Thursday, July 19, 2007

How small is 0.3%?

0.3%, the estimated ratio of HIV positive people who are not aware of it.
0.3% is 0.3 per 100, or 3 per 1000, or about 1 per 350.
Seems small..
Consider these:
The population being studied were from blood samples collected at hospitals.
It is sort of bias towards people whose blood were for some reason collected at hospitals.
Nevertheless, it is not obvious that there are more or less "high-risk" behavior people in this group as compared to the general population.
On the other hand, it is obvious that vast majority of the population do not practice "high-risk" behaviors, and it is reasonable to believe that majority of these 0.3% are those who have "high-risk" behaviors.
Thus, my message to those who want to feel that 0.3% is very low and continue your "high-risk" behaviors:
Among the high-risk communities, the ratio is much higher than 0.3%.
For example, if we assume that there are 10% high-risk behaving people, and among these, 50% do not feel that they are infected without recent testing, then the 1:350 ratio might become 0.5:35, or 1:70 or 1.4%!
Personally, I believe 10% is too high an assumption, and 50% too low. What if it were 1% and 90%? Then we have 0.9:3.5, or 1:3.85 or 25.7%!!!

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