The International Standard for Endotoxin: evaluation in an international collaborative study

An ampouled preparation of bacterial endotoxin, coded 84/650, was evaluated in 35 laboratories in 12 countries for its suitability to serve as the International Standard for Endotoxin. The ampouled preparation was calibrated in terms of the USA National Standard, EC5, in Limulus Amoebocyte Lysate gelation, turbidimetric and chromogenic tests and in rabbit pyrogen tests. On the basis of the results reported here, with the agreement of the participants in the study, and with the authorization of the Expert Committee on Biological Standardization of the World Health Organization, the preparation coded 84/650 was established in 1986 as the International Standard for Endotoxin for Limulus Gelation Tests with an assigned unitage of 14 000 IU of endotoxin per ampoule.