People who suffer the most common type of stroke should be given a genetic test to find out which drugs can prevent future attacks, a watchdog has said.

The National Institute for Health and Care Excellence (Nice) said people who have had an ischaemic stroke – where a clot blocks the flow of blood and oxygen to the brain – or a transient ischaemic attack (TIA) should be tested on the NHS.

In new draft guidance, the watchdog said medics who are considering giving the drug clopidogrel should first reach for the genetic test.

Clopidogrel is a common drug which prevents platelets – a type of blood cell – from sticking together and forming a dangerous blood clot.

Nice currently recommends clopidogrel as an option for treating people at risk of having another stroke but it is not suitable for people with certain variations in a gene called CYP2C19 because they cannot convert the drug properly for use in the body.

The genetic test would help overcome this by finding people with these variants so they can be treated with an alternative drug.

Some 32% of people in the UK are thought to have at least one of the CYP2C19 gene variants.

Evidence has suggested they have about a 46% increased risk of another stroke when taking clopidogrel compared to people without the variants.

If laboratory testing – estimated to cost around £139 per test – is not possible, Nice said the Genomadix Cube test costing £197 and given at the bedside can be used instead.

There are around 100,000 strokes every year in the UK, of which around 43,000 are recurrent strokes.

Every year, 46,000 people in the UK have a TIA for the first time, which is seen as a warning that they are at risk of stroke.

Mark Chapman, interim director of medical technology and digital evaluation at Nice, said: “The recommendation is a step forward in ensuring people who have had a stroke receive personalised care thanks to a genetic test run after their DNA is sequenced using their blood or saliva.

“Treatment with clopidogrel is effective in preventing further strokes for the majority of people who don’t have the gene variant.

“But, until now, doctors have not known who cannot be treated with clopidogrel until after they’ve had a second stroke or TIA and that could be too late.

“If the CYP2C19 variants are found, other treatment options can be used.

“This test ensures we’re getting the best care to people quickly, while at the same time ensuring value for money for the taxpayer.”

Around 11 million items of clopidogrel are dispensed each year at a cost of around £16 million to the NHS, Nice said.

The draft guideline is subject to consultation.