Radioimmunoassay of progesterone in saliva: a simplified technique using 125I-radioligand

The value of serial salivary progesterone (P) determinations for evaluation of corpus luteum function compared with sporadic serum samplings is recognized. Salivary P concentrations have previously been determined by a relatively difficult assay which utilizes a tritiated radioligand. The present study was designed to compare this conventional method with a simpler assay utilizing an iodinated radioligand. The values obtained with two different radioimmunoassay (RIA) systems were compared for samples collected throughout the luteal phase of seven normal menstrual cycles and three conception cycles. In the seven nonconception luteal phases as well as in the three conception luteal phases, daily salivary P determinations by the two techniques correlated significantly with each other (r = 0.56; P less than 0.001). For the seven nonconception luteal phases, the salivary P determinations obtained by 125I RIA (Saliva 125I) correlated significantly with the matched serum values (r = 0.54; P less than 0.001). However, the correlation was poor between the salivary P determinations obtained by the 3H RIA (Saliva 3H) and the matched serum values. The simplicity and accuracy of the 125I RIA and the convenience of saliva sampling provide a practical approach to monitor human luteal function.