Improved specificity of a new direct assay for urinary cortisol: Application in corticoid treated patients

Twenty four hours urinary free cortisol (UFC) excretion has been determined in 35 eucortisolic control patients, in seven of them before and after tet racosactide (Synacthen(R)) stimulation and in 18 patients treated by anti-i nflammatory steroids. Results of the new direct Immunotech RIA (Dlm) were c ompared to those of the INCSTAR RIA kit with (ECA) or without methylene chl oride extraction (DCA). In controls Dim UFC (106.2+/-45.8 nmol/24h) was sig nificantly lower than DCA UFC (397+/-119 nmol/24h) and than ECA UFG (127+/- 49 nmol/24h). After tetracosactide stimulation, median of DCA/Dlm ratio dec reased from 3.61 to 1.88 whereas ECA/Dlm ratio did not change significantly (1.31 to 1.06). In treated patients most DCA and ECA results were over the upper limit of controls but only 5 Dim results were increased. Dim assay s howed good specificity and practicability and may be used with benefit in t he evaluation of the adrenal gland function.