Endocrine Abstracts

Background: The Short Synacthen test (SST) is commonly used in clinical practice to evaluate adrenal function. Appropriate patient selection for SST is needed to ensure accurate interpretation of the results and to mitigate increased healthcare costs associated with unnecessary testing and inappropriate glucocorticoid (GC) steroid replacement. This study aimed to investigate the indications of inpatient SSTs over a one-year period, to determine the accuracy of testing.

Method: We reviewed all relevant clinical information of all the inpatient SSTs performed between 28th February 2022 and 28th February 2023 at our institution. An SST test was considered appropriate if patients presented with symptoms suggestive of adrenal insufficiency (AI), and inappropriate if no clear indication was provided or the patient’s clinical history and presenting features did not suggest AI.

Results: 457 patients, with a median age of 67 years (IQR 56 to 76.5 years) underwent 485 inpatient SSTs. The common indications for SSTs were: postural hypotension (36.70%), hyponatremia (17.1%), hypotension (16.3%) and previous or current exogenous GC use (8.1%). Of those who underwent SSTs for postural hypotension, 89.9% were symptomatic and 10.1% were asymptomatic. Of those who presented with hyponatremia, 6% had symptoms suggestive of AI and an initial presenting sodium of 127 nmol/l (IQR 124 nmol/l - 130 nmol/l). 27.9% of the patients who had hypotension had ongoing infection; 30.4% had persistent low blood pressure suggestive of AI and 33.0% had a transient hypotensive episode. 4.5% of the SSTs were carried out due to subjective feelings of giddiness and lethargy and 5.6% of SST had no documented indications. Of the 485 inpatient SSTs, 74/485 (15.3%) did not have a prior morning cortisol. 228/485 (47.0%) of SSTs did not have a measured paired baseline ACTH. Nearly half (49%) of the SSTs were performed in patients who did not have features suggestive of AI. 28 SSTs were repeated due to incorrect initial tests. Of those who underwent SSTs for suspected features of AI, 65.4% had a normal SST result. Similarly, in those who underwent SST where there was no indication for AI, 62.5% had a normal result.

Conclusion: A majority of the inpatient SSTs were inappropriately indicated. Our study demonstrates that presenting features for SST testing do not reliably predict SST outcomes in our cohort. Common errors identified insufficient pre-test cortisol testing and lack of concomitant ACTH measurement. We advocate judicious patient selection for SST testing to avoid inappropriate use of SST and subsequent life-long need for GC replacement.