A collaborative study to establish a Korea national biological standard for antithrombin concentrate

Background and objectivesSix laboratories consisting of three manufacturers and three national control laboratories participated in a collaborative study to evaluate the suitability of a candidate material to serve as the first Korean National Standard for Antithrombin (AT) concentrate.Materials and methodsThe potency of this candidate preparation was determined using the heparin cofactor chromogenic method. The method is described in the Minimum Requirements for Biological Products in Korea and in the European Pharmacopoeia. The candidate was calibrated against the second International Standard for AT concentrate, coded as 96/520.ResultsThe participants contributed data from a total of 90 independent assays and the results were accepted as statistically valid when the outcome of the analysis exhibited linear dose–response relationships and intersected at a common point at zero dose in the slope–ratio model. The combined potency estimates were obtained by taking the geometric means of results from all assays at each laboratory, and overall potency estimates were calculated as unweighted geometric means of results from all laboratories. The results were expressed in the form of histograms with 95% confidence intervals.ConclusionsAccording to the results of the collaborative study, the candidate preparation showed excellent intra- and inter-laboratory correlations and is judged to be suitable to serve as the Korean National Standard for AT concentrate with the following potency: 51.9 IU/vial (95% confidence intervals = 48.24∼55.98 IU/vial).