Summary
Eighteen laboratories participated in a collaborative study to calibrate a replacement
for the 1st International Standard for Antithrombin, Concentrate (88/548). Excellent
agreement between laboratories, as indicated by mean % gcv of 3.3 and 5.9 for functional
and antigenic assays, was observed when the candidate concentrate (96/520) was assayed
against the 1st International Standard for Antithrombin, Concentrate (88/548). The
functional potency was found to be 7.9% (p <0.05) lower than the antigenic potency.
Based on the results and with the agreement of the participants of this study and
the authorisation of the Expert Committee on Biological Standardisation of the World
Health Organisation, the antithrombin concentrate, coded 96/520, has been established
as the 2nd International Standard for Antithrombin, Concentrate, with labelled potencies
for both functional (4.7 IU/ampoule) and antigenic (5.1 IU/ampoule) activities.
