Endocrine Abstracts

Aim: The short Synacthen test (SST) is an established test used to assess the hypothalamic-pituitary-adrenal axis. There remains debate whether a 30 minute or 60 minute cortisol sample has diagnostic superiority. Currently at the Queen Elizabeth University Hospital, Glasgow all tests arranged by endocrinology are performed by endocrine nurse specialists who utilise a 0 and 30 minute cortisol protocol. Performing a further 60 minute sample requires more nursing time and space resulting in increased cost implications and so our aim was to assess whether performing an additional 60 minute cortisol sample would be worthwhile and alter clinical management.

Method: Patients attending for an SST in May 2018 by the endocrine nurse specialists had samples obtained at 0, 30 and 60 minutes. All patients had a standard protocol for the SST using intravenous Synacthen (250 μg). The current local cut-off value for cortisol at 30 minutes is 430 nmol/l.

Results: 53 SST were performed during May 2018. 8 (15.1%) patients had an inadequate response to Synacthen based on their 30 minute sample. 3 (5.6% of overall group) of these patients had a further rise in their cortisol measurement which gave them an adequate response at 60 minutes (> 430 nmol/l). Of those who had an inadequate response at 30 minutes, 2 were already on hydrocortisone replacement and 1 was undergoing pituitary surveillance; in no case did the 60 minute cortisol sample alter clinical management. No patient with a baseline cortisol <100 nmol/l had an adequate response to synacthen in this audit group.

Conclusions: Assessment of 30 and 60 minute cortisol after Synacthen resulted in discrepant results in only 3/51 cases and did not alter management. We conclude that 60 minute cortisol sampling results in additional resource burdens with no clinical gain.