A collaborative study to establish the second national standard for antithrombin concentrate in Korea

This study aimed to establish a second national standard for antithrombin (AT) concentrate that can be used for potency assays of AT products. A collaborative study was conducted involving four laboratories, including national control laboratories and manufacturers in Korea, and the suitability of a candidate material to serve as the second national standard for AT concentrate was evaluated. The candidate material was manufactured using a process approved for Good Manufacturing Practices. The potency of the candidate was determined using the heparin cofactor chromogenic method. The candidate was calibrated against the third International Standard for AT concentrate (code 06/166). Participants provided data from 58 independent assays. Combined potency estimates were calculated by determining the geometric means of the results obtained from all assays performed at individual laboratories. The overall potency assessments were subsequently established as the geometric means of all results collected from all laboratories. According to the collaborative study results, the intra- and inter-laboratory variability showed acceptable geometric coefficient of variation of 1.2 %-3.4 % and 2.4 % respectively, and it deemed to serve as the Korean national standard for AT concentrate with the assigned potency as follows: 32.1 IU/vial (95 % confidence interval; 31.7-32.5 IU/vial).