Calibration of the second International Standard for hepatitis B immunoglobulin in an international collaborative study

Abstract

The International Standard for hepatitis B immunoglobulin is used in the standardization of the anti-HBs content of immunoglobulins for prophylactic and therapeutic use and also in the standardization and calibration of quantitative diagnostic anti-HBs assay kits. A collaborative study was undertaken to assess the suitability of a candidate Second International Standard (2nd IS), and to calibrate it in International Units (IU). The candidate 2nd IS was prepared from a bulk of 5% hepatitis B immunoglobulin (NIBSC code 07/164). Twenty-two participants from 12 countries assayed the first IS, the candidate 2nd IS, a freeze-dried pool of plasma containing anti-HBs and a plasma from a blood donor. These samples were assayed with 19 different assay kits. Data from 102 assays were received. The mean potencies of two coded samples of the candidate 2nd IS were 100.7 and 101.4 IU/ml (combined potency 101.0 IU/ml). The geometric coefficients of variation for these samples were both 13%. The predicted long-term stability of 07/164 was assessed by assaying samples stored at elevated temperatures for a period of 6 months. 07/164 was predicted to be stable at -20 degrees C with the estimated % loss per year of below 0.2%. 07/164 was established as the 2nd IS for hepatitis B immunoglobulin with an assigned potency of 100 IU/ampoule by the WHO Expert Committee on Biological Standardisation. The United States Food and Drug Administration has adopted the same standard as the new Reference for Hepatitis B Immunoglobulin, Lot 3.