Objective: To compare the total plasma cortisol values obtained from three widely used immunoassays and a high pressure liquid chromatography (HPLC) technique on samples obtained from patients with sepsis.
Design and setting: Observational interventional in the general intensive care unit of a metropolitan hospital
Patients and participants: Patients admitted to the intensive care unit with a diagnosis of sepsis and fulfilling criteria of systemic inflammatory response syndrome.
Interventions: Standard short synacthen test performed with 250microg cosyntropin.
Measurements and results: Two of the three immunoassays returned results significantly higher than those obtained by HPLC: Immulite by 95% (95%CI 31-188%) and TDx by 79% (21-165%). The limits of agreement for all three immunoassays with HPLC ranged from -62% to 770%. In addition, by classifying the patients into responders and non-responders to ACTH by standard criteria there was concordance in all assays in only 44% of patients.
Conclusions: Immunoassay estimation of total plasma cortisol in septic patients shows wide assay related variation that may have significant impact in the diagnosis of relative adrenal insufficiency.