Standardisation of nucleic acid amplification techniques (NAT) for the detection of viral contamination of blood and blood products

The standardisation of NAT assays (both sensitivity ands specificity) can b e achieved by the use of commonly accepted standards in all assay runs. Bas ed on the results of collaborative studies organised by NIBSC, working reag ents for NAT assays for HCV RNA, HAV RNA, HIV RNA and parvovirus B19 DNA ha ve been established. Data on the performance of the HCV working reagent ove r approximately two years have indicated an improvement in the sensitivity of assays, both in-house and commercial. A WHO International standard for H CV RNA NAT assays was established in 1997 based on the results of a collabo rative study. This standard is a lyophilised preparation of a genotype 1 is olate diluted in HCV-negative cryosupernatant. The HCV RNA content is expre ssed in International Units (IU) and each vial of the standard contains 50 000 IU. Preliminary work has indicated that 1 IU is approximately equivalen t to 5 genome equivalents.