INTERNATIONAL COLLABORATIVE STUDY BY IN-VITRO BIOASSAYS AND IMMUNOASSAYS OF THE FIRST INTERNATIONAL STANDARD FOR INHIBIN, HUMAN RECOMBINANT

The First International Standard for Inhibin, Human Recombinant, (ISI) , a lyophilized preparation of rDNA-derived human 32 kDa Inhibin A in ampoules coded 91/624, was evaluated by international collaborative st udy for its suitability to serve as an International Standard. This st udy, which involved 15 laboratories in nine countries, included a vari ety of in vitro bioassays and immunoassays. The ISI was compared with two other lyophilized preparations of human recombinant inhibin, the I nternational Standard for Porcine Inhibin (ISP) and preparations of hu man follicular fluid inhibin. Predicted loss of activity based on esti mates of potency of contents of ampoules which had been stored under c onditions of accelerated thermal degradation indicated that the ISI ha s satisfactory stability. On the basis of the results of this study, t he ISI was deemed suitable to serve as a standard for in vitro bioassa ys and immunoassays and was established by the Expert Committee on Bio logical Standardization of the World Health Organization as the First International Standard for Inhibin, recombinant human, with an assigne d unitage of 150 000 International Units per ampoule. This unitage mai ntains an approximate continuity of units with the ISP. (C) 1996 The I nternational Association of Biological Standardization