Comments on: Testing-testing: Two SNPs for $200

By: PathDoc15

PathDoc15 — Sat, 20 Oct 2007 15:00:18 +0000

Gretchen – I view pathology as the last line of defense against inappropriate testing, and the champions of best practices when it comes to laboratory medicine. Raising awareness (publishing) and educating your clinician colleagues on best practices when it comes to new technologies and discoveries is our responsibility. Unfortunately, we are often up against very persuasive marking forces… Certainly, there are a wealth of very good molecular tests that have dramatically impacted patient care. We just need to keep the bar high.

Concerning warfarin – a prospective study showing that a patient population that is dosed based on CYP2c9 and VKORC polymorphisms does better than a patient population dosed by best clinical judgement would go a long way towards appeasing the skeptics.

Several key pieces of data were not discussed in the current studies which would also add weight to the utility of SNP testing in this context. For example, what was the dose of warfarin when individuals had their negative event, what was their INR at that time, what was their INR and dose at their previous visit. etc.

By: Gretchen Galliano

Gretchen Galliano — Thu, 18 Oct 2007 00:21:02 +0000

Yes this is exactly the focus of the post– i am wondering if this will be a shift for us all not only for common medical disease but extending to solid tumors etc. we already see this in some manner in leukemia/lymphomas where some places have focused FISH panels for prognostication for LPD/MPD

this warfarin sensitivity is a very real step into an era of personalized pharmacogenomics —

By: PathDoc15

PathDoc15 — Wed, 17 Oct 2007 10:56:36 +0000

A big problem in the near future is vast proliferation in the number of SNP association ‘diagnostic’ or ‘prognostic’ tests. This is a fine example. What does one do with a 1.8 fold increased risk. Is this meant to be a screening test to save on the cost of actually having people go to the doctor and get a physical exam (not that!)? If so, what is the positive and negative predictive value? Sensitivity? Specificity? Would using this test impact patient outcome in any way? Let’s face it this is the bottom line (aside from the actual bottom line).

This story reminds me of the FDAs recent recommendation to test certain polymorphisms in VKORC and CYP2c9 in patients who are to be put on warfarin. Unfortunately, although there is loads of data to show that people with certain polymorphisms are more prone to negative events and require either more or less warfarin to achieve a steady state dose, there is no data to prove that testing for these polymorphisms actually impacts patient outcome. An editorial for another day…