Thursday, January 10, 2008

My View on Organ Donation

On Monday, the story about Health Canada's new regulations for organ donation broke. CBC reported on the rules, which came into effect in December and prevent several high risk groups from donating. Included among these groups are injection drug users, people with tattoos, and any men who had sex with other men in the previous five years.

After reading the article, I went to CBC's Your View section to read some comments. As expected, there was a range of opinions, from outrage to blatant homophobia. What I found particularly troubling was the way people were misreporting, misinterpreting, misstating, and downright making up various numbers to try to back up their arguments. So, I set down to find some actual numbers and do some very rough calculations to try to interpret them. When I went to post my analysis, I discovered that they have a 2000-character limit. So, I broke it into two pieces and was able to post the first half. But, for whatever reason, the second half never appeared. I checked their Submissions Policy and found no restriction on multiple, related posts, so I tried submitting it again from another IP address, just in case they automatically screen out multiple submissions as a guard against spam. No dice, so I guess someone actually reviewed it and decided not to post it. Anyhow, the discussion is now closed, so I figured I'd just post it here...

First off, in response to the ridiculous non-statistics that have been bandied about, I'd like to offer some actual figures and back-of-envelope calculations.

2005 HIV Infection Numbers (from Health Canada):

58,000 HIV-infected people in Canada
29,600 are MSM (men who have sex with men)
2,250 are MSM-IDU (injecting drug users)

You'll notice that about 50% of HIV infected people in Canada are men who have had sex with men. Some people have inverted this claim and said that 50% of MSM are HIV-infected, which of course, is not at all the same thing. As we'll see in a moment, the real number is a tiny fraction of that.

Canada's population in 2005 was approximately 29,271,200. That's interpolated from the 2001 and 2006 census numbers (from Wikipedia: Canada).

I'll work on the assumption that 2.5% of the population are MSM. Of course, various studies have offered wildly differing figures, but I think it's reasonable to assume that 5% of men have had sex with men as a "consensus figure" for my rough estimations (from Wikipedia: Demographics of Sexual Orientation). Of course, I've halved that since I'm looking for the percentage of the population as a whole.

Using these figures, let's estimate HIV infections rates among...

MSM: 29600 / (0.025*29271200) = 0.040
MSM+ISU: (29600+2250) / (0.025*29271200) = 0.044
Non-MSM: (58000-29600 - 2250) / (0.975*29271200) = 0.00092

So, by my rough estimate, 4% of MSM are infected with HIV, compared to just under 0.1% of the rest of the population.

As a gay man, I find that pretty alarming. A man who has sex with men is more than 40 times more likely to be HIV+ than anyone else. The immediate reaction might be to take the steps that Health Canada has taken. But of course, a couple of statistics don't tell the whole story.

What you really have to look at is how small a risk those numbers actually represent. All donated tissues are tested, and those tests are considered to be highly effective, with false-negative rates of just 0.003% for HIV testing (from Wikipedia: Accuracy of HIV Testing). So, multiplying that out, we can estimate the chances that a donated organ that tests negative for HIV will actually carry the disease...

MSM: 0.04*0.003 = 0.00012
Non-MSM: 0.00092*0.003 = 0.00000276

Yes, that's right. A negative-testing organ from an MSM is "only" 99.988% safe, while a negative-testing organ from someone else is 99.999724% safe.

Now, given the choice, who wouldn't want the safer organ? But, of course, that's not the choice we face in reality. There is a chronic shortage of donated organs available and people are dying on the waiting lists. That's why those people in need of organs are willing to take that extra risk, as they expressed in their responses on the CBC's forum.

So, the appropriate question to ask is this: does the benefit of additional organ donations outweigh the increased risk of infection? My figures, while just estimates, suggest that it does, and by far. If we also apply the 2.5% MSM estimate to the pool of organ donors, then we can calculate the overall risk when they are included in the system:

Total: 0.025*0.00012 + 0.975*0.00000276 = 0.00000569

Removing this "high risk" 2.5% of the donor pool improves the safety of the system by a mere 0.000293%. The numbers strongly suggest that we're best served by maximizing the size of the donor pool and relying on existing, highly effective testing to identify unsafe organs. Even if these estimates are out by orders of magnitudes, how can the new regulation possibly be justified? Of course, if it had been debated in the open, we would be able to see and evaluate Health Canada's reasoning. But, I'd suggest, the way it was adopted in secret and announced a month later doesn't reflect well on that reasoning.

Gay and bisexual men may feel unduly targeted by this regulation, but we're not its real victims. Those people in need of organ transplants are.