STANDARDIZATION OF GENOMIC AMPLIFICATION TECHNIQUES FOR THE DETECTIONOF VIRAL CONTAMINATION OF BLOOD AND BLOOD PRODUCTS

Occasional transmissions of viral diseases still occur despite the scr eening of donors for viral markers (anti-HCV and anti-HIV antibodies a nd hepatitis B surface antigen) as a result of inclusion of 'window-pe riod' donations and/or breakdown in good manufacturing practice. Intro duction of genomic amplification techniques (GAT) for the detection of viral nucleic acids in plasma pools should further increase the safet y of plasma-derived products. For some viral contaminants such as HAV and human parvovirus B19 GAT assays are the only methods available for screening plasma pools and blood products for the presence of virus. The present interlaboratory variation in sensitivity of GAT assays cou ld be reduced by the use of working reagents or standards. At NIBSC, w orking reagents for HCV, HIV, HAV and B19 have been established based on the results of collaborative studies. Analysis of the performance o f the NIBSC HCV working reagent over a period of 2 years has indicated an increase in sensitivity and consistency of assays. Preliminary dat a on the NIBSC HIV working reagent has indicated differences in the se nsitivity of different commercial assays. A collaborative study to ass ess the suitability of materials for an international standard for HCV has been completed. A lyophilised preparation, genotype 1, has been c hosen as the candidate international standard and assigned a concentra tion of 10(5) international units/ml, The international standard, when established, will provide a common unit of measurement against which all working reagents and standards would be calibrated. The establishm ent of working reagents and international standards should minimise in terlaboratory variation in sensitivity of GAT assays and should provid e a basis for comparison of data from individual laboratories.