Endocrine Abstracts

Aim: To establish 9am cortisol predictive value of adrenal insufficiency with normal/abnormal short synacthen tests (SSTs) and whether test indication influences this.

Methodology: • SSTs completed from 01/01/2023 - 30/09/2024 • Beckman assay for cortisol analysis • Electronic patient records used to identify: SST results, pre-test 9am cortisol levels, test indication • SST’s categorised into normal (peak cortisol >450) and abnormal (peak cortisol <450) • 9am cortisol cutoff for completing SSTs <300, although from January - November 2023 it was <350 • Two patients discounted from analysis due to questions about steroids taken pre-SST

Results: • 450 SSTs identified. 32 discounted as lacked pre-test 9am cortisol • 418 results analysed: 355 normal, 63 abnormal • 42 patients with normal SSTs had 9am cortisol <150, 17 of which <100 • 9 patients with 9am cortisol 151-300 had abnormal SSTs • No patients with 9am cortisol >300 had abnormal SSTs

Conclusion: 9am cortisol <150 is a good predictor of abnormal SSTs, however testing is still required to prevent unnecessary overtreating as 45% of SSTs were normal. Equally, 3% of 9am cortisol >151 and <300 were abnormal, so testing for any 9am cortisol <300 remains necessary to prevent missed diagnosis. Categorising SST indications does not demonstrate marked improvement in sensitivity and specificity except predicting normal SST results for GP referred patients.