Monday, 22 December 2008

BLOOD TRANSFUSION - 1

Blood transfusion is not always safe for the recipients. In most of the countries , standard tests those are conducted to detect any infection in donor's blood are not full proof. I wrote an article on this for someone but the article remained with me for some reason. I would like to share the information it has with you. Since the article is long enough , I am going to publish it in few installments.

INTRODUCTION

Hepatitis B is the dreaded disease, especially when it is transmitted through blood received from donation. The detection of hepatitis B in blood became easy when hepatitis B surface antigen (HBsAg) was discovered. This helped decrease the occurrence of hepatitis in post-transfusion scenario. As such this has been a major breakthrough to arrest the spread of hepatitis B through blood transfusion. This helped the detection of hepatitis B ‘e’ antigen, hepatitis B core antigen (anit-HBc) and HBsAg as well. The common method of detecting hepatitis B infection is screening the blood by enzyme linked immunosorbent assay or ELISA for HBsAg. But this could not rule out the incidence of post transfusion incidence of hepatitis B with the receiver of blood from donor totally. This is because during a phase called “window period”, the screening of blood for detecting of the viral presence does not work fully. During this period the virus of hepatitis B can escape the detection for the serological response of host to infection, so HBsAg can avoid detection their presence in blood though the infection of hepatitis B virus is present. This “window phase” denotes a period when the disease is carried but not effective, so this poses a definite hazard to the recipient of blood from the donor who is going through “window phase”. It necessitates during the `the window period` marking the antibody of hepatitis B core antigen (anti-HBc) which could serve as a serological marker of hepatitis B infection.
The conventional blood tests fail to serve this purpose. That is why blood transfused from apparent healthy donors with anti –HBc of IgG variety; that may not affect the donors due to presence of high anti bodies of HBsAg (anti HBs) since they are protective in nature. But it may infect the healthy recipient with the virus of hepatitis B in case of blood transfusion from such donors. In many ethnic groups or countries; there are high incidences of presence HBsAg, so it is obvious that there is lots of scope for inadvertently transfusing HBV infected blood. Therefore the need arose for a marker that should be used for blood screening on such population while they are on such “window period or phase”. A marker what helps to detect the presence of hepatitis B virus during this period (Hoofnagle, Seef, Bales, et al.1978 : Douglas, Taswell, Rakela, Rabe.1993) by screening the donors blood for anti –HbcAg antibody amongst the IgM type and at the same time detecting the antibodies to hepatitis B core antigen IgM type i.e anti-HBcAg in the donor population.


To be continued................

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