Endocrine Abstracts

Aim: In light of recent publications - could a lower cortisol cut off value of ~350 nmol/l be used to safely rule out adrenal insufficiency (AI) compared to current local guideline cutoff value of either a baseline or 9am cortisol of 420 nmol/l? If so could this potentially help reduce the number of Co-syntropin stimulation tests (CST) performed?

Background: Current local guidelines recommend a cortisol cut value of 420 nmol/l to rule out adrenal insufficiency. If values are lower than this cut off then a CST is recommended if adrenal insufficiency is suspected. A recent retrospective study (n = 393) has shown that using a baseline cortisol level of > 354 nmol/l as a cut off is 100% sensitive in ruling out AI whilst other studies have even suggested a lower cut off.

Methods: Retrospective review of medical records of all CSTs performed as a day case over a period of 12 months.

Results: Based on logistic regression on the data from 106 patients, we have NOT identified a lower safe cut off. The statistically lowest cortisol value with 100% specificity of ruling out adrenal insufficiency was 325nmol/l (error range of 325 to 357 nmol/l).

Limitations: All tests were done as outpatients and therefore should not be applied to the inpatient setting. No distinction was made between primary and secondary adrenal insufficiency in our review.

Conclusions: Our data supports published data giving local validity to a cortisol cut off of ~350 nmol/l in outpatients for ruling out adrenal insufficiency.