Detailed follow-up of hepatitis B surface antigen positive blood donors.

Brown, Susan (1992). Detailed follow-up of hepatitis B surface antigen positive blood donors. BPhil thesis The Open University.



Although the North West Thames Region collects over 200,000 blood donations each year, less than four cases of post­ transfusion hepatitis B are reported to us annually (Barbara and Briggs 1981) presumably reflecting the exclusion of approximately 40 donors per annum found to be Hepatitis B surface antigen (HBsAg) positive. This study is the first step in the analysis of some of the unique data accumulated on these HBsAg-positive donations over an eighteen year period.

Routine HBsAg screening of all blood donations became mandatory in the U.K. by 1971. Since then, we at the North London Blood Transfusion Centre (NLBTC) have monitored as many HBsAg-positive donors as possible to obtain epidemiological data on HBsAg carriage and the prevalence of other hepatitis B virus (HBV) markers, and to examine ways of predicting the course of HBV infection, so that we can advise carriers concerning their level of infectivity and management of their infection in everyday life. The first section examines the role of HBV in the context of blood transfusion. The serological markers of HBV infection are described in detail, including viral subtypes and a description of mutant and defective strains. The HBV carrier state is then briefly described.

The second section describes current microbiological practices in blood transfusion including the present trend towards laboratory automation.

The third section details the serological assays available for the laboratory detection of HBV infection and an experimental evaluation defines the confidence we can place upon assay results.

Section four is a preliminary analysis of some of the epidemiological data accumulated at the NLBTC over 18 years. 286 HBsAg carriers have been followed up; with particular attention to their HBe antigen and antibody status as the markers most relevant to defining infectivity levels. Of the 35 carriers who were HBeAg-positive at the time of detection, 8 seroconverted from HBe antigen to anti-HBe during the follow-up period. HBeAg positivity was shown to be associated with raised liver function test (LFT) values. Those who seroconverted from HBe antigen to anti-HBe eventually developed normal LFT levels. My preliminary observations on the duration of HBsAg positivity and also on temporal changes in HBsAg titre will form the basis of further work. Although complete in itself, this study also serves as a pilot for a more comprehensive analysis of the wealth of material still to be examined.

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