Development and validation of a monoclonal antibody enzyme immunoassay for measuring progesterone in saliva

A nonextraction, competitive, solid-phase enzyme immunoassay with a monoclonal antibody was developed and validated for measuring progesterone in saliva. The antibody was raised against 11 alpha-hydroxyprogesterone hemisuccinate-bovine serum albumin conjugate and was indirectly immobilized to the walls of microtiter wells. The labeled analyte (progesterone-horseradish peroxidase conjugate) was homologous with the immunogen. The lower detection limit (concentration equivalent to B0-3 SD) was 38 pmol/L of saliva sample. We validated the assay with studies to establish the independence of the concentration determined from the volume of saliva assayed, quantitative recovery of progesterone added to saliva, interference from possible cross-reactants, and agreement with a similar assay that incorporated an extraction step. In addition, we determined luteal-phase concentrations of salivary progesterone in normal women and compared the results with those of an older assay involving a polyclonal antibody.