An International Collaborative Study of the assay of human placental lactogen: Establishment of WHO International Reference Preparation of human placental lactogen.

A reference preparation of human placental lactogen (HPL) for use in immunoassays is described. In an international collaborative study is was found to be stable and suitable for use as a standard for HPL in plasma. Estimates of HPL in plasma made in different laboratories agreed more closely when expressed in terms of this reference preparation than in terms of individual laboratory standards. The reference preparation is available in ampoules (coded 73/545) which each contain an identical amount of HPL, found in the study to be approximately 850 microgram. The preparation has been established as the International Reference Preparation for HPL for immunoassay and, based on the results of the study, the content of each ampoule is defined as 850 micro International Units.