Gordon Brown’s in favour. So is the Chief Medical Officer, Sir Liam Donaldson, the Scottish National Party, Plaid Cymru, and other parties. But when the Organ Donor Taskforce was asked to look at presumed consent for organ donation, it said no.

A new analysis suggests that it failed to consider all the available evidence and reached the wrong conclusion.

The taskforce, which reported in 2008, did not recommend changing the current practice, which is based on people expressing while alive their intention to become an organ donor after their death by carrying a donor card or adding their names to the NHS Organ Donor Register. The alternative is a system of presumed consent in which everybody is assumed to be willing to donate organs after death unless they have, during their life, signed an “opt-out”.

Some countries, such as Spain, Belgium and France, operate under a law of presumed consent, with families retaining the right to override the deceased’s wishes. Austria has presumed consent without the right of override. The UK and the Netherlands have both rejected presumed consent.

In Saturday’s BMJ (and available already online) Sheila Bird, senior biostatistician, and John Harris, Director of the Institute for Science, Ethics and Innovation at Manchester publish a fresh analysis of the figures suggesting that presumed consent could, under plausible assumptions, produce an extra 2,880 donors over ten years in the UK, by increasing the likely number of donors from 6,050 to 8,930. That assumes that only 10 per cent of people opt out, that the right of families to object is retained, and that 10 per cent of families do in fact decline the request for organs.

At present, 40 per cent of relatives refuse, but if individuals are on the register the refusal rate falls to around 10 per cent. Members of ethnic minority communities are far more likely to refuse, in spite of the support of all major religions for transplantation.

The taskforce acknowledged that donation rates were higher in countries with presumed consent, adding, rightly, that this did not prove cause-and-effect. But, say Bird and Harris, the taskforce did not examine the UK’s donor audits (carried out at least three times in the past 20 years) to try to work out - under plausible scenarios - what additional numbers of solid organ donors there could have been in the past ten years after brain stem death.

Presumed consent would apply to around 3,000 brain stem deaths a year occurring in intensive care units. In the latest audit (2006-08) 1,186 of these became a source of organs, 49 per cent of the possible total once those ruled out for medical and other reasons, notably relatives’ refusals, are excluded. On the basis of this potential “pool” of donors, the authors calculate that over ten years, at current rates, 6,050 donors would be found.

This could increase to 7,060 if the consent rates that applied in the late 1980s were restored – a 30 per cent refusal rate by relatives against 40 per cent today. Presumed consent with an opt-out rate of 10 per cent and a relatives’ refusal rate of 10 per cent would produce 8,930 donors, but if the opt-out rate were to be 5 per cent and the refusal rate 40 per cent, this would fall to 6,280. Mandatory donation, in which neither the deceased nor their relatives are given any choice, would produce 10,280 donors, but this is included only for comparative purposes.

That means that presumed consent, on plausible assumptions, could deliver 68 per cent of the maximum possible number of donors (8,930 against 10,280) but that if relatives’ refusal rates remained high, presumed consent would produce only a slight gain or even a decline.

Much would still hang on relatives’ feelings, whatever the law. But the two authors conclude that presumed consent would be better than the present system. It would also be cheaper because the register would be much smaller, containing at most 6 million registrations against today’s 16 million. The alternative – continuing to recruit volunteers to opt-in, and campaigning to reduce refusals by relatives – has not been effective.

Reference: Time to move to presumed consent for organ donation by Sheila Bird and John Harris(BMJ 2010;340:c2188, 8 May, p 1010-1012)