The international standard for atrial natriuretic factor. Calibration by an international collaborative study.

An ampouled preparation of human atrial natriuretic factor, ANF-(99-126), was evaluated by 23 laboratories in 10 countries for its suitability to serve as the international standard for ANF. The preparation was calibrated by radioimmunoassay, radioreceptor binding assay, and bioassay and was shown to have satisfactory stability and biological activity. Estimates of the ANF content of a set of specimens of plasma in terms of the standard showed agreement in ranking order when the ANF was extracted prior to assay. However, estimates of the ANF content of the plasmas in terms of either the international standard or the various local standards varied widely among laboratories. 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 85/669 was established in 1987 as the international standard for ANF, with a defined potency of 2.5 international units per ampoule.