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The Low Dose ACTH Stimulation Test: Is 30 Minutes Long Enough?
Endocr Pract. 2015 Feb 9;:1-21
Authors: Cartaya J, Misra M
Abstract
Objective: Controversy persists regarding the use of the low dose ACTH stimulation test (LDST) for the diagnosis of adrenal insufficiency as well as the optimal interpretation of the results of the test. However, many centers are now using the LDST to assess adequacy of cortisol secretion, and some use only a 30 minute cortisol level to determine adrenal sufficiency or insufficiency. This study examined both a 30 and 60 minute cortisol level to assess whether the interpretation of the test was affected when both cortisol levels were taken into consideration. Design: Data were obtained by retrospective chart review from a single pediatric endocrinology unit over a 7 year period.Patients: 82 patients who completed the LDST were identified. Patients had a mean age of 11.7 years; 37% were female.Measurements: Cortisol levels were evaluated at baseline, 30 and 60 minutes post administration of Cosyntropin. A cut off of ≥18 μg/dL was used to define adrenal sufficiency.Results: 54% of patients reached peak cortisol levels at 60 minutes and 11 patients who did not pass the test at 30 minutes, did so at 60 minutes. The only predictive characteristic was weight status such that overweight and obese individuals tended to peak at 30 minutes and normal and underweight individuals tended to peak at 60 minutes.Conclusion: Although further studies are necessary to confirm our findings, it appears that measuring cortisol both 30 and 60 minutes following administration of synthetic ACTH may be necessary to avoid overdiagnosis of adrenal insufficiency.
PMID: 25667371 [PubMed - as supplied by publisher]
I spent a couple years trying to get our lab to only run 60 minute post ACTH levels, knowing that 60 minute levels are usually higher than 30 minute (confirmed by many studies). Then I went back to the primary literature and found that only the 30 minute level was tested against insulin tolerance test (gold standard) (Lindholm J Clin Endo 1987). In a subsequent paper by Hurel (J Clin Endo 95) , 30 and 60 m were compared to ITT and 30 min showed better correlation. Of note Hurel used higher cut-off for 60 m vs 30 m.
I think now that the best approach is to use only 30 m. Including 60 m likely leads to UNDERdiagnosis of AI, contrary to the authors conclusion.