Oral Presentation ESA-SRB-ANZBMS 2024 in conjunction with ENSA

Stimulating discussion: Basal cortisol as a predictor of passing Short Synacthen Test and the utility of the 60-minute post-stimulation cortisol (#210)

James D Nolan 1 , Suzanne Brown 1 , David Henley 1 2 , Ee Mun Lim 1 3
  1. Department of Endocrinology and Diabetes, Sir Charles Gairdner Hospital, Perth, WA, Australia
  2. Medical School, The University of Western Australia,, Perth, WA, Australia
  3. Department of Biochemistry (QEII), PathWest Laboratory Medicine Western Australia, Perth, WA, Australia

The aim of this study was to identify the basal cortisol (BC) predictive of adrenal sufficiency (AS) as assessed by response to Short Synacthen test (SST) and to evaluate the utility of both 30- and 60-minute stimulated cortisol measurements.

This retrospective, observational, cross-sectional study, analysed all SST results received by PathWest, Perth, Western Australia over a two-year period spanning January 2018 to December 2019 in eligible inpatients and outpatients. BC was obtained prior to intramuscular injection of Synacthen 250 mcg and stimulated cortisol was measured at 30 and 60-minutes. AS was defined as serum cortisol >430 nmol/L at 30-minutes and/or >500 nmol/L at 60 minutes by the Abbott Immunoassay platform. BC threshold required for >95% specificity in predicting AS was determined from Receiver Operating Characteristic (ROC) analysis.

Of the 1216 SSTs performed, 704 results were analysed after applying exclusion criteria. Overall, 583 (81%) patients passed the SST. A BC of ≥335 nmol/L predicted AS at either 30 or 60-minute intervals (Table 1). A lower threshold of ≥240 nmol/L achieved similar specificity in the subgroup of patients with pituitary pathology. On this basis, 219 (31.1%) of SSTs could have been avoided. Where BC was measured after 0945hr, a serum cortisol ≥251 nmol/L predicted AS with >95% specificity. 19 subjects (2.6%) passed the SST solely based on the 60-minute cortisol result. In this group, median cortisol at 30-minutes was 420nmol/L, close to the threshold for AS. Electronic medical records were reviewed, with a minimum follow up period of 4 years, with no evidence of long-term steroid prescription, diagnosis of AI or adrenal crisis.  

A BC of ≥335 nmol/L, and ≥240 nmol/L in patients with pituitary pathology, predicted AS in a large Western Australian cohort. 60-minute post-stimulation cortisol identified an additional 19 patients (2.6%) with AS who would have otherwise failed SST.66b4ce51538e0-ESA_submission_table1.png