- Email: [email protected]
Informed consent, risk, and blood transfusion
J
THORAC CARDIOVASC SURG
1990;100:88-91
Informed consent, risk, and blood transfusion Informed consent for blood transfusion bas become a necessity in light of the known risks associated with this service. AU transfusion services should institute written informed consent that clearly defines the patient's options, including the use of homologous blood, autologous blood, and directed donations. The risk of transfusion with an infectious blood product is dependent on the number of donors per recipient and the prevalence of undetected, contaminated blood in the tested blood supply. The chance that an adverse transfusion will occur can be calculated by use of these variables. Comparative risks can be explained to patients, thereby providing an understanding of the transfusion risk of human immunodeficiency virus, the human T-cell leukemia virus, and the agent of non-A, non-B hepatitis (hepatitis C).
Jerry Kolins, MD, Escondido, Calif., and Mark D. Kolins, MD, Detroit, Mich.
An
estimated 12 million units of blood are collected and transfused to approximately 3 million patients annually in the United States.' Although there are numerous adverse effects of receiving a blood transfusion, the concern of transfusion-transmitted infectious agents has received considerable attention since the recognition of the acquired immunodeficiency syndrome (AIDS). Transfusion-associated AIDS is rare; nevertheless it is the most feared complication of blood transfusion because the disease is fatal. This has led to intense scrutiny of the safety of the nation's blood supply, with resurgent interest in transfusion-associated hepatitis because transfusion-associated non-A, non-B hepatitis (hepatitis C) is more common than transfusion-associated AIDS and often results in cirrhosis and death? The reexamination of transfusion risk has motivated physicians to provide more information about transfusion risk to intended recipients of blood products. A natural evolution of this process includes written informed consent for this service. To enhance the consent process, tables have been constructed based on mathematic modeling; these provide rapid reference for the risk of recipient
exposure to an undetected, infectious unit in the blood supply.
Fromthe Community Blood Bank of North County and The Palomar Pomerado Health System, Escondido, Calif., and Department of Pathology, Detroit Riverview Hospital, Detroit, Mich. Received for publication June 2, 1989. Accepted for publication Aug. 14, 1989. Address for reprints: Jerry Kolins, MD, Community Blood Bank of • North County, 660 East Grand Ave., Escondido, CA 92025. 12/1/16323
Results
88
Methods The risk of receiving a unit contaminated with an infectious agent is directly dependent on the number of transfusions a patient receives: The more transfusions, the greater the risk. Assuming a 10% prevalence of a transfusion-transmitted agent in the donor population, Probability of uninfecteddonor = p = 0.9 Probability of infected donor = q = 6:1 p+q=1 If a recipient is exposed to two donors, the recipient may receive anyone of the following: two uninfected units, one uninfected unit and one infected unit, or two infected units. Mathematically this is expressed by the formula (p + q)2 = 12. The product of this squared binomial is p2 + 2pq + q2 = I. In this case, p2is the probability of receiving two uninfected units (0.81); 2pq is the probability of receivingone uninfected unit and one infectedunit (0.18); and q2 is the probability of receiving two infected units (0.01). This same process can be repeated with the binomial raised to the nth power, with n being the number of units transfused: (p + q)n = I. From this, the probability of an uninfected transfusion is p", a function of the number of donor exposures and the chance of receiving blood from an uninfected donor. Conversely,the probability of recipient exposure to an infectious agent can be calculated by 1 - p".
The formula 1 - pn is used to generate the data that appear in Table I. This table permits the reader to rapidly determine the risk of exposure to any transfusion-transmitted agent based on the prevalence of the agent in the tested blood supply and the number of transfusions administered. Note that when the prevalence is low, the
Volume 100
Informed consent, risk, and blood transfusion
Number 1 July 1990
89
Table I. Chance of exposure to transfusion-transmitted agents (percent) No. of exposures 0 1 2 3 4 5 6 7 8 9 10 15 20 25 50 100
Prevalence of undetected infected unit in blood supply 1:100.000
1:50.000
1:10.000
1:1.000
1:100
1:20
1:10
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.015 0.020 0.025 0.050 0.100
0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.030 0.040 0.050 0.100 0.200
0.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.49 1.98 2.47 4.88 9.52
0.00 1.00 1.99 2.97 3.94 4.90 5.85 6.79 7.73 8.65 9.56 13.99 18.21 22.22 39.50 63.40
0.00 5.00 9.75 14.26 18.55 22.62 26.49 30.17 33.66 36.98 40.13 53.67 64.15 72.26 92.31 99.41
0.00 10.00 19.00 27.10 34.39 40.95 46.86 52.17 56.95 61.26 65.13 79.41 87.84 92.82 99.48 99.99
om
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.15 0.20 0.25 0.50 1.00
probability of being exposed to the infectious agent can be estimated by multiplying the number of donor exposures by the prevalence of the agent in the blood supply. For example, if w.e assume a prevalence of an agent in the blood supply as 1:100,000 (0.001 %), then the risk of being exposed to this agent from one, two, or three blood transfusions is approximately 0.001%, 0.002%, and 0.003%, respectively. However, with increasing prevalence, the formula 1 - p" is used, although an alternative probabilistic approach has also been reported.' Discussion An understanding of the probability of exposure to transfusion-transmitted agents permits the physician to more adequately evaluate the risks of homologous transfusion versus the risks of autologous donation/transfusion, intraoperative blood salvage, and no transfusion. The risk of exposure becomes appreciable for patients with bone marrow failure as a result ofleukemia, aplastic anemia, or chemotherapy because these patients require large numbers of platelet concentrates and units of red blood cells. For example, the risk of exposure to a unit of blood contaminated by the human immunodeficiency virus (HIV) after appropriate laboratory testing (falsenegative laboratory result) has been estimated at 1:50,000.4 -6 However, with exposure to approximately 10 donors, there is a 1 in 5000 chance of exposure to HIV. The assumption that the prevalence of HIV in the tested blood supply approximates 1 in 50,000 was recently confirmed by Cohen and colleagues7 in a study involving patients undergoing cardiac surgery. Between April 1985
and December 1988, 36,282 units of blood components were transfused to 3400 patients undergoing cardiac surgery; one patient experienced seroconversion to HIV. The average patient had 10.7 donor exposures. The study concluded that the risk of transmission of HIV by transfusion was 0.003% per donor exposure. As additional or more specific testing is available that reduces the probability of exposure to transfusion-transmitted agents, the potential benefit to patients can be recognized. The most recent edition of the Standards for Blood Banks and Transfusion Services' requires blood banks to perform testing for alanine aminotransferase and hepatitis B core antibody on all blood donations. Because there is no specific test to detect non-A, non- B hepatitis, these two laboratory tests act as surrogate markers. It has been suggested that the addition of testing for alanine aminotransferase and hepatitis B core antibody will significantly reduce the probability oftransfusion-associated hepatitis by almost 50%.9 In addition, it is anticipated that the Food and Drug Administration will approve a specific test for hepatitis C during 1990. An example of clinical practice in which proper blood management demands close scrutiny is elective cardiac surgery. Information presented at an Autologous Transfusion Workshop (American Association of Blood Banks, Redondo Beach, Calif., 1988) demonstrated that transfusion methods during elective cardiac surgery vary considerably throughout the country. Some areas report the use of platelet transfusion in 25% to 50% of patients undergoing cardiac surgery. When such patients receive platelets, the product is usually administered in groups of
The Journal of Thoracic and Cardiovascular Surgery
9 0 Kolins and Kolins
Table II. Risk of accidental death compared with number of transfusions necessary to give an equivalent risk of HIV transfusion exposure* Cause of death
Accidental risk]
Motor vehicle accident Work accident Homicide Home accident Drowning Fire Airplane accident
0.02% 0.01% 0.009% 0.008% 0.002% 0.002% 0.0006%
Equivalent donor exposure risk 10
5 5 4 I
1 Less than I
'Assumes one undetected HIV-positive unit per 50.000 units tested."? tSource: Statistical Abstract of the United States. 107th cd. 1987.
sixor eightconcentratesat a time. Consequently thistype of practice results in exposure of these patients to large numbers of potentially infectious donors. Giordano and co-workers!" reported that the average number of exposures to homologous blood for cardiac surgery is 24 units when intraoperativeautologous transfusion is not used. However, the use of this technique reduced homologous blood exposures to 14 units per case. The beneficial effectof decreasing donorexposures by 10 is readily apparent by examination of Table I. The decrease in the chance of exposure to the non-A, non-B hepatitisagent whenexposed to 15units insteadof 25 depends on the prevalence of the agent in the tested blood supply. The decreasein thechanceofexposure dropsfrom 72% to 54% and from 22% to 14% when the prevalence of the agent in the bloodsupplyis 1:20 and 1:100,respectively. Should additionaltestingproveto reducethe prevalenceof the non-A,non-B hepatitisagent to 1:1000, then the decreasein the chanceof exposure to the non-A,nonB hepatitis agent wouldfall from 2.5% to 1.5% whenthe patient is exposed to 15 units instead of 25. Obviously, excessive transfusion results in high probability of exposure to an infectious agent, and therefore guidelines for transfusion in patientsundergoing cardiac surgeryshould beexaminedcritically, and patientsshouldbeinformedof this risk. It is appreciated that the risk of exposure to an infectious agent may not necessarily correlate with the risk of disease. Obviously, exposure to a virus in a patient with protective antibody to that virus may not result in development of the associated disease. However, for a virus such as HIV, the modelis especially appropriate because a patient population immune to HIV has not been described. The risks of transfusion have led to recommendations for informed consent before transfusion. This position is
supportedbythe AmericanAssociation of Blood Banks 11 (AABB) and the Report of the Presidential Commission on the Human Immunodeficiency VirusEpidemic. J 2 The AABB requires written informed consent before blood donation.f Althoughthe AABBstandards7 do notaddress written informed consent before blood transfusion, a memorandum to AABB institutional members, dated July 10, 1986, recommends documented informed consent before nonemergent transfusions. Thecourts havegenerally recognized blood as a service (rather than a product) and have refused to invoke the doctrine of implied warranty and strict liability when transfusion-transmitted diseases could not be prevented by all known, reasonable means. However, a recentU.S. Court of Appeals decision in the District of Columbia supportedthe plaintiff'schallenge that liability may exist regarding an adverse effect of transfusion if informed consent was not obtained.':' Althoughcontroversial, written informed consentprovides the physician with additional protection in our litigiousenvironment. In some arenas of medicine, such as HIV testing, state legislatures, including Californiaand Michigan, havemandated informedconsent. HIV legislationin Michigan14 has mandated the use ofa state-designatedand distributedconsentform which, whensigned by the patient,doesnot permit litigation basedon lackof informed consent. Similar legislation for informed consent beforetransfusion can also provide for a uniformity of the consentprocess whileprotectingphysicians from a common avenue of liability. Perhapsthe mostimportantaspectof informed consent iscomprehension. Informinga patient of transfusion risks does not necessarily mean the patient understands these risks." Consequently, Table II has beendeveloped to enable the physician and patient to comparethe riskof variousaccidentaldeaths to the riskof beingexposed to HIV. In other words, the table compares the risk of death resultingfrom unavoidable eventsin our dailylives likeaccidentsat home,at work,and in our automobiles to that of beingexposed to an undetected, HIV-infected unit of blood in the bloodsupply. It is evident that the chance of accidental death at home, for example, is greater than the risk of being exposed to HIV from a singledonor exposure. To reach the equivalent riskofdeath causedbyan accidentat home within any year, 4 units of blood must be transfused; to reach the equivalent risk of death from a motor vehicle accident, a lO-unittransfusion is necessary. It is interesting to note that airplane travel is statistically safer than a homologous bloodtransfusion. Commonly accepted risks help the patient gain perspective on blood transfusion. For example, the risk of
Volume 100
Informed consent, risk, and blood transfusion
Number 1 July 1990
exposure to HIV from a blood transfusion is about one tenth the risk of death after an influenza infection (1:50,000 compared with 1:5000) and about the same as the risk of death as a result of complications of using birth control pills." With increasing pressure for educated, informed consent, this information should provide a rational approach for physicians and patients to discuss potential therapies.
I.
2.
3.
4.
5.
6.
REFERENCES Petz LD, Tomasulo PA. Red cell transfusion. In: Kolins J, McCarthy LJ, eds. Contemporary transfusion practice. Arlington, Virginia: American Association of Blood Banks, 1987:1. Koziol DE, Holland PV, Alling OW, et al. Antibody to hepatitis B core antigen as a paradoxical marker for nonA, non-B hepatitis agents in donated blood. Ann Intern Med 1986;104:488-95. Rebulla P, Baroni L, Bertolini F, et al. The risk of acquiring transfusion-transmissible infections. Vox Sang 1988; 55:186-7. Ward JW, Holmberg SO, Allen JR, et al. Transmission of human immunodeficiency virus (HIV) by blood transfusions screened as negative for HIV antibody. N Engl J Med 1988; 318:.473-8. Kleinman S, Secord K. Risk of human immunodeficiency virus (HIV) transmission by anti-HIV negative blood: estimates using the lookback methodology. Transfusion 1988;28:499-50 I. Kleinman S, Secord K, Doyle M. Demographic profile and
7.
8.
9.
10.
II. 12.
13.
14. 15. 16.
91
motivations for donation in donors who have seroconverted for HIV [Abstract]. Transfusion I988;28S:29S. Cohen NO, Munoz A, Reitz BA, et al. Transmission of retroviruses by the transfusion of screened blood in patients undergoing cardiac surgery. N Engl J Med 1989;320: 1172-6. Holland PV, ed. Standards for blood banks and transfusion services. 13th ed. Arlington, Virginia: American Association of Blood Banks, 1989:15. Holland PV. Informing the transfusion recipient. How much is enough? In: Smith OM, Carlson KB, eds. Current scientific/ethical dilemmas in blood banking. Arlington, Virginia: American Association of Blood Banks, 1987:21. Giordano GF, Goldman OS, Mammana RB, et al. Intraoperative autotransfusion in cardiac operations: effect on intraoperative and postoperative transfusion requirements. J THORAC CARDIOVASC SURG 1988;96:382-6. Barnes A. Transfusion practice in the private hospital. Arch Pathol Lab Med 1989;113:296-9. Report of the Presidential Commission on the Human Immunodeficiency Virus Epidemic, June 24, 1988. Washington, DC: Government Printing Office, 1988; GPO publication no. 0-214-701:QI.3. Kuzop Georgetown University, 663 F Supp 1048 (DOC 1987) aff'd in part, rev'd in part 851 F2d 437 (DC Cir 1988). Michigan Act No. 488, Public Acts of 1988. Ingelfinger FJ. Informed (but uneducated) consent. N Engl J Med 1972;287:465-6. Dinman BD. The reality and acceptance of a risk. JAMA 1980;244:1226-9.
THORAC CARDIOVASC SURG
1990;100:88-91
Informed consent, risk, and blood transfusion Informed consent for blood transfusion bas become a necessity in light of the known risks associated with this service. AU transfusion services should institute written informed consent that clearly defines the patient's options, including the use of homologous blood, autologous blood, and directed donations. The risk of transfusion with an infectious blood product is dependent on the number of donors per recipient and the prevalence of undetected, contaminated blood in the tested blood supply. The chance that an adverse transfusion will occur can be calculated by use of these variables. Comparative risks can be explained to patients, thereby providing an understanding of the transfusion risk of human immunodeficiency virus, the human T-cell leukemia virus, and the agent of non-A, non-B hepatitis (hepatitis C).
Jerry Kolins, MD, Escondido, Calif., and Mark D. Kolins, MD, Detroit, Mich.
An
estimated 12 million units of blood are collected and transfused to approximately 3 million patients annually in the United States.' Although there are numerous adverse effects of receiving a blood transfusion, the concern of transfusion-transmitted infectious agents has received considerable attention since the recognition of the acquired immunodeficiency syndrome (AIDS). Transfusion-associated AIDS is rare; nevertheless it is the most feared complication of blood transfusion because the disease is fatal. This has led to intense scrutiny of the safety of the nation's blood supply, with resurgent interest in transfusion-associated hepatitis because transfusion-associated non-A, non-B hepatitis (hepatitis C) is more common than transfusion-associated AIDS and often results in cirrhosis and death? The reexamination of transfusion risk has motivated physicians to provide more information about transfusion risk to intended recipients of blood products. A natural evolution of this process includes written informed consent for this service. To enhance the consent process, tables have been constructed based on mathematic modeling; these provide rapid reference for the risk of recipient
exposure to an undetected, infectious unit in the blood supply.
Fromthe Community Blood Bank of North County and The Palomar Pomerado Health System, Escondido, Calif., and Department of Pathology, Detroit Riverview Hospital, Detroit, Mich. Received for publication June 2, 1989. Accepted for publication Aug. 14, 1989. Address for reprints: Jerry Kolins, MD, Community Blood Bank of • North County, 660 East Grand Ave., Escondido, CA 92025. 12/1/16323
Results
88
Methods The risk of receiving a unit contaminated with an infectious agent is directly dependent on the number of transfusions a patient receives: The more transfusions, the greater the risk. Assuming a 10% prevalence of a transfusion-transmitted agent in the donor population, Probability of uninfecteddonor = p = 0.9 Probability of infected donor = q = 6:1 p+q=1 If a recipient is exposed to two donors, the recipient may receive anyone of the following: two uninfected units, one uninfected unit and one infected unit, or two infected units. Mathematically this is expressed by the formula (p + q)2 = 12. The product of this squared binomial is p2 + 2pq + q2 = I. In this case, p2is the probability of receiving two uninfected units (0.81); 2pq is the probability of receivingone uninfected unit and one infectedunit (0.18); and q2 is the probability of receiving two infected units (0.01). This same process can be repeated with the binomial raised to the nth power, with n being the number of units transfused: (p + q)n = I. From this, the probability of an uninfected transfusion is p", a function of the number of donor exposures and the chance of receiving blood from an uninfected donor. Conversely,the probability of recipient exposure to an infectious agent can be calculated by 1 - p".
The formula 1 - pn is used to generate the data that appear in Table I. This table permits the reader to rapidly determine the risk of exposure to any transfusion-transmitted agent based on the prevalence of the agent in the tested blood supply and the number of transfusions administered. Note that when the prevalence is low, the
Volume 100
Informed consent, risk, and blood transfusion
Number 1 July 1990
89
Table I. Chance of exposure to transfusion-transmitted agents (percent) No. of exposures 0 1 2 3 4 5 6 7 8 9 10 15 20 25 50 100
Prevalence of undetected infected unit in blood supply 1:100.000
1:50.000
1:10.000
1:1.000
1:100
1:20
1:10
0.000 0.001 0.002 0.003 0.004 0.005 0.006 0.007 0.008 0.009 0.010 0.015 0.020 0.025 0.050 0.100
0.000 0.002 0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.030 0.040 0.050 0.100 0.200
0.00
0.00 0.10 0.20 0.30 0.40 0.50 0.60 0.70 0.80 0.90 1.00 1.49 1.98 2.47 4.88 9.52
0.00 1.00 1.99 2.97 3.94 4.90 5.85 6.79 7.73 8.65 9.56 13.99 18.21 22.22 39.50 63.40
0.00 5.00 9.75 14.26 18.55 22.62 26.49 30.17 33.66 36.98 40.13 53.67 64.15 72.26 92.31 99.41
0.00 10.00 19.00 27.10 34.39 40.95 46.86 52.17 56.95 61.26 65.13 79.41 87.84 92.82 99.48 99.99
om
0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 0.15 0.20 0.25 0.50 1.00
probability of being exposed to the infectious agent can be estimated by multiplying the number of donor exposures by the prevalence of the agent in the blood supply. For example, if w.e assume a prevalence of an agent in the blood supply as 1:100,000 (0.001 %), then the risk of being exposed to this agent from one, two, or three blood transfusions is approximately 0.001%, 0.002%, and 0.003%, respectively. However, with increasing prevalence, the formula 1 - p" is used, although an alternative probabilistic approach has also been reported.' Discussion An understanding of the probability of exposure to transfusion-transmitted agents permits the physician to more adequately evaluate the risks of homologous transfusion versus the risks of autologous donation/transfusion, intraoperative blood salvage, and no transfusion. The risk of exposure becomes appreciable for patients with bone marrow failure as a result ofleukemia, aplastic anemia, or chemotherapy because these patients require large numbers of platelet concentrates and units of red blood cells. For example, the risk of exposure to a unit of blood contaminated by the human immunodeficiency virus (HIV) after appropriate laboratory testing (falsenegative laboratory result) has been estimated at 1:50,000.4 -6 However, with exposure to approximately 10 donors, there is a 1 in 5000 chance of exposure to HIV. The assumption that the prevalence of HIV in the tested blood supply approximates 1 in 50,000 was recently confirmed by Cohen and colleagues7 in a study involving patients undergoing cardiac surgery. Between April 1985
and December 1988, 36,282 units of blood components were transfused to 3400 patients undergoing cardiac surgery; one patient experienced seroconversion to HIV. The average patient had 10.7 donor exposures. The study concluded that the risk of transmission of HIV by transfusion was 0.003% per donor exposure. As additional or more specific testing is available that reduces the probability of exposure to transfusion-transmitted agents, the potential benefit to patients can be recognized. The most recent edition of the Standards for Blood Banks and Transfusion Services' requires blood banks to perform testing for alanine aminotransferase and hepatitis B core antibody on all blood donations. Because there is no specific test to detect non-A, non- B hepatitis, these two laboratory tests act as surrogate markers. It has been suggested that the addition of testing for alanine aminotransferase and hepatitis B core antibody will significantly reduce the probability oftransfusion-associated hepatitis by almost 50%.9 In addition, it is anticipated that the Food and Drug Administration will approve a specific test for hepatitis C during 1990. An example of clinical practice in which proper blood management demands close scrutiny is elective cardiac surgery. Information presented at an Autologous Transfusion Workshop (American Association of Blood Banks, Redondo Beach, Calif., 1988) demonstrated that transfusion methods during elective cardiac surgery vary considerably throughout the country. Some areas report the use of platelet transfusion in 25% to 50% of patients undergoing cardiac surgery. When such patients receive platelets, the product is usually administered in groups of
The Journal of Thoracic and Cardiovascular Surgery
9 0 Kolins and Kolins
Table II. Risk of accidental death compared with number of transfusions necessary to give an equivalent risk of HIV transfusion exposure* Cause of death
Accidental risk]
Motor vehicle accident Work accident Homicide Home accident Drowning Fire Airplane accident
0.02% 0.01% 0.009% 0.008% 0.002% 0.002% 0.0006%
Equivalent donor exposure risk 10
5 5 4 I
1 Less than I
'Assumes one undetected HIV-positive unit per 50.000 units tested."? tSource: Statistical Abstract of the United States. 107th cd. 1987.
sixor eightconcentratesat a time. Consequently thistype of practice results in exposure of these patients to large numbers of potentially infectious donors. Giordano and co-workers!" reported that the average number of exposures to homologous blood for cardiac surgery is 24 units when intraoperativeautologous transfusion is not used. However, the use of this technique reduced homologous blood exposures to 14 units per case. The beneficial effectof decreasing donorexposures by 10 is readily apparent by examination of Table I. The decrease in the chance of exposure to the non-A, non-B hepatitisagent whenexposed to 15units insteadof 25 depends on the prevalence of the agent in the tested blood supply. The decreasein thechanceofexposure dropsfrom 72% to 54% and from 22% to 14% when the prevalence of the agent in the bloodsupplyis 1:20 and 1:100,respectively. Should additionaltestingproveto reducethe prevalenceof the non-A,non-B hepatitisagent to 1:1000, then the decreasein the chanceof exposure to the non-A,nonB hepatitis agent wouldfall from 2.5% to 1.5% whenthe patient is exposed to 15 units instead of 25. Obviously, excessive transfusion results in high probability of exposure to an infectious agent, and therefore guidelines for transfusion in patientsundergoing cardiac surgeryshould beexaminedcritically, and patientsshouldbeinformedof this risk. It is appreciated that the risk of exposure to an infectious agent may not necessarily correlate with the risk of disease. Obviously, exposure to a virus in a patient with protective antibody to that virus may not result in development of the associated disease. However, for a virus such as HIV, the modelis especially appropriate because a patient population immune to HIV has not been described. The risks of transfusion have led to recommendations for informed consent before transfusion. This position is
supportedbythe AmericanAssociation of Blood Banks 11 (AABB) and the Report of the Presidential Commission on the Human Immunodeficiency VirusEpidemic. J 2 The AABB requires written informed consent before blood donation.f Althoughthe AABBstandards7 do notaddress written informed consent before blood transfusion, a memorandum to AABB institutional members, dated July 10, 1986, recommends documented informed consent before nonemergent transfusions. Thecourts havegenerally recognized blood as a service (rather than a product) and have refused to invoke the doctrine of implied warranty and strict liability when transfusion-transmitted diseases could not be prevented by all known, reasonable means. However, a recentU.S. Court of Appeals decision in the District of Columbia supportedthe plaintiff'schallenge that liability may exist regarding an adverse effect of transfusion if informed consent was not obtained.':' Althoughcontroversial, written informed consentprovides the physician with additional protection in our litigiousenvironment. In some arenas of medicine, such as HIV testing, state legislatures, including Californiaand Michigan, havemandated informedconsent. HIV legislationin Michigan14 has mandated the use ofa state-designatedand distributedconsentform which, whensigned by the patient,doesnot permit litigation basedon lackof informed consent. Similar legislation for informed consent beforetransfusion can also provide for a uniformity of the consentprocess whileprotectingphysicians from a common avenue of liability. Perhapsthe mostimportantaspectof informed consent iscomprehension. Informinga patient of transfusion risks does not necessarily mean the patient understands these risks." Consequently, Table II has beendeveloped to enable the physician and patient to comparethe riskof variousaccidentaldeaths to the riskof beingexposed to HIV. In other words, the table compares the risk of death resultingfrom unavoidable eventsin our dailylives likeaccidentsat home,at work,and in our automobiles to that of beingexposed to an undetected, HIV-infected unit of blood in the bloodsupply. It is evident that the chance of accidental death at home, for example, is greater than the risk of being exposed to HIV from a singledonor exposure. To reach the equivalent riskofdeath causedbyan accidentat home within any year, 4 units of blood must be transfused; to reach the equivalent risk of death from a motor vehicle accident, a lO-unittransfusion is necessary. It is interesting to note that airplane travel is statistically safer than a homologous bloodtransfusion. Commonly accepted risks help the patient gain perspective on blood transfusion. For example, the risk of
Volume 100
Informed consent, risk, and blood transfusion
Number 1 July 1990
exposure to HIV from a blood transfusion is about one tenth the risk of death after an influenza infection (1:50,000 compared with 1:5000) and about the same as the risk of death as a result of complications of using birth control pills." With increasing pressure for educated, informed consent, this information should provide a rational approach for physicians and patients to discuss potential therapies.
I.
2.
3.
4.
5.
6.
REFERENCES Petz LD, Tomasulo PA. Red cell transfusion. In: Kolins J, McCarthy LJ, eds. Contemporary transfusion practice. Arlington, Virginia: American Association of Blood Banks, 1987:1. Koziol DE, Holland PV, Alling OW, et al. Antibody to hepatitis B core antigen as a paradoxical marker for nonA, non-B hepatitis agents in donated blood. Ann Intern Med 1986;104:488-95. Rebulla P, Baroni L, Bertolini F, et al. The risk of acquiring transfusion-transmissible infections. Vox Sang 1988; 55:186-7. Ward JW, Holmberg SO, Allen JR, et al. Transmission of human immunodeficiency virus (HIV) by blood transfusions screened as negative for HIV antibody. N Engl J Med 1988; 318:.473-8. Kleinman S, Secord K. Risk of human immunodeficiency virus (HIV) transmission by anti-HIV negative blood: estimates using the lookback methodology. Transfusion 1988;28:499-50 I. Kleinman S, Secord K, Doyle M. Demographic profile and
7.
8.
9.
10.
II. 12.
13.
14. 15. 16.
91
motivations for donation in donors who have seroconverted for HIV [Abstract]. Transfusion I988;28S:29S. Cohen NO, Munoz A, Reitz BA, et al. Transmission of retroviruses by the transfusion of screened blood in patients undergoing cardiac surgery. N Engl J Med 1989;320: 1172-6. Holland PV, ed. Standards for blood banks and transfusion services. 13th ed. Arlington, Virginia: American Association of Blood Banks, 1989:15. Holland PV. Informing the transfusion recipient. How much is enough? In: Smith OM, Carlson KB, eds. Current scientific/ethical dilemmas in blood banking. Arlington, Virginia: American Association of Blood Banks, 1987:21. Giordano GF, Goldman OS, Mammana RB, et al. Intraoperative autotransfusion in cardiac operations: effect on intraoperative and postoperative transfusion requirements. J THORAC CARDIOVASC SURG 1988;96:382-6. Barnes A. Transfusion practice in the private hospital. Arch Pathol Lab Med 1989;113:296-9. Report of the Presidential Commission on the Human Immunodeficiency Virus Epidemic, June 24, 1988. Washington, DC: Government Printing Office, 1988; GPO publication no. 0-214-701:QI.3. Kuzop Georgetown University, 663 F Supp 1048 (DOC 1987) aff'd in part, rev'd in part 851 F2d 437 (DC Cir 1988). Michigan Act No. 488, Public Acts of 1988. Ingelfinger FJ. Informed (but uneducated) consent. N Engl J Med 1972;287:465-6. Dinman BD. The reality and acceptance of a risk. JAMA 1980;244:1226-9.