In a simplified approach to the reaction kinetics of enzyme-linked immunoassays, a Langmuir-type equation y = [ux/(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 a-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. o 1987 Academic Press, Inc.

Three different methods for the measurement of glycated haemoglobin or HbA1, based on agar gel electrophoresis, ion-exchange and affinity chromatography were compared. All three showed acceptable precision (overall CV being less than 5%) and correlated well with each other (r greater than 0.945). The ion-exchange and affinity chromatography method proved to be independent of the amount of pre-HbA1c present. The electrophoresis method was independent of temperature in contrast to the other two methods, which showed a strong and comparable temperature dependency. All three methods were dependent on the haemoglobin concentration and/or protein content of the haemolysate. Both ion-exchange and electrophoresis showed significant interference by changes in haemoglobin concentrations, whereas the protein concentration significantly biased the affinity chromatography figures. Taking into account their specific merits all three methods are acceptable for routine use.

No abstract