A three-parameter langmuir-type model for fitting standard curves of sandwich enzyme immunoassays with special attention to the α-fetoprotein assay

In a simplified approach to the reaction kinetics of enzyme-linked immunoassays, a Langmuir-type equation y = [ ax (b + x) ] + c was derived. This model proved to be superior to logit-log and semilog models in the curve-fitting of standard curves. An assay for α-fetoprotein developed in our laboratory with a sensitivity of 2 g/liter and a between-day coefficient of variation of about 15% was used for comparison of the different models. The proposed model has the advantage that it is based on the law of mass action and that blank determinations can be included in the calculation of the curves without giving a disproportionate bias.