The biometry of an isotope displacement immunologic microassay

Bioassay micro techniques have been used widely in determining the potency of insulin as well as for estimating the strength of many other biological substances. The development of micro bioassay methods which rely on the antigenic specificity of the biological substance being assayed is an encouraging recent development. Such immunoassay procedures, which are both reliable and practical, appear to provide a general method for the measurement of many biological substances. The present study is concerned with certain biometric aspects of isotope displacement immunoassays. General principles associated with such assays are presented, and the primary sources of variation are discussed. A nonlinear statistical model, based upon the assumption of univalent antigen and a single order of antibody combining sites, is developed. Procedures are outlined and numerically illustrated for inverse point and interval estimation for this model. Specific examples illustrating the procedure are drawn from the diabetes and insulin literature. This is done because the procedure was first developed for assaying minute quantities of insulin and is most widely used for this purpose. However, it should be noted that the method has been successful in many other applications as well.