A Faster Radioimmunoassay of Progesterone in Plasma, with Use of Polyethylene Glycol as Precipitant

We report a reliable radioimmunoassay for plasma pro-gesterone in which polyethylene gtycol (“Carbowax 6000”) is used to separate antibody-bound and free hormone. initially, progesterone is concentrated by putting the sample through a column of LH-20 Sephadex. Procedural losses in each sample are not monitored. We compared the reliability and practicality of this method with that of another method in which procedural losses are monitored for each sample; accuracy and precision were similar. Our method saves technical assay time and scintillation counter space and time without sacrificing reliability. Steroid radioimmunoassays are often highly specific only after preliminary purification of the sample. Celite (1-3), LH-20 Sephadex (4-6), hydroxyalkoxypropyl Sephadex (7), and alumina column- (8) and alumina thin-layer (9) chromatographic methods have been used to purify progesterone.1 Analytical recovery of steroid varies among samples, and many investigators monitor the procedural losses. This adds to the complexity, time, and cost of the assay. Here, we describe a radioimmunoassay for plasma progesterone in which LH-20 Sephadex is used for sample purification and procedural losses are not monitored in every sample. We compare the reliability and practicability of this radioimmunoassay with an-other in which procedural losses are monitored in every sample. In addition, we report the first radioimmu-noassays in which polyethylene glycol is used to separate antibody-bound and free progesterone