Doctors question whether all blood transfusions are effective and nece
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《英国医生杂志》
Evidence on the effectiveness of blood transfusion is severely lacking, and more research is needed. That was the main conclusion of a conference held last week at the Royal College of Physicians of Edinburgh.
The meeting was prompted by anxiety that too many resources may be being devoted to ensuring the safety of blood. The cost of supplying blood to the United Kingdom grew from ?50m ($480m; �365m) in 1995 to ?00m in 2004, and the increase is due mainly to new tests and processes to reduce the risk of transmitting infection.
Participants at the conference thought that some of the tests were undoubtedly needed but were concerned that the introduction of nucleic acid testing to supplement existing tests for hepatitis C cost between $5.8m and $8.4m for each quality adjusted life year (QALY) resulting from the avoidance of hepatitis C. (The National Institute of Clinical Excellence looks doubtfully at treatments that cost more than ?0 000 for each QALY.)
Most of the extra cost was due to the need to reduce the risk of transmitting variant Creutzfeldt-Jakob disease. The introduction of prion reduction filtration could add ?00m to the annual cost of the United Kingdom抯 blood service, participants were told.
Yet although the costs were high, it could be argued that the spending was necessary because it meant that the public still trusted the blood supply, said Ian Franklin, national medical and scientific director of the Scottish National Blood Transfusion Service. Excessive expenditure on safety was understandable, said Steve Kleinman, a professor from Victoria, Canada, as a reaction to the situation in the early 1980s when many people were infected with HIV through blood transfusion.
The main adverse effects of transfusion were currently not infection but severe haemolytic reactions (usually caused by transfusion of the wrong blood) and volume overload, said Professor Kleinman. He said that severe reactions occur in about 43 in every 100 000 red cell transfusions (95% confidence interval 39 to 48 per 100 000).
The emphasis on safety had not, however, been matched by an equal emphasis on effectiveness. Transfusion clearly saved lives in cases of major haemorrhage, said Dr Tim Walsh, a consultant anaesthetist in Edinburgh. But not enough research had been conducted on the question of when transfusion should be given in other circumstances. For example, randomised controlled trials looking at the triggers for transfusion involved fewer than 2000 people. Half of these patients were in one trial, with intensive care patients, that showed no benefit from transfusion. In this study the liberal use of transfused blood was not associated with any benefit, and among younger and less severely ill patients mortality was higher in patients who were given more blood (New England Journal of Medicine 1999;340:409-17). The numbers needed to harm for cardiovascular complications were 13 for any complication, 45 for myocardial infarction, and 19 for pulmonary oedema, Dr Walsh said.
Blood transfusion was clearly needed for life threatening blood loss, but probably only about a fifth of blood was used in such circumstances, said Dr Walsh. The conference also considered what was actually life threatening. How many Jehovah抯 Witnesses died because they were denied blood products? asked John Lilleyman, former president of the Royal College of Pathologists. Not many, he thought.
"Much more research is needed on the effectiveness of blood transfusion," concluded Marcela Contreras, national director of diagnostics, development, and research at the National Blood Service. "Keeping the blood supply safe is clearly important, but we have lost the plot in putting so much emphasis on safety and neglecting research into effectiveness."(Edinburgh Richard Smith)
The meeting was prompted by anxiety that too many resources may be being devoted to ensuring the safety of blood. The cost of supplying blood to the United Kingdom grew from ?50m ($480m; �365m) in 1995 to ?00m in 2004, and the increase is due mainly to new tests and processes to reduce the risk of transmitting infection.
Participants at the conference thought that some of the tests were undoubtedly needed but were concerned that the introduction of nucleic acid testing to supplement existing tests for hepatitis C cost between $5.8m and $8.4m for each quality adjusted life year (QALY) resulting from the avoidance of hepatitis C. (The National Institute of Clinical Excellence looks doubtfully at treatments that cost more than ?0 000 for each QALY.)
Most of the extra cost was due to the need to reduce the risk of transmitting variant Creutzfeldt-Jakob disease. The introduction of prion reduction filtration could add ?00m to the annual cost of the United Kingdom抯 blood service, participants were told.
Yet although the costs were high, it could be argued that the spending was necessary because it meant that the public still trusted the blood supply, said Ian Franklin, national medical and scientific director of the Scottish National Blood Transfusion Service. Excessive expenditure on safety was understandable, said Steve Kleinman, a professor from Victoria, Canada, as a reaction to the situation in the early 1980s when many people were infected with HIV through blood transfusion.
The main adverse effects of transfusion were currently not infection but severe haemolytic reactions (usually caused by transfusion of the wrong blood) and volume overload, said Professor Kleinman. He said that severe reactions occur in about 43 in every 100 000 red cell transfusions (95% confidence interval 39 to 48 per 100 000).
The emphasis on safety had not, however, been matched by an equal emphasis on effectiveness. Transfusion clearly saved lives in cases of major haemorrhage, said Dr Tim Walsh, a consultant anaesthetist in Edinburgh. But not enough research had been conducted on the question of when transfusion should be given in other circumstances. For example, randomised controlled trials looking at the triggers for transfusion involved fewer than 2000 people. Half of these patients were in one trial, with intensive care patients, that showed no benefit from transfusion. In this study the liberal use of transfused blood was not associated with any benefit, and among younger and less severely ill patients mortality was higher in patients who were given more blood (New England Journal of Medicine 1999;340:409-17). The numbers needed to harm for cardiovascular complications were 13 for any complication, 45 for myocardial infarction, and 19 for pulmonary oedema, Dr Walsh said.
Blood transfusion was clearly needed for life threatening blood loss, but probably only about a fifth of blood was used in such circumstances, said Dr Walsh. The conference also considered what was actually life threatening. How many Jehovah抯 Witnesses died because they were denied blood products? asked John Lilleyman, former president of the Royal College of Pathologists. Not many, he thought.
"Much more research is needed on the effectiveness of blood transfusion," concluded Marcela Contreras, national director of diagnostics, development, and research at the National Blood Service. "Keeping the blood supply safe is clearly important, but we have lost the plot in putting so much emphasis on safety and neglecting research into effectiveness."(Edinburgh Richard Smith)