Infections and Organ Transplantation
2012; Wolters Kluwer; Volume: 93; Issue: Supplement 5S Linguagem: Inglês
10.1097/tp.0b013e3182481347
ISSN1534-6080
AutoresPaolo Grossi, Alessandro Nanni Costa, Deirdre Fehily, Emily A. Blumberg, Matthew J. Kuehnert, Jay A. Fishman, Michael G. Ison, R. Lattes, Camille N. Kotton, Daniele Lilleri, Anna Kabanova, Antonio Lanzavecchia, Giuseppe Gerna, Raymund R. Razonable, Patrizia Comoli, Marco Zecca, Sabrina Basso, Fabrizio Ginevri, A. Grossi, Francesco Paolo Schena, Antoni Rimola, Patrizia Burra, Elenora De Martin, K. Rodriguez-Castro, S. Fagiuoli, L. Pasulo, Raffaele Bruno, Pietro Andreoné, Elisabetta Loggi, Fabio Arena, Gian María Rossolini, Gabriele Sganga, Valerio Cozza,
Tópico(s)Organ Donation and Transplantation
ResumoSECTION 1: ORGAN, TISSUE, AND CELL VIGILANCE IN ITALY Alessandro Nanni Costa, and Deirdre Fehily As the regulation of organ, tissue, and cell donation and transplantation has developed in the European Union, the Italian Transplant Network, coordinated by National Transplant Centre (CNT), has led the implementation of the legislative requirements in Italy, focusing efforts on ensuring safety from the moment of donor identification to the clinical follow-up of recipients. The European legal framework covers substances of human origin and comprises a series of Directives, the most recent of which defines the requirements for organ donation and transplantation (Figure 1).FIGURE 1: The development of EU Regulation of substances of human origin.Vigilance is a fundamental element identified in all of these Directives, with a requirement for the notification of serious adverse events (SAEs) and reactions (SARs). Safety and Risk in Organ Transplantation All types of transplantation imply inherent risks that must be minimized through the application of stringent safety procedures. In the case of organ transplantation particularly, the associated risks must be weighed against the benefits of receiving a transplant in the context of organ shortage. Italian transplantation guidelines identify five levels of risk: Unacceptable risk An increased but acceptable risk Calculated risk Non-assessable risk or potentially high risk for infectious disease transmission Standard risk An example of risk level 4 would be a case where during 2 weeks before donation, the donor had participated in high-risk behavior for infectious disease transmission (e.g., prostitution or drug injection), the possible positivity for which might not be detected even through the most sensitive techniques of molecular biology are applied. Only those potential recipients who signed a specific consent form when they were entered on the waiting list can receive organs categorized with this risk level. Although the Italian guidelines are now well established, each case is different and individual decisions are frequently required to ensure that valuable organs are not lost and recipients are not exposed to unjustifiable risk. This process is supported by a system of "Second Opinion" for evaluation of risk. A 24 hr a day, 7 days a week support is provided by a team of specialists in infectious disease, pathology, legal medicine, intensive therapy and immunological disease. Two National Coordinators are available for a second opinion on organ suitability and therapeutic suggestions for donors or recipients. In the case of donor malignancies, considerable improvements have been achieved in detection before transplantation (Figure 2). All the centers transplanting organs from infected or neoplastic donors are asked to supply regular follow-up data to the National Centre for Transplantation, so that the implications of transplanting organs with elevated risk are closely monitored.FIGURE 2: Timing of neoplasia identification.Table 1 shows the donations classified as involving "Calculated Risk" and demonstrates the value, in terms of effective transplants, of applying this approach to donor selection.TABLE 1: Transplants with calculated risk 2003–2010Risk reduction and management requires continual reevaluation of changing and emerging risk. In Italy, the arrival of West Nile Virus required additional monitoring and the application of safety measures to reduce any risk of transmission by transplantation (1). Retrospective screening of organ donors in 2009 provided valuable information regarding the spread of West Nile Virus (2). Vigilance However, despite the application of safety guidelines and the establishment of advisory networks, mistakes can happen and unexpected transmissions occur. The most important serious adverse reaction (SAR) in the field of organ transplantation in Italy in recent years was the transmission of HIV to three organ recipients after a transcription error in a testing laboratory (3). The incident resulted in a thorough review of the safety system, the establishment of a National Safety Audit Commission and a survey and audit program of testing laboratories. When tragic incidents of this type occur, it is essential that the outcomes and lessons learned be effectively communicated to all those involved in the network, so that appropriate measures can be taken to prevent recurrence. Since February 2007, CNT has been collecting information regarding all SARs and SAEs occurring nationally within the transplant network, applying the definitions used in the European Directives ("serious adverse event" means any untoward occurrence associated with the procurement, testing, processing, storage, and distribution of tissues and cells that might lead to the transmission of a communicable disease, to death or life-threatening, disabling, or incapacitating conditions for patients or which might result in, or prolong, hospitalization or morbidity. "Serious adverse reaction" means an unintended response, including a communicable disease, in the donor or in the recipient associated with the procurement or human application of tissues and cells that is fatal, life-threatening, disabling, incapacitating or which results in, or prolongs, hospitalization or morbidity). A national reporting form was adopted in May 2010, which is submitted together with a detailed report for each notification. Adverse events, where no patient has been harmed but an incident has occurred which implied or still implies risk, are considered important within the Italian system where they allow the sharing of information for the prevention of harm. Reports indicate that serious adverse reactions or events (SARE) occur at all stages of the process from donation to transplantation (Figure 3).FIGURE 3: Reports of Serious Adverse Events and Reactions in the field of Transplantation in Italy.European Union funded projects, particularly EUSTITE (European Union Standards and Training for the Inspection of Tissues Establishments) and EFRETOS (European Framework for the Evaluation of Organ Transplants) have developed important principles of good practice and standard evaluation tools to support vigilance. These have been incorporated in the Italian system where they support the process of severity evaluation, assessment of imputability, and the broader impact of any particular SAR or SAE. The importance of vigilance communication is recognized by the inclusion of a forum for the discussion of adverse events and reactions on a social networking site restricted to the Italian Transplant Network. The Italian experience demonstrates that the identification, analysis, and communication of negative outcomes in transplantation are essential tools for ensuring continuous improvement and an ever-reducing level of risk for donors and recipients. 1. Nanni Costa A, Grossi P, Porta E, et al.. Measures taken to reduce the risk of West Nile virus transmission by transplantation in Italy. Euro Surveill 2008; 13: 16. 2. Capobianchi MR, Sambri V, Castilletti C, et al..; on behalf of the Italian Transplant Network. Retrospective screening of solid organ donors in Italy, 2009, reveals unpredicted circulation of West Nile virus. Euro Surveill 2010; 15: pii: 19648. 3. Villa E, Nanni Costa A. HIV-positive organs used for transplant in Italy due to human error. Euro Surveill 2007; 12: E070308. SECTION 2: VIGILANCE AND SURVEILLANCE OF DISEASE TRANSMISSION: THE OPTN AD HOC DISEASE TRANSMISSION ADVISORY COMMITTEE EXPERIENCE Emily A. Blumberg Donor-transmitted diseases, especially infections and malignancies, have been a focus of posttransplant surveillance in the United States. Identifying donor-derived events has required an integrated approach, involving transplant centers, organ procurement organizations, and the Organ Procurement and Transplantation Network (OPTN). Information gathered from review of potential donor-derived transmission events has formed the basis for biovigilance efforts, expanding our understanding of factors involved in disease transmission. The structure for biovigilance in the United States was developed in conjunction with the institution of specific governmental laws and policies. These included the National Organ Transplant Act (NOTA) of 1984, which inter alia established the US OPTN and Organ Procurement Organization (OPO) system and requires standards to prevent the procurement and transplant of organs from donors infected with HIV (1). In 2000, the US Department of Health and Human Services issued the OPTN "Final Rule" further directing the OPTN to implement standards to prevent the acquisition of organs from donors infected with HIV, as outlined in Section 42 CFR 121.6(b) (2). These policies refer to US Public Health Service (PHS) guidelines for testing organ donors and following transplant recipients for the specific purpose of preventing infectious diseases and again noted that organs from individuals with HIV could not be used (3). In keeping with these mandates, the OPTN proceeded to develop policies to identify and track disease transmission events. In 2005, the OPTN implemented policy requiring reporting of all potential or proven transmissions of a medical condition, including infections and malignancies, discovered after procurement of a donor organ to the OPTN (4, 5). The Disease Transmission Advisory Group was formed to evaluate these reports of potential disease transmission. By 2008, this group had become the formalized OPTN Ad Hoc Disease Transmission Advisory Committee (DTAC), charged with evaluating the risk and association of specific reports of potential disease transmission. The committee is a multidisciplinary one, with membership that includes physicians specializing in infectious diseases, pathology, oncology, transplant surgery, and transplantation medicine (e.g., nephrology), as well as transplant nurses, administrators, and coordinators, organ procurement organization representatives, laboratory directors, and government representatives (Appendix A). The initial reports are submitted to the Improving Patient Safety portal of the OPTN computer system and then made available to all DTAC members in an identity blinded report through a password-protected SharePoint Server. The committee members may request additional information to determine attribution, and in some cases, public health authorities may become involved if the case involves a nationally notifiable disease (e.g., Hepatitis A, B, C, HIV, and diverse other transmissible infections) (6) or if specialized testing is required. OPTN staff ensures notification of other centers that may have potentially affected recipients as appropriate, and obtains follow-up to determine patient outcome at 45 days. On the basis of the case review, DTAC then determines the likelihood of the transmission event, categorizing events as proven, probable, possible, intervention without documented transmission, and unlikely/excluded (Table 2) (5). On the basis of the information gleaned from the case reviews, DTAC may develop policy modifications and guidance documents and has also shared learning points with the transplant community through presentations at meetings and publications in key medical journals and OPTN newsletters.TABLE 2: Probability of donor-derived eventReports to DTAC have increased over time (Fig. 4). However, despite mandated reporting, not all donor service areas and regions have been consistent with their reports; some areas have not reported any events during a specific year. Improving reporting to the patient safety system has become a recent focus of DTAC efforts. The majority of reports are related to potential infection transmission events; however, malignancies are also frequently reported (Table 3). The most common organisms reported due to potential infection transmissions were viral pathogens. Fungi and viruses were most commonly associated with transmission, and fungal and parasitic pathogens were proportionally more likely to result in proven and probable transmissions on a case-by-case basis. The most common malignancy reported to DTAC was renal cell carcinoma, but confirmed transmission events were more likely to occur when donors had lung cancer, lymphoma, or melanoma (Table 4).FIGURE 4: Number of Cases Reported to DTAC Annually.TABLE 3: Summary of reported cases: 2005–2010TABLE 4: Malignancy reports 2005–2010Estimates of the percentage of transplants resulting in transmission events in the United States have been confounded by probable underreporting of transmission events to the Improving Patient Safety portal. Consequently, it is not known exactly how many donors have transmitted infections or malignancies to recipients. Rough estimates based on 2009 reports suggest that approximately 0.4% of deceased donors resulted in a proven or probable transmission event. When live donors are also considered, underreporting remains an issue. Review of data from 2010 suggests that when live and deceased donor transplants are combined, given a total of 14,508 donors in the United States, at least 1 disease transmission occurred with approximately 0.2% of all donors (26 of 14,508) and impacted 0.1% of all transplants (37 of 28,662). This estimate was based on the report of 26 proven or probable transmission events in that year that resulted in 37 transmissions to individual recipients. Outcomes related to transmission events have been variable, and it has been difficult to definitively determine the incidence of death and graft loss in patients with donor-derived transmission events. Based on the reports to the OPTN in 2010, the mortality rate associated with proven and probable transmission events was 35.1% for recipients with a transmission and 15.9% (13 of 82) for all recipients in cases where the donor resulted in at least one proven or probable transmission. DTAC has reviewed key trends in transmission events and reporting systems. These have included events that have been more commonly associated with disease transmission and mechanisms for interrupting transmission by the use of prophylactic strategies. Testing modalities have also been evaluated. Several recent key observations are summarized as follows. Recently, there has been an increased use of nucleic acid testing (NAT) to identify donors with HIV, hepatitis C, and hepatitis B. This reflects the recognition of delayed identification of these infections in recently infected individuals because of the prolonged window period until seroconversion (7). A review of nucleic acid test results reported to the Improving Patient Safety portal was presented at the Infectious Diseases Society of America (8). This review reported that discordant results for HIV, hepatitis B, and hepatitis C accounted for 6.6% (20/302) of potential disease transmission reports to the Patient Safety System for 2008 to 2010. Of these, two donors had false-negative HBV serology without disease transmission and one donor had false-negative HCV serology with all three recipients contracting HCV; in this case, HCV was detected by NAT performed after the transplant as a part of tissue screening. Most of the other reports reflected non-reproducible positive NAT results performed for tissue donor assessments, which were conducted by a different laboratory than that used for organ donor testing. This raises concerns regarding the reliability of test results conducted by diverse laboratories for additional donor assessments. Bacterial transmission events have also been a concern. In an abstract presented at the Infectious Diseases Society of America in 2010, 11 donors transmitted bacterial infections to 22 of 42 recipients transplanted between 2006 and 2009 (9). Notably, the majority of infections were due to gram-negative bacilli; 5 of 11 donors had antibiotic resistant bacteria. One potential risk factor for transmission was direct organ soilage related to abdominal trauma. Adverse recipient outcomes were common with reports of mycotic aneurysm, allograft loss, and recipient deaths. Transmission was successfully averted in recipients who were given appropriate antibiotics. Consequently, as suggested by diverse reports, donors with bacterial infections may be used successfully if directly contaminated organs are not used and targeted prophylactic antimicrobials are administered to risk recipients (10, 11). Ongoing evaluation of potential donor-derived transmission by DTAC continues with increasing attention for improving the efficiency of the reporting system and greater recognition and reporting of potential donor-derived transmission events to the Improving Patient Safety portal. Current areas of investigation include determination of recipient outcomes in donors with undiagnosed central nervous system processes, improving recognition of geographically associated illnesses (such as strongyloidiasis and coccidioides) as the donor population becomes more heterogeneous, and improving our understanding of malignancy transmission events (12). A number of challenges continue to have a significant impact on the assessment of disease transmission related to organ transplantation in the United States. Optimal donor testing for a number of pathogens, including blood-borne viruses and tuberculosis, needs to be determined. This is especially important as the donor pool becomes more geographically diverse. The impact of blood donors on donor-derived transmissions is unknown; at least two organ donors acquired West Nile virus infection from a blood donor and subsequently transmitted this infection to all four recipients of this donor's organs with adverse results (13, 14). Hemodilution related to massive blood transfusion of donors may further affect the validity of donor testing; the impact of hemodilution on donor test results has not been fully characterized. It is also unclear how long recipients should be followed to exclude donor-derived transmission events; presumably donor-derived malignancies may require longer follow-up than donor-derived infections. With time, awareness of donor-derived transmission events has increased substantially in the United States. Increased reporting each year during the initial 5 years suggests improved compliance with the requirement for transplant centers and organ procurement organizations to report potential transmission events to the national reporting system administered by the OPTN. Review of these reports by a multidisciplinary team of transplant professionals has enhanced our understanding of risk factors associated with donor-derived transmission events. Ultimately this has led to an increased attention to biovigilance and donor safety, an ongoing process that should continue to result in improved transplant outcomes. ACKNOWLEDGMENTS The author thanks Michael Ison, M.D., M.S., Timothy Pruett, M.D., Shandie Covington, Sarah Taranto, Kimberly Taylor, R.N., and Kimberly Parker for their contributions. 1. http://uscode.house.gov/uscode-cgi/fastweb.exe?getdoc+uscview+t41t42+597+0++%28%29%20%20AND%20%28%2842%29%20ADJ%20USC%29%3ACITE%20AND%20%28USC%20w%2F10%20%28273%29%29%3ACITE%20%20%20%20%20%20%20%20%20http://www.gaonet.gov/special.pubs/organ/appendd.pdf. Accessed August 7, 2011. 2. http://ecfr.gpoaccess.gov/cgi/t/text/text-idx?c=ecfr&tpl=/ecfrbrowse/Title42/42cfr121_main_02.tpl. Accessed August 7, 2011. 3. Rogers MF, Simonds RJ, Lawton KE, et al.. Guidelines for preventing transmission of human immunodeficiency virus through transplantation of human tissues and organs. CDC MMWR Recommendations and Reports. 1994; 43(RR-8): 1. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/00031670.htm. 4. http://optn.transplant.hrsa.gov/policiesAndBylaws/policies.asp. Accessed August 7, 2011. 5. Ison MG, Hager J, Blumberg E, et al.. Donor-derived transmission events in the United States: Data reviewed by the OPTN/UNOS Disease Transmission Advisory Committee. Am J Transplant 2009; 9: 1929. 6. http://www.cdc.gov/osels/ph_surveillance/nndss/phs/infdis2011.htm. Accessed August 7, 2011. 7. Zou S, Dodd RY, Stramer SL, et al..; for the Tissue Safety Study Group. Probability of viremia with HBV, HCV, HIV and HTLV among tissue donors in the United States. N Engl J Med 2004; 351: 751. 8. Ison MG, Green M, Covington S, et al.. Discordant testing results—Lessons learned. A report from the OPTN Ad Hoc Diseases Transmission Advisory Committee (DTAC). Vancouver, Canada, Infectious Diseases Society of America 2010. Available at: http://idsa.confex.com/idsa/2010/webprogram/Paper3055.html. Accessed August 7, 2011. 9. Blumberg E, Green M, Covington S, et al.. Donor derived bacterial infections: Report from the Disease Transmission Advisory Committee (DTAC). Vancouver, Canada, Infectious Diseases Society of America 2010. http://idsa.confex.com/idsa/2010/webprogram/Paper3060.html. Accessed August 7, 2011. 10. Freeman RB, Giatras I, Falagas ME, et al.. Outcome of transplantation of organs procured from bacteremic donors. Transplantation 1999; 68: 1107. 11. Len O, Gavaldà J, Blanes M, et al.. Donor infection and transmission to the recipient of a solid allograft. Am J Transplant 2008; 8: 2420. 12. Nalesnik MA, Woodle ES, DiMaio JM, et al.. Donor-transmitted malignancies in organ transplantation: Assessment of clinical risk. 2011; 11: 1140. 13. Iwamoto M, Jernigan DB, Guasch A, et al.. Transmission of West Nile virus from an organ donor to four transplant recipients. N Engl J Med 2003; 348: 2196. 14. West Nile Virus transmission via organ transplantation and blood transfusion. Louisiana 2008. MMWR Morb Mortal Weekly Rep 2009; 58: 1263. SECTION 3: NUCLEIC ACID TESTING FOR ORGAN DONORS: WHAT IS THE RIGHT BALANCE BETWEEN SAFETY AND AVAILABILITY? Matthew J. Kuehnert This presentation will include a review of lessons learned from recent transmissions through organ transplantation, including HIV transmission from deceased and living donors; preliminary results of a study estimating the yield of nucleic acid amplification testing (NAT) for organ donor screening; identification of knowledge gaps in organ safety, highlighting the need for prospective data collection to improve risk estimates to gauge the effectiveness of current policies. The Office of Blood, Organ, and Other Tissue Safety coordinates investigations, surveillance, research, policy, and communications within Centers for Disease Control and Prevention (CDC), and collaborates with other institutions in the United States and globally, concerning issues of transfusion and transplantation safety. Given the lack of a formal public health surveillance system for organ transplant-transmitted disease transmission in the United States (as exists for transfusion-related adverse events, including disease transmission), CDC relies on public health investigations to gather data to recognize gaps in patient safety. Since HIV was first recognized to be transmitted through organ transplantation in the 1980s, a widening array of viruses (e.g., HIV, Hepatitis C virus, West Nile virus, rabies), bacteria (e.g., multidrug-resistant Escherichia coli, Mycobacterium tuberculosis), fungi (e.g., zygomycosis, coccidioidomycosis), and parasites (e.g., Trypanosoma cruzi, Babesia microti) (1, 2) have also been implicated in transmission. Of note, the first transmission of a free-living ameba, Balamuthia mandrillaris, was recently recognized in two separate clusters, each resulting from a donor with undiagnosed encephalitis (3, 4). Another cause of disease transmission from donors with encephalitis in multiple clusters, with devastating consequences, is lymphocytic choriomeningitis virus (5). Of pathogens that are screened for routinely, HIV and hepatitis viruses are of greatest concern for unrecognized donor transmission. In 2007, CDC assisted in an investigation in which both HIV and HCV were transmitted from a donor to four organ transplant recipients (6). This cotransmission had never been recognized before then and resulted in the death of two patients, with the remaining two patients suffering graft loss. The deceased donor, who was known on initial evaluation to be at elevated risk for HIV infection, was screened with serology as is standard by OPOs, and tested negative for presence of HIV and HCV antibody, but retrospectively was found to be viremic with HIV and HCV, as indicated by positive NAT on serum obtained at the time of organ recovery. Prospective donor screening with HIV and HCV NAT likely would have prevented this tragic event and should be carefully considered. In 2009, HIV was transmitted to a kidney recipient from a living donor (7). After the recipient developed an opportunistic infection and was found to have HIV, the donor was also diagnosed with HIV, and an investigation was initiated. On initial evaluation, the donor was known to be at high risk due to sexual behavior (i.e., men who have sex with men [MSM]), and HIV serology performed 79 days before organ removal was negative. On investigation, NAT was positive in the donor 11 days before transplant and in the recipient 12 days posttransplant, with donor and recipient viral sequences being 98% identical. As part of this report, CDC now recommends NAT for living donor screening no more than 7 days before organ removal. Appropriate donor education and recipient informed consent also is critical. CDC recommendations, although taken seriously by the US transplant community, must be adopted by the OPTN to become mandatory policy and can result in a gap between oversight and public health. For instance, at the time of this colloquium, there is no national policy for screening of living donors. A past survey also has shown that few recipients who receive organs from high-risk donors are tested for HIV posttransplantation to increase recognition of transmission, despite recommendations to do so in the 1994 Public Health Service (PHS) Guidelines (8). Therefore, given the lack of surveillance and posttransplant recipient testing, it is highly unlikely that there have been only two HIV transplant transmissions since 1987, as is sometimes alleged on a basis of a literature review, as some likely go unrecognized or unreported to public health. There is much to learn from these events, and this is why it is critical to improve surveillance on adverse events and process incidents in organ transplantation, both in the United States and globally (9, 10). In the absence of data, models must be used to estimate the risk of transmission given current screening and the potential benefit of additional screening. Although there is OPTN policy for screening deceased donors for infectious pathogens, there is no standard for use of NAT in donor screening. In a recent survey, the majority of US OPOs do not use NAT routinely for HIV, HBV, and HCV in donor screening. We collaborated with 17 OPOs, representing over half of the potential organ donor supply, to estimate the residual risk of HIV and HCV transmission using serology alone, and the additional reduction of risk added by the use of NAT (11). The estimate was done by measuring prevalence in potential organ donors, then imputing incidence from blood donor data, and finally using test window periods to estimate residual risk. For HIV, prevalence was 0.2% (0.1%, 0.5%, and 1.0% for normal, high, and missing risk, respectively); when NAT was added to serology, residual risk for HIV was reduced from 1 in 60,000 to 1 in 180,000 for normal risk, and from 1 in 12,000 to 1 in 36,000 for high risk. For HCV, prevalence was 5.6% (3.5%, 18.2%, and 12.9% for normal, high, and missing risk, respectively); when NAT was added to serology, residual risk was reduced from 1 in 5,000 to 1 in 50,000 for normal risk and from 1 in 1,000 to 1 in 10,000 for high risk. From these estimates, there is approximately one HIV-positive infected donor that is undetected every 3 years, and approximately two to three HCV-positive donors undetected every year, presumably many of which are unrecognized. When comparing the residual risk of HIV and HCV of blood, tissue, and organ donors, it is evident that high-risk organ donors are more than 100 times more likely to transmit HIV than blood donors, and more than 1,000 times more likely to transmit HCV. In conclusion, these results suggest that NAT screening versus serologic screening alone could substantially reduce the chances of undetected HIV and HCV infection among potential organ donors and thus improve patient outcomes, make organ placement more efficient, and clarify recipient informed consent. The US transplant community opinions on the role of NAT in routine organ donor screening is diverse. A consensus conference report endorsed by AST and ASTS independent of the US federal government did not find sufficient evidence to recommend routine NAT for HIV, HBV, and HCV as the standard of care for the screening of potential organ donors (12). For increased risk donors, however, the report authors believed that NAT should be considered to reduce the risk of transmission and potentially increase organ utilization, with the highest yield likely for HCV infection. Although false-positive rates are unpublished and could not be cited in this article, risk-benefit models were created based on assumption of false-positive rates of 0.1%, 0.02%, and 0.01%, showing loss of quality-adjusted life years (QALY) for all estimates when NAT was used for all donors. However, there were a number of weaknesses in this analysis. First, it is unlikely that false positives are more frequent than 1 in 10,000
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