ESPE Abstracts

Background: The Short Synacthen Test (SST) is the most popular test of adrenal insufficiency (AI) worldwide. The current SST protocol at Sheffield Children’s Hospital (SCH), UK, recommends measurement of serum cortisol at baseline, then 30- and 60-minutes post stimulation, with a peak cortisol of >429nmol/l constituting a pass. Our practice has evolved to consider near-pass results as “borderline” and patients may be treated with stress dosing steroids only, rather than full replacement.

Methods: We conducted a retrospective analysis of all SSTs performed at SCH from 2011-2019. The number of SSTs performed annually, test indication, Synacthen dose administered (low: 1 mg or standard: 145mcg/m2), cortisol results, timing of peak cortisol, patient’s steroid history and management outcome were extracted from laboratory records and patient notes. A peak cortisol between 350 and 429 nmol/l was categorised as borderline.

Results: We analysed 1275 SSTs over the nine-year period. The number of SSTs being performed annually has increased 54%, from 114 to 175, but the incidence of AI has remained constant (~40 cases/year). Over the study period the proportion of SSTs performed to diagnose steroid induced adrenal suppression increased from 34% to 58%, with 47.4% passing the SST and 15.6% considered borderline. The proportion of tests performed using the standard dose (SDSST) has increased annually from 26% at the start of the study period to 100%. Timing of peak cortisol was dependant on SST dose: 58% of low dose SSTs peaking at 30mins and 96% of SDSSTs at 60mins. Sampling only at 60mins during the SDSST would have resulted in two additional failed SSTs (both in the borderline category), but a cost saving of ~£1000/year. Peak cortisol results were borderline in 122 (9.6%) patients. This proportion remained relatively constant over the study period (mean 9.7%, range 5.4%-15.0%). Management of “borderline” patients depended on the clinical scenario; with their pre-test probability for AI, cortisol result, and steroid history all playing a role. Use of stress-dosing rather than full steroid replacement has not resulted in any adverse events to date.

Discussion: Our SST requests, Synacthen dose and interpretative practice have evolved over the last decade. The number of SSTs conducted each year continues to increase without a change in the incidence of AI. Our data suggest this is due to increasing concern about adrenal suppression secondary to steroid use, however there was a low diagnostic yield of AI requiring replacement glucocorticoid for this indication