What is the value of the 60-minute cortisol measurement in the short synacthen test (SST)? Evidence for the defence

Diagnosis and management of adrenal insufficiency

Adrenal insufficiency is the inadequate secretion of glucocorticoid and/or mineralocorticoid secretion from the adrenal cortex. Primary adrenal insufficiency is the result of failure of the adrenal gland and secondary adrenal insufficiency is due to a lack of stimulation via pituitary adrenocorticotropic hormone or hypothalamic corticotropin-releasing hormone. Adrenal insufficiency may cause non-specific symptoms. Early detection and testing based on clinical suspicion may prevent subsequent presentation with adrenal crisis. Once identified, a low baseline cortisol (often <100 nmol/L) alongside raised adrenocorticotropic hormone (ACTH) can be enough to diagnose primary adrenal insufficiency. However, confirmatory testing can be done using the cosyntopin (Synacthen®) stimulation test or the insulin tolerance test, which is the gold standard for secondary adrenal insufficiency. The underlying cause of adrenal insufficiency can often be identified via a strategic approach to investigation. Adrenal crisis is a life-threatening medical emergency which must be treated immediately if there is strong clinical suspicion with fluids and corticosteroids otherwise can be fatal. Patients must be educated and empowered to take control of their own medical management.

The short synacthen test: Variations in methodology and protocols in KSA

Objectives

This study aimed to compare the current Kingdom-wide practice with our prior institutional study on use of the short synacthen test (SST), and to determine whether physician specialty or grade is associated with a tendency toward using a particular protocol.

Method

We surveyed clinicians registered with the Saudi Medical Council to determine the different SST protocols used within KSA.

Results

We received 162 responses, 66 (41%) from endocrinologists and the remainder from internists. A total of 61 (38%) respondents were consultants, whereas the rest were non-consultant grade. The clinicians indicated metabolic derangements, such as hypotension (78%), hyponatremia (65%), hypoglycemia (59%), and hyperkalemia (54%), as the main reasons for performing the test. Most clinicians used the SST protocol, which measures baseline serum cortisol (90%) and ACTH (78%) on the test day. A total of 75% of the physicians measured both the 30- and 60-minute serum cortisol after ACTH injection. Of these clinicians, 13% reported that the cortisol levels were below the pass threshold at 30 min but reached the pass threshold only at 60 min. The SST was normal 90% of the time when performed. A total of 93% of the clinicians considered a stimulated cortisol level of 550 nmol/L to be the threshold for normal adrenal function.

Conclusion

The survey confirms that 60-min serum cortisol should be part of the SST protocol to avoid false-positive results. Moreover, clinicians should consider other causes of these metabolic derangements before requesting a SST, particularly in patients with a low pretest probability.