Direct solid-phase enzyme immunoassay of progesterone in saliva

We have developed a rapid enzyme immunoassay for progesterone in saliva. This solid-phase assay is carried out on microtitre plates with no extraction or centrifugation steps. The detection limit of the assay is 200 fg per well (3.2 pmol/L). Intra- and interassay coefficients of variation for low, medium, and high concentrations of progesterone were 7.5, 16.0; 9.1, 8.3; and 8.7, 6.7%, respectively. Correlation between total plasma progesterone (assayed by enzyme immunoassay with extraction) and salivary progesterone concentrations was good (r = 0.848, p less than 0.001, n = 56). We found the assay useful for monitoring ovarian function. The analytical procedure is convenient, and one person can assay more than 200 saliva samples per working day. The turnaround time for 36 samples is 2 h, including 1.5 h of incubation time, when previously coated plates are used. We conclude that such assays are very suitable for measuring progesterone in serial saliva samples and could become the preferred method for monitoring ovarian function.