A new mathematical model for fitting an HPL radioimmunoassay curve

A number of mathematical models have been tested for their suitability in representing the dose response curve of a specific assay of the hormone human placental lactogen (HPL).(1)A new equation Y = B[0.14 + 1/[1 + C log [1 + exp[X - D]]] where Y is the percentage activity or counts bound to the antibody and X is the HPL concentration is proposed as representing the overall shape of the curve. This model is shown to give both an accurate representation of the curve and to allow reproducible determination of an unknown over a number of occasions. A number of other models are compared. The new model allows automatic calculation of HPL concentrations from a standard curve using a computer.