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

Abstract

Background and objectives: 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).

Materials and methods: 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.

Results: 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%.

Conclusion: 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.