Wednesday, November 27, 2013

A wee bit more on Genetic Determinism

The FDA is in a spat with the genetic information company  A lot of people on the web support the FDA, because they say 23andMe provides medical diagnosis and medical advice.  I really don't think so, I think they just take your genetic features and compare with the available scientific literature.    Anyway, it prompted me to look more closely at what they do.

To take a specific example, PBC (Primary Biliary Cirrhosis).  They give the scientific research 4 stars out of 4 for level of confidence.   They tell me that the average risk in European populations is 0.08%, i.e., on the average 0.08 out of 100 men of European ancestry will develop PBC between the ages of 20 and 79, assuming it is absent at age 20; and that in European men who share my genotype, the risk is 0.11%, i.e., 0.11 out of 100 men of European ancestry with my genotype will develop PBC between the ages of 20 and 79, assuming that it is absent at age 20". 

They tell me that this genetic marker has not been tested in people of African or Asian descent. Further, in the technical review, where they go into more detail, they say about a particular SNP and the risk of PBC associated with it (what is an SNP?):
Multiple studies have confirmed this association in populations with European ancestry. A Japanese study examined this SNP in an Asian population but was not able to confirm the association, possibly because the version of the SNP associated with risk in European populations is very common in Asian populations.
Notice the highlight.  As far as I can tell from Google searches is that the PBC incidence rate in China and Japan is not higher than that in Europe (but the numbers are sketchy).  It is believed to be rare in India also,  but suspected to be higher in migrant populations than in India.

Just another grain of sand that the whole system - whole genome and environment - will need to be considered in all but the simplest of cases.