Blood and Blood Products Safety and Risk (1996) / Chapter Skim
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2: Guarding the Blood Supply
2: Guarding the Blood Supply
Pages 25-66
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II Guarding the Blood Supply
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The study will run from 1989 to 1998, and it is likely that it will be extended beyond then. The purpose is to monitor the safety of the nation's blood supply through studies of the epidemiology of known agents, essentially retroviruses, among volunteer blood donors.
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Serum taken from donors routinely is selected at random based on a complicated sampling methodology devised by the statisticians at Westat. Samples in the special repositories are: donations that are repeatedly reactive for HTLV, but for which confirmatory testing is unclear; donations from sex partners of HTLV-positive subjects and their controls; donations that were repeatably reactive for HIV- 1 but which produced indeterminate Western blots; donations that were repeatedly reactive for HIV-2 but HIV-1 negative; and donations that were repeatably reactive for HIV but of unclear etiology.
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The information in this database is immense and enormously valuable. To date, the surveys have found that more risky behavior is being encountered than predicted: up to 1 percent of people report prior drug use, sexual activity with a previous drug abuser, etc.
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These involved incidence data and window period estimates for viral diseases and how much we would close the window by antigen testing and whether there would be a magnet effect. REDS will continue to make general contributions to the risk literature.
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as well as the prevalence of infectious markers that has been observed. I would then like to share with you the attempts to estimate the incidence of infectious disease markers, how incidence differs Tom prevalence, and how the incidence rate can be used in conjunction with estimates of periods of true positivity but seronegativity (window periods)
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Suppose person A gives two seronegative donations 18 months apart, and person B gives two seronegative donations 6 month apart. Neither one is an incident case, so we could say the incidence rate is O out of 2 donors.
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The hepatitis B virus (HBV) incidence rate is based solely on the HBV surface antigen (HBsAg)
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To see what impact this can have, we can just assume a certain rate for first-time donors relative to that for repeat donors and weight that rate by the percentage of first-time donors in our study. For example, let us use the observed incidence rate of 2.61 per 100,000 person-years and say the window period is 45 days.
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This downward trend over time is what you would expect if you were decreasing the incidence rate (by effective donor screening) and/or decreasing the window period (by improved HIV tests)
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. Narrowing the window period with a third generation anti-HIV-1-2 enzyme immunoassay: relevance to P24 antigen screening of blood donors in the United States [abstract]
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We saw how the risk of donation during an infectious window period depends directly, proportionately, and equally on the incidence rate and the length of the window period and how the incidence rate can be used to assess the impact, or yield, or benefit of shortening the window period. I have used 5'See Schreiber et al.
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I think it will be interesting to see if the same demographic patterns that have been observed in the prevalence of infectious disease markers hold for the incidence rates. Finally, REDS will continue to monitor and report on changes with time, and will incorporate results from the other REDS components, such as the special donor surveys, as part of its mission to monitor the safety of the U.S.
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The blood centers in the interview study are not the same as those in the Red Cross study. The collaborative study with the American Red Cross collects information on approximately 2 million donations each year from 19 Red Cross regions.
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Analysis of the Red Cross data allowed us to evaluate the cost and effectiveness of syphilis testing as a surrogate marker for HIV window period donations. We have also used the Red Cross dataset to evaluate the effectiveness of the confidential unit exclusion system and more recently the risk of HIV transmission by screened blood in the United States.
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and other study groups to retest blood donations that had positive and indeterminate HIV Western blot results and negative EIA results with high optical density readings. Other special studies include collaborative look-back investigations to determine the length of the HIV infectious window period and the risk of HIV transmission by screened blood.
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Paul McCurdy: Many people in the audience know that in the late 1970's the National Heart, Lung and Blood Institute sponsored a transfusion transmitted virus study, the so-called TTV study. As part of that study a repository was established that has been used to look at prevention of hepatitis C virus transmission by antibody testing.
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For example, we routinely do analyses for Blood Products Advisory Committee meetings. Whenever an issue comes up, we are poised to respond with the appropriate dataset, and vice versa.
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44 BLOOD AND BLOOD PRODUCTS: SAFER AND RISK knew that there was a such a virus, and far more were infected before we had a test. You cannot really use these repositories until you have a test.
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The individual reports are collected in a central repository, whether it be at the local or state health department, the Centers for Disease Control and Prevention (CDC) , a blood collection center, or any other organization that may be collecting the information.
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There may be a clinical event or it may be subclinical, but we have good laboratory markers for many of the hepatitis types that are transfusion transmitted. The clinicians involved may report back
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The first thing that had to be done was to put together the clinical parameters and then the immunologic parameters. Over the first 3 to 6 months, CDC, health departments, and clinicians around the country did a superb job of assembling the basic epidemiologic parameters.
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For the known problems, it is important that we continue to publish information about current events and trends and to be certain that clinicians as well as health officials, blood banking officials, and federal government officials are all aware of that information. We need to be very aggressive at instituting special studies as appropriate.
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GUARDING THE BLOOD SUPPLY 49 Surveillance for unknown problems begins with having a high curiosity level and a high index of suspicion and being willing to get back to an appropriate reporting or communication source very early on. It obviously means that it must be incumbent on the public health system that is receiving that report to make an appropriate analysis and pass it up through the system.
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That is where we found all the early cases of HIV infection among both hemophiliacs and transfusion recipients. Because the requests all came to us, we used that file to identify new patients for whom there were no known no risk factors.
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What was useful for us was the presence of a system, a data collection system that existed for another purpose. You must identify such information collection systems that might be useful and that can be justified on an ongoing basis for some other purpose, plug into those systems, and make it somebody's responsibility to look for unusual clinical events.
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We discovered that this wasn't the case when we began to examine mortality data collected from surveys of the hemophilia treatment centers. We found that when these data were compared with the death certificate data, only about two-th~rds of the hemophilia patients were within hemophilia treatment centers.
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It consists of an annual retrospective chart review of all the hemophilia patients within the six states. Most of the patients would be identified in hemophilia treatment centers.
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We currently finance these hemophilia treatment centers for prevention activities. The Health Resources and Services Administration provides these centers with another $5 million a year for health care services.
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De Arman at the University of California, San Francisco, the various hemophilia treatment centers, FDA, and NIH, as well as the various peer groups from the hemophilia population. We hope to obtain 10 to 15 brains per year for this study.
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One of the problems we had during the 1980s was the fact that the hemophilia population didn't want to be identified. There was no registry of hemophilia patients.
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The hemophilia registries are unusual in that hemophilia is a chronic condition, whereas most diseases reported to state health departments are infectious diseases. However, in the states where this surveillance was implemented, the health departments are addressing the issues of chronic diseases.
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and the state health departments. There are other systems, and others are being developed-among them laboratory-based surveillance for antibiotic resistance patterns and hospital-based surveillance.
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An active system, on the other hand, is one where reporting is initiated by a state health decal l~nent. The data are transmitted to CDC from state health departments electronically on a weekly basis and are published in the Morbidity and Mortality Weekly Report.
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There has been talk about active surveillance. The advantages are that you can identify all the cases, you get better-quality data, and some of the data may be useful in special circumstances.
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Increased population density and population encroachment, along with increases in international travel, are the same factors that would likely result in the introduction of some particular pathogen into the blood supply. The top seven emerging infectious diseases in 1993 were cryptosporidiosis, coccidioidomycosis, E
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Then we must studies, and . develop hypotheses, evaluate hypotheses, refine hypotheses and conduct additional lab and environmental implement control measures.
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Bruce Evatt: I am not aware of other groups. I think that hemophilia patients are a unique group in that they are exposed to blood products from large numbers of donors.
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James Allen: If money is to be made available for surveillance for transfusion-transmitted diseases or special issues of that sort, we need to be certain that we have a very strong local, state, and federal disease investigation system and general surveillance process rather than looking to build a superspecialized type of vehicle for something unknown. Instead, our general surveillance system must be very strong.
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