The short cosyntropintest revisited - new normal reference range using LCMSMS.

The short cosyntropintest revisited - new normal reference range using LCMSMS.

J Clin Endocrinol Metab. 2018 Feb 14;:

Authors: Ueland GÅ, Methlie P, Øksnes M, Thordarson HB, Sagen J, Kellmann R, Mellgren G, Ræder M, Dahlqvist P, Dahl SR, Thorsby PM, Løvås K, Husebye ES

Abstract
Background: The cosyntropin test is used to diagnose adrenal insufficiency (AI) and non-classical congenital adrenal hyperplasia (NCCAH). Current cutoffs for cortisol and 17-hydroxyprogesterone (17-OHP) are derived from non-standardized immunoassays. Liquid chromatography tandem mass spectrometry (LCMSMS) offers direct measurement of steroids, prompting the need to re-establish normal ranges.
Aim: Define cutoff values for cortisol and 17-OHP in serum by LCMSMS 30 and 60 minutes after intravenous administration of 250 µg tetracosactide acetate (Synachten©) to healthy volunteers, and compare LCMSMS with routine immunoassays.
Methods: Cosyntropin testing of healthy subjects (n=138) and patients referred for evaluation of adrenocortical function (n=94). Steroids were assayed by LCMSMS and compared with two immunoassays used in routine diagnostics (Immulite and Roche platforms). Cutoff level for cortisol was defined as the 2.5% percentile in healthy subjects not using oral estrogens (n =121), and for 17-OHP as the 97.5% percentile.
Results: Cortisol cutoff levels for LCMSMS were 412 and 485 nmol/L at 30 and 60 minutes, respectively. Applying the new cutoffs, 13/60 (22%) who had AI according to conventional criteria, now had a normal test result. For 17-OHP the cutoff levels were 8.9 and 9.0 nmol/L at 30 and 60 minutes, respectively.
Conclusions: Using LCMSMS, cutoff levels for cortisol and 17-OHP after cosyntropin stimulation are lower than those based on immunoassays, possibly since cross-reactivity between steroid intermediates and cortisol is eliminated. This reduces the number of false positive tests for AI and false negative test for NCCAH.

PMID: 29452421 [PubMed - as supplied by publisher]

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