Report of a collaborative study to assess the suitability of a reference reagent for antibodies to hepatitis E virus.

Several commercial and "in-house" assays have been developed for the detection of antibodies to hepatitis E virus, a major causative agent of enterically transmitted non-A non-B hepatitis. As these kits contain a variety of synthetic peptides or recombinant proteins, greater standardisation is required. A collaborative study was therefore carried out to assess the suitability of a freeze dried preparation designated 95/584 to serve as a reference reagent for hepatitis E virus serum IgG. Preparation 95/584, which is a serum from a previously infected individual, was assayed along with four coded samples, one of which D, was a coded duplicate of 95/584, and three individual sera, coded A, B and C. These preparations were sent to seven laboratories in five countries who tested them in eight different enzyme immunoassays. In most laboratories the coded duplicate gave a mean potency of within 20% of the candidate reference reagent despite the wide range of assays used. However, the potencies of the coded samples which were from different individuals gave somewhat variable potencies relative to the candidate reference reagent. This is not surprising as each sample will have varying proportions of antibodies against individual viral proteins and result in the variation in results observed. Nevertheless, this material will be of use in the standardisation of diagnostic tests for use in sero-prevalence studies and for assessing immunity. Preparation 95/584 was found to be suitable to serve as a reference reagent for hepatitis E serum IgG and has been established as an interim Reference Reagent for Human anti-hepatitis E serum. Each ampoule contains 50 Units per ampoule.