A global standard for anti-D immunoglobulin: international collaborative study to evaluate a candidate preparation

The aim of the study was to evaluate a lyophilized anti-D immunoglobulin preparation to serve as a global standard for potency assays of anti-D immunoglobulin products.

The candidate global standard, 01/572, was calibrated against the World Health Organization (WHO) International Reference Preparation (IRP) for anti-D immunoglobulin, human (68/419), along with two reserve candidate reference preparations, in an international collaborative study involving 25 laboratories in 15 countries. The United States Food and Drug Administration (US-FDA) Center for Biologics Evaluation and Research (CBER) Standard for anti-D immunoglobulin, Lot 3, was included for comparison. Most laboratories (20/25) performed AutoAnalyser methodology, competitive enzyme-linked immunoassay (EIA) and/or flow cytometry.

The overall mean potency of the candidate global standard, 01/572, was 284.5 international units (IU)/ampoule, with an interlaboratory variability, expressed as a percentage geometric coefficient of variation (% gcv), of 9.7. The mean potency of the US Standard was 859.4 IU/ml with an interlaboratory variability of 9.5% gcv, excluding an outlier. The mean potencies of the reserve preparations per ampoule/vial were 110.6 IU and 106.7 IU when calibrated against the IRP, and 112.2 IU and 106.6 IU when calibrated against 01/572, respectively, with interlaboratory % gcv values of 9.6-18.3 (excluding outliers).

Preparation 01/572 proved more suitable for use as a global standard than the reserve candidate preparations and was established, with an assigned potency of 285 IU/ampoule, by the WHO as the 2nd International Standard for anti-D immunoglobulin; by FDA-CBER as the Standard for anti-D immunoglobulin, Lot 4; and by the European Directorate for the Quality of Medicines (EDQM) as the 1st Biological Reference Preparation for anti-D immunoglobulin.