Improved protein-binding radioassay for plasma cortisol.
We describe an improved competitive protein-binding radioassay for total plasma cortisol, which permits rapid analysis of many samples. Plasma, 0.1 mL, is directly applied to a Whatman 3MM filter-paper strip, which is extracted once with dichloromethane. The extract is evaporated and the residue is assayed directly by the micro-method of Murphy (J. Clin. Endocrinol. Metab. 27: 973, 1967). Comparison with the original Murphy method (ethanol extraction) yielded excellent agreement (r = 0.988). One hundred samples, in duplicate, can easily be assayed at a time.
D006801:Humans; D006854:Hydrocortisone / Q000097:blood*; D011869:Radioligand Assay / Q000379:methods*; D013997:Time Factors
D006854:Hydrocortisone