PATHFAST, a novel chemiluminescent enzyme immunoassay for measuring estradiol in equine whole blood and serum

A novel chemiluminescent enzyme immunoassay system, PATHFAST, for the measurement of estradiol in horses was evaluated. The concentrations of estradiol in the whole blood and serum of mares were measured using PATHFAST and the estradiol concentrations measured by PATHFAST were compared with those measured by a time-resolved fluoro-immunoassay (FIA). To monitor physiological changes, serum estradiol concentrations in mares were measured using PATHFAST throughout the gestation period. The serum estradiol concentrations correlated highly with those in whole blood samples. The serum concentrations of estradiol measured by PATHFAST also correlated well with FIA. Circulating estradiol increased during mid-gestation and high levels of serum estradiol were maintained in late gestation, followed by an abrupt decline to term. These results demonstrate the utility of PATHFAST in equine clinics as an accurate diagnostic tool for the rapid assay of estradiol within 26 min using unextracted whole blood.