Chemluminescence immunoassay for estriol in saliva

Estriol is determined in whole saliva of pregnant women by a direct solid-phase chemiluminescence immunoassay. The assay uses a monclonal antibody raised against estriol-6-crboxymethyloxime/bovine serum albumin and the homologous chemiluminescent marker conjugate estriol- 6-carboxymethyloxime/aminopentylethylsiolominol (E3/APEI). The anti-estriol antibody is bound to the wells of a microtitration plate via a second antibody directed against the monoclonal antibody; 50 μl of saliva and 12.5 pg of E3/APEI per well are used. The incubation time is 10 min at room temperature. The calibration graph covers 5–750 pg of estriol and the detection limit is 4.5 pg (0.31 nmol l^-1. Mean recovery of added estriol is 98%. Within-assay coefficient of variation is 11.8–5% for 0.21–6.5 nmol l^-1 E3, and the between-assay value is 15.7–6.9% for 0.27-3.5 nmol l^-1 E3. The correlation of E3 concentration in time-matched samples of saliva and sera from pregnant women was good (r = 0.934). Total assay time including calculation of results is 3 h for 40 saliva samples.