6-ALPHA-BIOTINYLATED ESTRONE - NOVEL TRACER IN COMPETITIVE CHEMILUMINESCENCE IMMUNOASSAY OF ESTRONE IN SERUM

We describe the development and validation of a labeled-hapten competi tive immunoassay for determining total estrone in serum. For the hapte n tracer we use the Ga-biotinylated estrone derivative, 3-hydroxyestra -1,3,5(10)-trien-17 -one 6 alpha-N-(epsilon-biotinyl)aminocaproamide ( Bio-E1). A specific polyclonal rabbit anti-estrone antibody is indirec tly bound via an immobilized donkey anti-rabbit antibody on microtiter plate wells. The amount of Bio-E1 bound is then measured with strepta vidin-horseradish peroxidase conjugate, whereby the enzyme activity is quantified by an enhanced chemiluminometric method. For the assay, se rum samples were extracted with solid-phase extraction cartridges. The assay dynamic range was 93-7400 pmol/L estrone, with a lower detectio n limit of 55 pmol/L. An interassay imprecision (CV) of 12-14%, a reco very rate between 80% and 110%, and a dilution linearity are demonstra ted. Estrone serum concentrations were measured in healthy men and wom en and in women with polycystic ovary syndrome. Comparing the assay wi th a nonextraction RIA, we found an acceptable correlation for samples from 143 subjects of either sex. This enzyme immunoassay with biotin as the primary label and enhanced chemiluminescence signaling detectio n performs well for determining total estrone in serum and is readily adaptable to assays for other steroid hormones.