THE MEASUREMENT OF ESTRONE-3 GLUCURONIDE IN URINE BY NONCOMPETITIVE IDIOMETRIC ASSAY

We report a novel non-competitive idiometric assay for the measurement of oestrone-3-glucuronide (EG) in diluted urine. The method is based on the use of two types of anti-idiotypic antibody, the beta-type and alpha-type, that recognize different epitopes within the hypervariable region of the primary anti-EG antibody (Ab(1)). The beta-type anti-id iotypic antibody is analyte sensitive and competes with the analyte fo r an epitope of the primary antibody at the binding site. On the other hand, the alpha-type is analyte insensitive, but does not bind the Ab (1) in the presence of the beta-type due to epitope proximity. In the present format, reaction mixtures containing the europium labelled Ab( 1) are reacted sequentially with EG standards or diluted urine samples , with the beta-type anti-idiotypic antibody and biotinylated or-type anti-idiotypic antibody on immobilized streptavidin coated microtiter plates. After 1 h incubation, the fluorescence of europium is measured by a time-resolved fluorescence and is proportional to the concentrat ion of EG over a range of 0-10 nmol/l. The method demonstrates good se nsitivity, precision and comparability with an alternative competitive fluorescent immunoassay. The idiometric assay for EG may be applied f or the monitoring of ovarian function in women and is suitable for dip stick technology.