14 - Nucleic acid testing: general view

Summary

Background

Despite thorough measures to select donors and sensitive EIA testing of blood donations, some transmissions of the most relevant transfusion-transmitted viruses, HCV, HIV and HBV, occurred. Even plasma products manufactured from large plasma pools that were additionally inactivated were not completely virus safe. In 1995, plasma fractionation companies were the first to introduce NAT of their plasma pools for fractionation prior to inactivation procedures (see Chapter 20). Although all donors were screened by antibody and antigen tests a high proportion of production pools consisting of several thousand litres of plasma were contaminated with HCV (Scheiblauer et al., 1996). Contamination by HIV and HBV was less frequent. However, those companies introduced NAT not only for HCV, but also for HIV and HBV, as an in-process quality control and to cover any potential failures in good manufacturing process. The quality requirements for HCV NAT were set at a detection limit of 100 IU/ml for pools of source plasma used for plasma-derived medicinal products. These requirements have been in force since 1 July 1999 (CPMP/BWP/390/1997; European Pharmacopoeia 2001). As soon as it was shown that NAT was feasible as a quality control measure in the plasma industry it fuelled discussions on whether these new techniques could also be applied to routine blood donor testing.

The plasma fractionation companies started to perform diagnostic testing on mini-pools of donor samples containing between 500 and 1000 individual samples, prior to carrying out pooling of several thousand donations for fractionation, to avoid the loss of whole pools of plasma in the event of a positive HCV RNA test.