Radioimmunoassay of progesterone in saliva: application to the assessment of ovarian function.
Level 4 - case-series / case-control
Small observational diagnostic validation study and case series
What was done
Researchers developed and validated a specific radioimmunoassay (RIA) requiring 400 µL of mixed saliva to measure progesterone concentrations. Saliva was collected daily for at least 28 days from 13 normal women (4 provided matched plasma samples for cycle dating with plasma progesterone, estradiol, lutropin, and follitropin; 9 provided saliva only to construct a provisional normal range) and 3 patients from an infertility clinic. Assay sensitivity and precision (intra- and inter-assay coefficients of variation) were evaluated alongside longitudinal cycle tracking.
What was found
The RIA demonstrated a sensitivity of 7 pg per assay tube, with intra-assay and inter-assay coefficients of variation not exceeding 11.0% and 8.0%, respectively. In normal cycles, salivary progesterone was low during the follicular phase (<100 pmol/L), began rising on day 12, peaked between 230 and 550 pmol/L on day 21, and declined to generally <170 pmol/L by the onset of menses. Saliva was also evaluated in 3 infertility patients.
Why it matters
This study demonstrated that non-invasive daily saliva sampling can detect physiological progesterone fluctuations throughout the menstrual cycle, offering an alternative to frequent venipuncture for monitoring ovarian function.
Limits
The sample size is very small, involving only 13 normal women and 3 clinical patients. Detailed longitudinal clinical outcomes and diagnostic accuracy metrics for the infertility patients are not quantified in the abstract, and the provisional normal reference range was derived from a very limited cohort.
Cited by
- supports In a 28-day menstrual cycle, progesterone levels reach their peak around day 21 or 22.