M. Pura et al. (Lubochna and Prague) with the title : “The low dose (1 μg) Cosyntropin test (LDT) for Primary Adrenocortical Insufficiency: Defining the normal cortisol response and report on first patients with Addison Disease confirmed with LDT” (ECED 2010; 118: 151–157)

Abstract

I would have thought that the Low Dose tetracosactin Test (LDT) is dead, but now and then transient resurrections do occur. In 1998 we compared normal plasma cortisol responses to 1 μg and 250 μg tetracosactin (Synacthen®, Cosyntropin®) in 35 healthy subjects. We found 19.4 μg/dl (535 nmol/l) to be the lower cutoff response (mean minus 2 standard deviations) for the LDT and 22.5 μg/dl (621 nmol/l) for the 250 μg-test (high dose test – HDT) 30 min after tetracosactin injection. The responses 60 min after injection are markedly different between the tests, because serum cortisol decreases after 30 min in the LDT, but further rises in the HDT [1]. In the same paper we compared the two tests with the results of insulin hypoglycaemia tests or metyrapone tests in 40 patients with pituitary disease with regard to the presence or absence of secondary adrenal insufficiency. By using the different lower cutoff points of the two tetracosactin tests we found that both provided exactly the same information, and both tests were unable to detect mild forms of secondary adrenal insufficiency. Using our original data and the ROC method of analysis, Dorin et al. confirmed our results and conclusions [2].