From the Guidelines
A STIM test with a baseline cortisol of 19 and ending cortisol of 31 is considered normal, as it indicates a sufficient response to stimulation, with the increase in cortisol levels exceeding the typical threshold for a normal response. This result suggests that the adrenal glands are functioning properly and can produce adequate amounts of cortisol in response to stress. According to the guidelines for the diagnosis and management of critical illness-related corticosteroid insufficiency (CIRCI) in critically ill patients, a peak cortisol level above 18-20 μg/dL is typically considered normal 1. In this case, the baseline cortisol level is 19, and the ending cortisol level is 31, representing a rise of 12 points, which is well above the expected increase of at least 7-10 μg/dL from baseline.
The ACTH stimulation test is used to assess the function of the hypothalamic-pituitary-adrenal (HPA) axis, and a normal response indicates that the adrenal glands can produce cortisol in response to stimulation. The test involves administering synthetic ACTH (usually cosyntropin/Synacthen) to stimulate the adrenal glands, and then measuring the resulting cortisol levels. The fact that the cortisol levels increased significantly in response to stimulation suggests that the HPA axis is functioning properly.
Some key points to consider when interpreting the results of a STIM test include:
- The baseline cortisol level, which in this case is 19
- The peak cortisol level, which in this case is 31
- The increase in cortisol levels from baseline to peak, which in this case is 12 points
- The laboratory reference range for normal cortisol levels, which may vary depending on the specific laboratory and assay used. As noted in the guidelines, the high-dose (250-μg) ACTH stimulation test is considered superior to other existing diagnostic tests for establishing the diagnosis of primary adrenal insufficiency, with peak cortisol levels below 18 μg/dL indicating adrenal insufficiency 1. However, in this case, the results of the STIM test suggest that the adrenal glands are functioning normally.
From the Research
Adrenal Insufficiency Diagnosis
- The diagnosis of adrenal insufficiency is clinically challenging and often requires ACTH stimulation tests 2.
- The ACTH stimulation test is commonly performed in patients suspected of having adrenal insufficiency when the basal serum cortisol levels are inconclusive 3.
Interpretation of STIM Test Results
- For interpretation of an adrenocorticotropin test, only peak - and not delta - cortisol should be used 4.
- The use of basal cortisol levels can help predict adrenal insufficiency, with levels ≤100 nmol/L having a high positive predictive value and levels ≥450 nmol/L having a high negative predictive value 5.
Normal Cortisol Levels
- There is no specific mention of normal cortisol levels in the provided studies, but it can be inferred that a basal cortisol level of 19 and an ending cortisol level of 31 may not be sufficient to rule out adrenal insufficiency without considering other factors such as the patient's clinical presentation and the type of ACTH stimulation test used 3, 5.
- The diagnostic accuracy of the ACTH stimulation test can be affected by various factors, including the time of day the test is performed, the type of assay and sample source used for cortisol measurement, and the clinical presentation of the patient 3, 2.