Hyper acute stroke unit services

Simon Liu and colleagues (Clin Med June 2011) should have clarified that the quoted number needed to treat (NNT) of 3.1 with thrombolysis did not refer to the more often used group outcome comparison of ‘independent’ versus ‘dependent and dead’, but to expert derived estimates for one additional patient to have a better outcome by one or more grades on the mRS (modified Rankin Score).^1,2 This would include patients moving from mRS 5 to mRS 4, for example, who would remain in the ‘dependent and dead’ category of outcome.

Jeffrey Saver's 2004 modelling paper concluded ‘for every 100 patients with acute stroke treated with tissue plasminogen activator, approximately 32 will have a better final outcome and three have a worse final outcome as a result of treatment’. Thrombolysis has the potential to harm as well as cure! Saver also stated in the paper ‘the NNT for tPA treatment to avert one case of dependence or death after stroke, defined as an mRS of 2 or more, is 8.4’ based on the NINDS study.² A NNT of 8–10 is probably more recognised by physicians for the effectiveness of thrombolysis.

Work from Australia documenting the real-life three-month outcomes after thombolysis suggests that Saver's experts may have underestimated the benefits of thrombolysis in the group of patients presenting with more severe strokes.³ Bray and colleagues in Melbourne found that of 24 patients presenting with stroke and a mRS of 4, the outcome at three months was that five of the group had an mRS of 0, 6 mRS of 1, 3 mRS of 2, 5 mRS of 3 and 1 an mRS of 4. Only four patients had a worse outcome with one dying (mRS 6) and three having a mRS of 5. For the 43 patients presenting with a mRS of 5 there were similar favourable improvements; 19 returned to independence (mRS 0–2) at three months post-stroke, with a further six dying and five remaining on a mRS of 5.

The access to hyper acute stroke care and thrombolysis in London has improved in recent years. Those people with severe strokes in particular need to get to hospital as soon as possible because early thrombolysis could make a major difference to their future care needs.

• © 2011 Royal College of Physicians