Distribution of disease

[Guest]

Hi,
I am not a maths guy, and am working on an article for a narcolepsy support group.

The problem is this:

The number of people in the general population who suffer from narcolepsy is estimated to be 1 in 2000
90% of people who have narcolepsy have the HLA-DQB1*0602 genetic marker.
25% of the population have the HLA-DQB1*0602 genetic marker.
So it seems logical to say that the number of people in the population who have HLA-DQB1*0602 genetic marker who have narcolepsy would be 1 in 500 Is that correct?

And what would be the number of people in the population who do not have the HLA-DQB1*0602 genetic marker who have narcolepsy?

Thanks in a advance,

Philip

[shyamjayakannan]

No that conclusion is incorrect. The data says 1 in 2000 people have narcolepsy. Now, 90% of these have the genetic marker, which means those who have both would be [tex]\frac{1}{2000}\times\frac{90}{100}\approx\frac{1}{2223}[/tex] or 1 in 2223 people have both.

As for those with narcolepsy, but without the gene marker, that is 10% of those with narcolepsy (because 100 - 90 = 10) or [tex]\frac{1}{2000}\times\frac{10}{100}=\frac{1}{20000}[/tex] or 1 in 20000.

The data basically shows that there is a strong correlation between having the condition and carrying the gene marker.