Page 286 - AIDSBK23C

Page 286

BLOOD AND TISSUE BANKING AND AIDS

The AIDS epidemic has markedly modified screening procedures in blood and tissue
banks. Transfusion-associated AIDS early in the epidemic accounted for some cases of AIDS,
particularly in persons with hemophilia. Current and future retroviral laboratory screening tests
for HIV, first initiated in 1985 in the U.S., have eliminated virtually all of the risk. In the U.S.
blood products are currently screened for antibodies to HIV1/2, HTLVI/II, hepatitis B, hepatitis
C (HCV) and syphilis. Testing is also performed for donor ALT (SGOT) levels, for the presence
of hepatitis B surface antigen, human immunodeficiency virus (HIV) p24 antigen and, using
nucleic acid amplification testing (NAT), for HIV and HCV nucleic acids. Despite excellent
methodology, however, the tests employed are not perfect, and blood-containing HIV may very
rarely be released for transfusion. Since patients receiving transfusions may die from their
primary disease or other causes prior to onset of AIDS, then the overall risk for transmission
HIV infection from transfusion is extremely small---on average only 1 case in 1 900 000 single
donor units of screened blood in the U.S.[162] For the years 2006 to 2009 the incidence was
estimated to be 1 in 8 000 000 donations in a Canadian study.[163] This risk remains low with
repeat blood donors.[1120] Behavioral risk factor screening appears to be effective in reducing
the risk for HIV infection through blood products.[1121]
In populations with a low prevalence of HIV, including most developed nations, the risk
for HIV transmission by blood products is very low, while in some larger metropolitan areas or
in parts of Africa or Asia, the risk is higher. In developing nations where blood screening is not
rigorous, 5 to 10% of HIV infections may be acquired through use of blood products. Despite
economic hardships in many regions, the screening of blood donors for HIV is a cost-effective
strategy to prevent the spread of HIV, particularly in areas where seroprevalence of HIV is >5%.
Additional strategies to reduce the spread of transfusion-associated HIV infection include:
elimination of paid donors, reduction in use of family members to donate blood for a patient,
institution of guidelines for judicious use of transfusion therapy, and prevention of severe
st
anemias.[164] During the first decade of the 21 century, 80.7 million blood units were collected
globally in 167 countries during 2004-2005, of which 77.3 million were tested for HIV and at
least 0.6 million of the remaining 3.4 million donations went untested. Of 192 United Nations
member countries, 125 reported 100% compliance with HIV testing of donated blood.[1122]
Current screening tests include EIA for both HIV-1 and HIV-2 (though the prevalence of
the latter outside of West Africa is very low) and HIV-1 p24 antigen.[1123] Addition of testing
for HIV-1 p24 antigen, which can detect some newly HIV-infected persons in the EIA
seronegative “window,” is estimated to find approximately one infected blood donor per 6
million donations in the U.S.[164] As EIA screening test performance improves, the
seronegative window period becomes more important. Nucleic acid amplification tests (NAT)
for HIV RNA have reduced the window period more than p24 testing, reducing the risk of HIV
transmission from blood products to less than 1 in 1 900 000, but show poor cost-
effectiveness.[1124] The cost effectiveness of NAT-based screening is estimated to be $4.7 to
11.8 million U.S. dollars per quality-adjusted life-year.[1125] In populations where the
incidence of new HIV infections is increasing, this potential window error becomes more
important.[1126] Testing by donor centers in the U.S. since 1989 is also routinely performed for
HTLV I and HTLV II.[109]