor is found, the patient could die anyway. So if the only donor is gay, test them, and then notify the patient of the 3% chance of contracting HIV from a false-negative patient versus the 100% odds of dying from Leukemia, and see what decision they make.

http://en.wikipedia.org/wiki/HIV_test#cite_note-7

[cyrus_]

It isn't a 3% chance of a false negative, the 97% figure is conditioned on actually having HIV. The actual chance of a false negative is far lower, since most people don't have HIV at all.

[morrow]

Good point. You could also realistically eliminate those who know they are infected from the potential false-negative category, which would give you an initial pool of 240,000[1] potential infected who don't know they're infected. Among them there is a 3% chance of non-response within 3 months to antibody testing, for a total of 7,200 false-negative potential candidates out there among 309,000,000 total Americans. Then consider the 1 in 20,000 odds [2] of being a match, and you end up with a false-negative match rate of 0.00117 per million people (according to wolfram alpha [3]).

I probably screwed something up, but in any case you are definitely right that the false-negative odds are very low among all potential applicants. Really makes the argument against seem foolish.

1) http://www.cbsnews.com/8301-504763_162-57333212-10391704/cdc...

2) http://www.organtransplants.org/understanding/marrow/

3) http://www.wolframalpha.com/input/?i=%28%281%2F20000%29++*+%...