SNPwatch gives you the latest news about research linking various traits and conditions to individual genetic variations. These studies are exciting because they offer a glimpse into how genetics may affect our bodies and health; but in most cases, more work is needed before this research can provide information of value to individuals. For that reason it is important to remember that like all information we provide, the studies we describe in SNPwatch are for research and educational purposes only. SNPwatch is not intended to be a substitute for professional medical advice; you should always seek the advice of your physician or other appropriate healthcare professional with any questions you may have regarding diagnosis, cure, treatment or prevention of any disease or other medical condition.NEJM, showed that those people who carried one or more copies of a function-reducing variation in the CYP2C19 gene that (referred to as *2, *3, *4 and *5) had 1.53 times the risk of having a heart attack, stroke or dying from cardiovascular causes compared to non-carriers. The risk of a stent-blocking clot (in those patients who had stents implanted during angioplasty to keep their arteries open) was increased three-fold.The second NEJM report, from researchers at several Paris hospitals led by Tabassome Simon, showed that in a group of 2,208 heart attack patients taking clopidogrel, carrying two CYP2C19 variants (any combination of *2, *3, *4, or *5) led to a 1.98 times increased risk of heart attack, stroke or death from any cause. Among the 1,535 patients who underwent angioplasty while in the hospital, having two function-reducing CYP2C19 variants increased the risk of cardiovascular events by 3.58 times.Unlike the study from Mega et al, Simon and colleagues did not see an increased risk in those people with only one copy of a CYP2C19 function-reducing variant.Finally, Jean-Philippe Collet and colleagues (also from Paris, France) followed the outcomes for 259 young (< 45 years old) heart attack patients taking clopidogrel. Their results, published in The Lancet, showed that having one or two copies of the CYP2C19*2 variant increased the risk of a second heart attack by 4.54 times. The risk of a stent-blocking clot increased 6.02 times.Collet et al did not investigate the other CYP2C19 variants included in the other reports.(23andMe customers can check whether they carry any of the CYP2C19 variants mentioned in these reports, except for CYP2C19*5, using the Browse Raw Data feature. See the table at the end of this post for more information.)Although the magnitude of the effect of CYP2C19 variants was different in each report, all three did show that versions of the CYP2C19 gene that reduce its ability to activate clopidogrel also increased the risk of a second cardiovascular event in those patients who have already suffered one. Based on these results, both Simon et al and Collet et al suggest that genotyping patients might be a good alternative to the current practice of monitoring their platelet response to clopidogrel.But in a commentary accompanying the report in The Lancet, Dr. Robert Storey of the Cardiovascular Research Unit at the University of Sheffield School of Medicine, UK, argues that testing platelet function in patients is faster than genotyping, and has the added benefit of finding patients who are not responding to clopidogrel due to factors other than CYP2C19 variants, such as age, diabetes, renal failure and cardiac failure.“Genotyping of patients with acute coronary syndrome is not necessarily the appropriate solution without further work to validate such an approach,” he writes.