One-point recalibration of heterogeneous enzyme immunoassays with non-linear calibration curves

We have investigated one-point recalibration of heterogeneous enzyme immunoassays involving nonlinear calibration curves. By using a factor determined from a single standard we updated calibration curves obtained earlier by means of multiple-point determination. The prerequisite for this method is a reproducible working procedure, i.e., as ensured by a fully mechanized system. In our investigations with Enzymun-Test system ES 600 (Boehringer Mannheim) we determined alpha 1-fetoprotein, carcinoembryonic antigen, digoxin, ferritin, thyroxin-binding globulin, triiodothyronine, and thyroxin in human serum pools over a period of two weeks with both full calibration and one-point recalibration. Comparisons of the results thereby obtained show that the means of the concentrations and the CVs for the alternative calibration procedures differed negligibly, even if we used reagents exposed to different temperatures for different periods of time. With the one-point recalibration procedure presented here, therefore, one can considerably reduce the time and effort spent on calibration.