WHO/BS/2015.2254 Collaborative study for Calibration of Replacement IS for Diphtheria Toxoid for use in Flocculation Test

Overview

We report here the results of a study for the characterization of a preparation of diphtheria toxoid (coded Preparation A) and its calibration in flocculation (Lf) units. Calibration was performed using Ramon flocculation method, standardised using the 2nd International Standard (IS) for Diphtheria Toxoid for use in Flocculation Test (02/176, 1100 Lf/ampoule). Preparation A was found to have a unitage of 1874 Lf/ampoule based on results from 25 laboratories in 15 different countries. A second diphtheria toxoid preparation, coded Preparation B, was included in the same collaborative study and was found to have a unitage of 714 Lf/ampoule. There was good agreement in the results obtained (intra-laboratory and inter-laboratory) for both preparations.