Call to assess all patients before stroke treatment
One in four are aspirin-resistant
By Lilian Anekwe
Aspirin resistance is 'a real phenomenon' that affects up to a quarter of patients treated to prevent stroke, a key analysis has concluded.
Patients who are resistant to the anti-thrombotic effects of aspirin suffer far more adverse events than those sensitive to the drug's benefits, the researchers found.
They warned that every
patient in need of anti-platelet treatment should first be evaluated for their response to aspirin therapy.
The analysis of 17 clinical studies in 2,367 patients found 26 per cent were aspirin-
resistant, as measured by platelet response assays, the
research team reported at the International Stroke Conference in San Francisco this week.
Resistant patients suffered more strokes, heart attacks and graft failures than those responding well to treatment. Some 5.7 per cent died during the course of the studies, compared with 1.3 per cent of sensitive patients (see graph below).
Research leader Dr Michael Buchanan, professor of pathology and molecular medicine at McMaster University in Ontario, Canada, said despite the continuing debate, aspirin resistance 'kept rearing its ugly head' in the clinical literature.
'This provides convincing evidence the phenomenon of aspirin resistance is real. Aspirin is a really effective drug when it works, but there is a significant proportion in which it doesn't. These patients appear at greater risk of suffering an adverse clinical outcome while on aspirin.'
Dr Alan Begg, a GP in Montrose and chair of the Angus stroke network group, said aspirin resistance would be difficult for GPs to diagnose in general practice. 'In the US there are point-of-care test kits available. But in the UK we don't identify patients who are aspirin-resistant, and they end up having a second stroke.'
Dr Begg added that he hoped 'we can identify aspirin-resistant patients and offer them an alternative thrombolytic' – although Dr Buchanan said there was evidence of the same problem with clopidogrel.
'The recent data is that probably about 25 per cent of people are resistant to clopidogrel as well,' said Dr Buchanan.
• Looking for evidence-based data on aspirin? Go to searchmedica.co.uk