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Genetic Test Recommended for Clopidogrel Use After Stroke

Clinicians should offer a genetic test to people who have had an ischaemic stroke or transient ischaemic attack to determine whether they can be treated with the drug clopidogrel to reduce the risk of blood clots and prevent secondary occurrence, the National Institute for Health and Care Excellence  (NICE) said.

Laboratory-based genotype testing should be the preferred option to screen for certain variations in the CYP2C19 gene that would make clopidogrel unsuitable for use, because those patients might be unable to metabolise the drug to its active form, NICE said in new draft guidance. Where laboratory testing was not possible, such as after discharge from an acute stroke ward, patients should be offered the Genomadix Cube point-of-care test, NICE said.

The appraisal committee said clinical experts agreed that patients found to have the 'loss-of-function variants' should be offered alternative antiplatelet treatment, despite uncertain evidence on the benefits.

Variant Levels Can Vary by Ethnicity

The CYP2C19 gene has many alternative alleles, which produce CYP2C19 enzymes with different levels of activity. The clinical function of each allele is classified as either normal function, no function, decreased function, increased function, or uncertain. The most common loss of function allele occurs in around 15% of people from a European background, 18% in people from an African or Caribbean background, and between 27% and 28% in those with Asian family heritage.

Evidence has suggested that people with these variants have around a 46% increased risk of another stroke when taking clopidogrel compared with those who do not have the variants.

At present no testing takes place to find out who is suitable for treatment with clopidogrel, which has an annual dispensing rate of 11 million items each year, at a cost to the NHS of around £16 million.


Clopidogrel genotype testing was judged to be cost effective compared with not testing, the committee decided, with a laboratory test priced at £139 and a test using the Genomadix Cube, £197. However, lab genotype testing could be much cheaper, at £20 to £40, according to some evidence.

Mark Chapman, interim director of medical technology and digital evaluation at NICE, described the recommendations as "a step forward in ensuring people who have had a stroke receive personalised care". He said recommending genetic testing "ensures we're getting the best care to people quickly, while at the same time ensuring value for money for the taxpayer".

Juliet Bouverie, chief executive of the Stroke Association, said: "We know that many stroke survivors spend the rest of their lives fearing another stroke, so it's great to see that more people could be given appropriate help to significantly cut their risk of recurrent stroke."

Consultation on the draft guidance, which applies to England only, would continue until 7 June, with final guidance expected on 25 October, 2023.