Direct assay for progesterone in saliva: comparison with a direct serum assay

Direct assays have been described for the estimation of progesterone in serum and saliva. Both methods showed good inter-assay precision over a year, and the serum assay is now being used routinely in clinical laboratories. A highly significant correlation was obtained for progesterone concentrations in matched serum and saliva samples over a wide range of concentrations. The concentrations of progesterone in daily samples taken through the menstrual cycle fell within the range quoted in previous studies. The benefits of direct saliva measurement are described with reference to the long-term assessment of irregular cycles. Care in sample collection is necessary since contamination with agents such as oral cosmetics may result in overestimation of progesterone concentrations.