Spurious Overestimation of Plasma Cortisol in Patients with Chronic RenalFailure*

Publisher Website
Google Scholar
Abstract
Plasma cortisol concentrations in patients with chronic renal failure were measured by 5 different radioimmunoassays, 4 commercial methods and an in-house method after paper chromatography. Cortisol concentrations of the same samples measured by the various methods did not agree. The difference was attributed to cross-reactivity of the antisera with steroids and glucuronide conjugates which circulate at high concentrations in patients with chronic renal failure. With 2 of the methods, values were higher in unextracted plasma (P < 0.001) than after paper chromatography (in-house procedure). The values obtained with the other 2 methods were not significantly different from those obtained by the post-paper chromatography method for baseline and post-dexamethasone samples. Plasma cortisol values after metyrapone administration were much higher when measured by any of the 4 commercial assays than after paper chromatography. A simple dichloromethane extraction improved the results from 1 method. Laboratories are encouraged to assess carefully the behavior of cortisol antisera before using them in the assay of plasma cortisol concentrations in patients with chronic renal failure.