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ABCD2 tool 'inaccurate as a predictor of stroke'

By Christian Duffin

A tool used by GPs to identify patients who have had a transient ischemic attack who are at risk of further strokes is not sensitive enough to distinguish between high and low risk patients, according to new research.

They argue that the ABCD2 tool has only limited clinical application and concluded it is 'inaccurate, at any cutpoint, as a predictor of imminent stroke.'

The findings contrast with stroke guidelines by NICE published in 2008, which state that people who have had a suspected TIA should be assessed as soon as possible for their risk of subsequent stroke using the ABCD2 tool.

GPs should give patients with an ABCD2 score of 4 or above 300mg aspirin daily and refer them for to a specialist assessment within 24 hours. SIGN guidelines also back the ABCD2 tool for use in Scotland.

The researchers enrolled 2,056 patients with an average age of 68 who had received a final diagnosis of TIA or minor stroke at one of eight emergency departments in Canada between 2007 and 2010. They wanted to examine how good the ABCD2 was as a predictor of stroke within seven days or 90 days.

Patients with an ABCD score of more than four had a sensitivity of 65.8% and a specificity of 57.2% for predicting stroke risk at seven days and a sensitivity and specificity of 43.6% 56.8%, respectively, for predicting TIA risk at seven days.

The researchers concluded: 'We believe that the sensitivities we found are too low to be clinically acceptable', and that the low specificity meant GPs risked 'classifying almost all patients as requiring immediate imaging and perhaps admission to hospital.'

Study leader Professor Jeff Perry, associate professor in emergency medicine at the University of Ottawa, said: 'The criteria used to calculate the score are not sensitive enough to classify patients as being at low risk.'

Dr Alan Begg, a GP in Montrose who has advised SIGN on stroke guidelines, said: 'When I do workshops on this with GPs they pull their hair out at the thought of all the scoring systems. I question how much use is being made of scoring systems in general practice. All TIAs carry a huge risk of developing a full blow stroke. The most important thing about TIAs is that GPs get a good clinical history.'

But Dr Dan Lasserson, a GP with a research interest in stroke and clinical lecturer in general practice at Oxford University, said that GPs should carry on using the ABCD2 scoring system. 'In the UK we say that a score of four of more should mean that TIA patients should be seen at a TIA clinic within 24 hours. The research says that the sensitivity is lowest for scores of 6 and 7, but we use a lower cut-off point than that for our referrals.'

Canadian Medical Association Journal 2011, online 6 June

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