TESTING PLASMA POOLS FOR MARKERS OF VIRAL CONTAMINATION - THE UK EXPERIENCE

The transmission of viral infections through the use of products deriv ed from blood has emphasised the need for adequate validation of the p roduction process, testing of materials used in production and quality control tests on the final product. Since the late 1980s, as part of its batch release procedures, NIBSC has tested for markers of viral in fectivity plasma pools used in production of blood products used in th e UK. As a result of testing over 9,000 pools, NIBSC has identified 9 pools contaminated with HBsAg and 2 pools containing antibodies to HIV -1. Since routine screening of plasma pools for anti-HCV was introduce d in 1993, 8 pools out of the 4,000 tested have been found to contain antibodies to HCV. In addition, the release of 12 batches of blood pro ducts was withheld and it is known that further batches of material pr oduced from the positive pools were not submitted for batch release. S tudies involving assays of dilutions of known positive plasma samples indicated that there is considerable variation in the endpoint dilutio ns of antigen or antibody detected by test kits from different manufac turers. The selection and validation of the kits used in such testing is therefore important. The usefulness of standardised low-level exter nal controls in assays of plasma pools for markers of viral infection is discussed.