Advancing Prion Science Guidance for the National Prion Research Program (2004) / Chapter Skim
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5 Testing Blood for Evidence of Agents of Transmissible Spongiform Encephalopathies
5 Testing Blood for Evidence of Agents of Transmissible Spongiform Encephalopathies
Pages 108-124
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From page 108... ...
This theoretical risk has several implications and justifies an intense search to develop laboratory tests that can detect prions in blood. One implication is that a blood test might allow earlier diagnosis and treatment for persons infected with a TSE agent.
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From page 109... ...
infected recipient guinea pigs by the intracerebral, subcutaneous, intramuscular, and intraperatoneal routes (Manuelidis, 19781. And the BSE agent, an acknowIedged TSE agent that can infect humans, was shown to transmit infectivity to 4 of 48 mouse recipients when pooled plasma, obtained from blood collected by heart puncture of 55 TSE-affected donor mice, was injected intracerebrally into these recipients (Taylor et a.l, 20001.
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From page 110... ...
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From page 111... ...
Hunter's team reported that 2 of 24 recipient sheep transfused with blood from BSE-infected donor sheep and 4 of 21 recipient sheep transfused with blood from scrapie-infected donor sheep succumbed to the respective TSE agent. This number of transmissions could increase as the animals are followed for longer time periods.
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From page 112... ...
route. RISK OF HUMAN-TO-HUMAN TRANSMISSION OF TSE AGENTS BY TRANSFUSION AND TRANSPLANT Concern that human-to-human transmission of prions could occur through blood products has been based, in part, on the knowledge that human TSEs have been documented to result from the administration of other human tissues or by contaminated instrumentation.
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From page 113... ...
Type of Study Study Question Yes No Clinical case reports Can the infectious agent of a TSE be transmitted from infected human tissues by injection or transplantation? aura mater transplants X corneal transplants X human pituitary hormone gonadotropin reuse of surgical instruments contaminated by prions blood productsa Epidemiological studies X X X surveillances Is there an increase in the number of CJD cases commensurate with the increased use of blood transfusions ?
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From page 114... ...
BLOOD TESTS FOR TSE AGENTS Sensitivity and Specificity Given the theoretical risks for transmissibility of prions in blood or blood products, the perceived need for a reliable screening blood test is apparent. Absent such a test to clear persons exposed to the agent associated with vCJD, donor deferral, based on geographic history, will remain in
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From page 115... ...
Recently, information gained from compartmentalized infectivity studies in a mouse mode! and a complex series of mathematical calculations helped an investigator determine that 100 IU of infectivity (in huffy coat)
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From page 116... ...
Reporting Results and Counseling Donors Who Test Positive for TSE There are additional concerns related to proper counseling and reporting of TSE screening tests. Most of these concerns focus on management of consent for use of the test and notification of the test result.
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From page 117... ...
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From page 118... ...
. Unfortunately, given the characteristics of TSEs and the absence of any organized prospective studies on populations at risk of developing a spontaneous or foodborne TSE, it is unlikely that there will be any meaningful quantitative or clinical information about the prognostic significance of a positive test result at initiation of testing.
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From page 119... ...
had clear and well-established risk factors; many if not most of those who were found to have a positive test result were not completely unprepared for the news. In contrast, those who received indeterminate results were greatly troubled, as they generally had no risk factors.
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From page 120... ...
If the commercial sector were to develop and market a candidate screening test for CTD, that test would first need to be the approved by the FDAa methodical and time-intensive process. The FDA uses a variety of pathways and governing legislative codes to evaluate and approve medical products.
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From page 122... ...
The biotechnology industry needs to be properly configured to successfully mass-produce a novel test product. Test users need to develop ethically sound counseling and notification policies, especially for those with a positive test result.
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From page 123... ...
2002. Animal models of bovine Spongiform encephalopathy and vCJD infectivity in blood: two swallows do not a summer make.
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From page 124... ...
Paper presented at Cambridge Healthtech Institute 6th Annual Meeting Blood Product Safety: TSE, Perception Versus Reality.
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