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Adverse Outcomes in Blood and Blood Component Therapy - page 11 / 19





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Human immunodeficiency virus (HIV) in the USA is almost entirely HIV-1, although HIV-2 is also of concern. Testing for antibodies to both strains is required. HIV-1 p24 antigen testing is also required for all donor blood. Additionally, blood donors are questioned about behaviors that may put them at high risk for HIV infection. The estimated risk of a false-negative result on testing of donor blood is 1:676,000. A few cases have been acquired from donors in an early infectious seronegative phase.26 Herrera et al41, evaluated the usefulness of the STS in preventing the transmission of HIV, HBV and HCV, and human T- lymphotropic virus (HTLV) via the transfusion of seronegative, infectious window-period blood. They analyzed the demographic and laboratory information on blood donations made between January 1992 and June 1994 in 18 American Red Cross regions. They assumed that the same proportion of HIV-positive and HIV-infectious window- period donations reacted on STS and were negative on other screening tests such as HBV, HCV, and HTLV. This proportion multiplied by the estimated number of HIV-infectious window- period donations is the number of post-screening HIV-infectious donations removed by STS. The result showed that out of 4,468,570 donations, 12,145 (0.27%) were STS positive and 377 (0.008%) were HIV positive. Among donations that were negative on other screening tests, STS-reactive donations were 12 times more likely to be HIV positive. However, of an estimated 13 infectious window- period donations, 0.2 would have been removed because of a reactive STS, at a cost of over $16 million. Thus STS is a poor marker and a costly strategy for preventing post-screening HIV infections and other blood-borne diseases.41 Cytomegalovirus (CMV) can be transmitted by leukocytes in transfused blood. Because its effects are absent or mild, routine CMV antibody testing of donor blood is not required. However, CMV may cause serious or fatal disease in immunocompromised patients, who should receive CMV-negative blood products that have been donated by CMV antibody-negative donors or leukocyte depleted by filtration. Fresh frozen plasma (FFP), which contains virtually no intact leukocytes is not considered a risk for CMV transmission.26 Whether transfusion increases the risk of AIDS-defining cytomegalovirus (CMV) infection (CMV AIDS) in immunosuppressed patients is not known. Because of concerns about the risk of transfusion transmission of CMV and potential exposure to multiple strains of CMV through transfusion, the National Hemophilia Foundation recently recommended that CMV-negative blood be used in HIV positive hemophiliacs, regardless of their CMV serologic status. Although the multiple strains of CMV cause different CMV disease manifestations in transplant recipients, there are no data on CMV disease in HIV positive hemophilia.42

Human T-cell lymphotropic virus type I (HTLV-I), causes adult T-cell lymphoma/leukemia, HTLV-I-associated myelopathy, tropical spastic paraparesis, and posttransfusion seroconversion in some recipients. All donor blood is tested for HTLV-I and HTLV-II antibodies. The estimated risk of false-negative results on testing of donor blood is 1:641,000.26 A program to prevent transmission of HTLV-I by blood transfusion through implementation of anti-HTLV-I screening of donated blood by particle agglutination (PA) method was instituted in Japan in 1986. Since then, many developed countries have introduced this technique, even though they have very low HTLV-I carrier rates compared with the rates in Japan. In 1990, a second-generation PA kit was released for donor screening in Japan. This kit has two improvements. The first is a reduction of false-positive reactions, made possible by decreasing the ratio of core proteins (mainly p19) of gelatin particles, which were coated with cell lysates of HTLV-I cell lines as specific antigens. The second is avoidance of false-negative prozone reactions. The reaction disappears when an increased percentage of env antigens are added. The risk of HTLV-I transmission after screening is thought to be very small, although there are no confirmation data.43

Other Viruses About 3 years ago, a group of Japanese researchers discovered a new virus called TT virus (TTV), after the name of the patient in whose blood it was initially identified. The TTV is a small, unenveloped virus with a single-stranded circular DNA genome of negative polarity. Analysis of its genome organization suggests that TTV may be related to the Circoviridae, or it may eventually form a new virus family designated Circinoviridae. The existence of several genotypes of the virus has been demonstrated by studies. It was initially detected in the plasma of Japanese patients with posttransfusion non-A-G hepatitis. Other investigations indicate

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