SCREENING PROCEDURES TO PREVENT TRANSMISSION OF HEPATITIS B, NON-A,NON-B, AND AIDS BY BLOOD TRANSFUSION
Authors: Seidl S 
Published: August 2018

Although the number of infectious agents capable of being transmitted through blood and blood products is vast, only a few cause problems in recipients of a magnitude which warrants the need for screening tests. The most important agents are Hepatitis B Virus (HBV), Hepatitis non-A,non-B (HNANB) - agents causing posttransfusion hepatitis (PTH) and the human immundeficiency viruses (HIV) responsible for transfusion associated AIDS (TAA).

PTH: Prospective studies in open-heart-surgery patients demonstrated a high prevalence (8-17%) *in Spain, Italy, the United States and Israel whereas low percentages (2-5%) were observed in Australia, Finland and West-Germany. Among haemophiliacs acute and chronic hepatitis is a rather frequent complication. Serologic markers of HBV infection have been observed in the majority of patients. Since HBsAg screening has been introduced most cases of PTH (>90%) are due to infection with HNANB-agents. For this type of hepatitis no specific assay exists. It has been suggested that surrogate tests (ALT, anti-HBc screening) might serve as interim screening measure. In prospective studies in the USA a correlation has been observed between donor ALT and recipient hepatitis, but not more than 30% of PTH can be prevented at a loss of 1,5 to 3,0% of the donor population. Similar data have been reported when blood donors were screened for anti-HBc. There was a significantly higher incidence of PTH in recipients receiving at least one unit of anti HBc positive blood. This was recently confirmed in a study in which patients received blood with ALT-levels below 30 IU/ml. The incidence of HNANB was 2,1% after transfusion with anti HBc negative blood whereas 10,1% developed HNANB when anti HB positive blood was transfused (P=< 0.0001). However, these two markers (ALT, anti HBc) do not identify the same NANB carrier population. - ALT screening and testing for anti-HBc have been recently instituted in the USA as “surrogate tests” for detecting HNANB carriers.

TAA: Among the total number of AIDS cases there ist a small percentage caused by transfusion of blood and blood products. In the USA approximately 2% of TAA have been reported, 1 % of AIDS patients are haemophiliacs but the majority of haemophiliacs are HIV-antibody positive. According to a survey of the Council of Europe (March 1986) the percentages of HIV positive European haemophiliacs varies between 4 to 8% (Belgium, Norway) and 30 to 60% in other European countries. The number of TAA-cases is around 1%, AIDS among European haemophiliacs has been observed up to 5% of the total AIDS cases. - Screening for HIV antibodies in blood donors was introduced in most European countries and the USA in early summer 1985, but several thousands of recipients of HIV positive blood (issued before) are now virus carriers. This has been confirmed in “look back” programmes: A substantial number of recipient (50 to 90%) has been found to be HIV positive.-A major disadvantage of the HIV antibody test is the fact that antibodies appear several weeks after infection. The gap between infection and detecting HIV antibodies may be reduced by an antigen test, which recognizes the HIV infection as early as two weeks after infection. - The recent detection of HIV 2 implies the necessity of developing tests for the identification of variants of HIV.