A blood test that can help prevent stroke victims from having another attack is now being offered on the NHS in a move that experts say will save lives.

The test picks up genetic clues that show if patients will not respond to standard treatment – allowing doctors to switch them on to more effective drugs.

Experts say that roughly 25,000 Britons fall into this category, and until now it has been impossible to identify them.

It comes three months after The Mail on Sunday published details of a major report calling for widespread use of the genetic tests, which experts say could prevent tens of thousands of strokes and heart attacks every year.

Dr Alex Doney, a stroke specialist at Ninewells Hospital in Dundee, the first UK NHS unit to offer the test, says: ‘Genetic testing for stroke patients will save lives.

‘For years, we’ve treated stroke patients on a one-size-fits-all basis, meaning people with completely different genetic make-ups receive exactly the same dose of the same drug. Yet we know that for many patients, the current drugs work no better than taking a placebo.’

While the test is being used across 33 NHS hospitals in Scotland, the UK health watchdog, the National Institute for Health and Care Excellence (NICE), is reviewing it for more widespread use.

There are some 1.3 million stroke survivors in the UK. The attacks – the most common cause of disability – happen when there are problems with the blood supply to the brain.

There are two types. The most common is ischaemic stroke, where the blood supply is stopped due to a blood clot. These account for about nine in ten strokes.

It comes three months after The Mail on Sunday published details of a major report calling for widespread use of the genetic tests, which experts say could prevent tens of thousands of strokes and heart attacks every year. (Picture posed by model)

The other is a haemorrhagic stroke, which happens when there is a bleed on the brain because a weakened blood vessel that supplies the organ has ruptured.

This can happen for a number of reasons, including injury to the head, abnormalities in the blood vessels and bleeding disorders.

Most sufferers must take daily blood-thinning medication to prevent another stroke. The most common, for ischaemic strokes, is clopidogrel, which stops small blood cells…