Wednesday, March 24, 2010

PGx in DTCG? Doesn't stand up to Useful testing.

HT Don Rule today as well as the ENTIRE Pharmacogenomics Advisory Group that I am a proud member of.

Don wrote this comment a few days ago

"I was curious about what SNPs the DTC companies offer so I wrote a little applet ( to compare them to the SNPs in PharmGKB. It turns out the the Cytochromes are particularly sparse."

Well Don, you are correct. Even more so, as we began to review SNP data it became crystal clear on Monday.

The reason I was pissed about 23andMe doing the CF testing is because they missed hundreds of potential carrier alleles. What was even more so angering when I realized, you could be "tested" by one of these DTCG companies for "Plavix Metabolism" and come up with the absolute wrong answer.

Imagine that. Most people turn to DNA for an "absolute call" but when you don't look for the right SNPs or all of the needed SNPs, you miss a whole bunch.

Quick story. I had this pulmonologist physician, an elder statesman, super smart, Ivy league trained come up to me and say "Hey Steve, can you help me out?"

He is a sleep doctor too. He said "I have been trying to test for this narcolepsy gene and I can't get the right answer"

I said "Sure Dr. X, what do you mean 'keep getting the wrong answer'?"

He Said

"Well I am looking for HLA DQB1 and they keep telling me about this HLA DR, I have sent this test 3 times now and still gotten no information about HLA DQB1."

I did a big 'ol face palm.

Instead it searched for an imperfect haplotype......

That's the problem. If you don't test for exactly what you are looking for, you will never find it. Nor will you have the correct clinical answer.

If you only test 2 SNPs for CYP 2C19, you will never be able to accurately predict what someone's metabolizer status is.

What people should be using to assess metabolizer status of medications is something like the DMET Plus with additional PCR or another platform. AmpliChip does a nice job, but we have to be serious when it comes to medical care.

You Cannot, I repeat Cannot take the advice from 23andMe when it comes to metabolizer status for Plavix.

Please, please, please listen to me. Even 23andMe states it on their post about Plavix

This DTCG test is not ready to be used in the clinic or even trusted to tell your metabolizer status. Right now, they are not testing enough SNPs for me to be happy with it and use it in the office.

Don't stop your Plavix! Instead go get a clinical pharmacogenomic test done by someone who understands the limitations of the labs.

That drunk who lost their keys is still looking under the lamposts because that is where the light is..........

That is a stupid way to do clinical pharmacogenomics.

The Sherpa Says: Pretending to be clinical without standing up to clinical rigor is a recipe for disaster. I await the lawsuit from in stent thrombosis for the poor sap that trusts 23andMe enough to stop their Plavix.

1 comment:

cariaso said...

Kevin Davies has been tested by 23+decode+Navi and as a result has information on 1814 PharmGKB snps.

This is visible at

under Topics->PharmGKB.

Someone tested on only 23andMe would have the 1338 PharmGKB snps from that platform.

The companies probably are only reporting a tiny minority of those SNPs, but its not because their testing platforms are incapable.