Isoluminol as a marker in direct chemiluminescence immunoassays for steroid hormones

We have used isoluminol steroid hormone conjugates in competitive heterogeneous chemiluminescence immunoassays (CIA) for estradiol, progesterone and estriol in body fluids. The assays did not require prior extraction of the steroid hormone with an organic solvent. Polyclonal or monoclonal antibodies, covalently coupled to polyacrylamide microspheres or adsorbed onto the plastic surface of microtritation plates via an intermediate second antibody, were used as solid-phase. The latter solid-phase system allows rapid processing of incubation mixtures. Sensitive and reliable direct CIAs for estradiol in serum, progesterone in serum and in saliva and for estriol in saliva have been developed and their clinical utility has been assessed. Sensitivities ranged from 0.54 to 0.04 nmol/l, and precision (% CV) ranged from 10% to 16%.