Viral markers screening and transfusion safety

Abstract

Current residual infection risk by transfusion for hepatitis B and C viruses (HBV, HCV) and for human immunodeficiency virus (HIV) is the lowest in the history. It has been achieved mainly by introduction of serological markers screening (HBsAg, anti-HCV and anti-HIV) and nucleic acid testing (NAT). These procedures allow identifying donors infected in chronic and very early stages of the infection.

The incidence and prevalence of HBV and HCV infection among blood donors in Poland remain stable, however in the case of HIV, in recent years, an increasing trend is seen.

The residual risk of infection is associated primarily with diagnostic window. For donations tested individually, this period is estimated to be 11.6, 1.5, 3.3 days for HBV, HCV and HIV, respectively. In the case of screening in plasma pools of eight donations it is calculated for 18.2, 2.7 and 5.5 days. Particularly for HIV, polymorphism at the genomic level is an additional risk factor.

Recent observations confirm that, infectivity during window period is very high – even single virions could transmit infection. At the final stage of chronic HBV infection (OBI) infectivity is still significant but much lower (about 1,000 copies).

In recent years it has been demonstrated that increased analytical sensitivity translates into a significant improvement of the clinical sensitivity. Further reduction of the diagnostic window for individual donations testing is possible by increasing the efficiency of the extraction and amplification (e.g. HBV in Ultrio Plus and Ultrio Elite) or by increasing the volume of the test sample (e.g., HCV and HIV in tests based on TMA or PCR). It was demonstrated that the amplification of more than one region of the HIV genome contribute to the recovery/improvement of clinical sensitivity lost in the case of blood donations infected with escape mutants.

One way to reduce the number of infected donors is to improve selection process involving questionnaire and interview before every donation. The process should be updated based on the analysis of current sources of infection.