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Adverse Outcomes in Blood and Blood Component Therapy - page 10 / 19





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procedure may still leave residual concentrations of bacteria on the skin surface33

Thus bacterial contamination of blood and blood component may occur as a result of inadequate aseptic technique during collection or due to transient asymptomatic donor bacteremia. Refrigeration of RBCs usually limits bacterial growth except for cryophilic organisms such as Yersinia sp, which may produce dangerous levels of endotoxin. Yersinia enterocolitica is an increasing problem because the organisms probably originate from bacteremia in the donor and can subsequently multiply at low temperature.36 All RBC units should be inspected daily and before issue for bacterial growth as evidenced by a color change. Because platelet concentrates are stored at room temperature, they have an increased potential for bacterial growth and endotoxin production if contaminated. To minimize growth, storage of PCs are limited to 5 days. It is known that 1 in 1000 to 1 in 2000 platelet units are bacterially contaminated. It is estimated that severe morbidity or death due to bacterially contaminated platelets occurs in as many as 100 to 150 patients every year in the United States alone. It has been suggested that bacteremia is the most common transfusion-related infection today and that the risk of receiving bacterially contaminated platelets may be 50 to 250 times higher than the combined risk per unit of transfusion-related infection with HIV-1/2, HCV, HBV, and HTLV-I/II.37

In the early 1980s, platelet storage for 7 days was approved in the United States. This 7-day storage was based on acceptable in vitro function, in vivo recovery, and survival data. However because of the increasing risk of the proliferation of bacteria the outdate time was reduced to the current 5 days. Recently, reports from Europe have advocated the use of bacteria culturing of platelets on Days 2 or 3 to extend the shelf life of platelets to 7 days, thereby reducing the outdating of platelets and preserving a limited medical resource. Such a strategy is considered cost-effective.37 The US blood supply is considered to be safer now than at any time in recent past however, severe, often fatal, transfusion reactions due to bacterial contamination of blood components continue to occur. Serratia liquefaciens, an uncommon human pathogen, is another recently identified potential cause of transfusion-related sepsis and endotoxic shock. Sporadic case reports implicating this organism in RBC contamination are beginning to emerge. In the United States, five episodes of transfusion-related sepsis due to S. liquefaciens were reported to the Centers for Disease Control and Prevention (CDC) from July 1992 through January 1999.38 Most commonly, contaminating organisms are gram positive skin saprophytes such as Staphylococcus sp. or Bacillus sp.38 Rarely, syphilis is transmitted in fresh blood however storing the blood for over 96 hours at 4 to 6° C kills the spirochete. Although federal regulations require a serologic test for syphilis (STS) on donor blood, infective donors are often seronegative because the test does not detect the spirochetemic state but recipients of infected units may develop the characteristic secondary rash.26

Viral Contamination Hepatitis may occur after transfusion of any blood product. Current infectious disease testing, viral inactivation, and the use of recombinant factor concentrates have significantly reduced the risk. Serum albumin and plasma protein fractions that have been solvent/detergent and heat-treated during manufacture are, with rare exceptions, noninfectious. Laboratory tests for hepatitis that is required for all donor blood include hepatitis B surface antigen (HbsAg), hepatitis B core antibody (anti-HBc), hepatitis C antibody (anti-HCV) and ALT may be used as a surrogate test that might be associated with some form of transmissible hepatitis. The estimated risks of false-negative results on testing of donor blood are hepatitis B (HBV) 1:63,000 and hepatitis C (HCV) 1:103,000. Because its transient viremic phase and concomitant clinical illness likely preclude blood donation, hepatitis A (HAV) is not a significant cause of transfusion-associated hepatitis.26 The implementation of nucleic acid testing (NAT) for the detection of HCV RNA in blood donations is currently a matter of debate. The background to this is the residual risk of posttransfusion HCV infection, which has been calculated by several groups to be approximately 1 per 100,000 to 1 per 200,000 blood donations. This residual risk of virus transmission could mainly be due to test failure or to donations being made during the seronegative window period. This window period was calculated to be an average of 82 days, and HCV RNA testing of blood donations could reduce this markedly.40

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