How to Perform the Cosyntropin Test for Adrenal Insufficiency
The cosyntropin test is performed by administering 0.25 mg of cosyntropin intravenously or intramuscularly, with blood samples collected at baseline and at 30 and 60 minutes after administration to measure cortisol levels. Walking the patient before the test is not required or part of the standard protocol. 1, 2
Standard Cosyntropin Test Protocol
- Obtain a baseline blood sample for serum cortisol (and ACTH if primary adrenal insufficiency is suspected) before administering cosyntropin 1, 3
- Administer 0.25 mg of cosyntropin via intravenous or intramuscular injection 2
- Collect blood samples for cortisol measurement at 30 minutes and 60 minutes after cosyntropin administration 2, 4
- A peak cortisol level above 18 μg/dL (500 nmol/L) at either 30 or 60 minutes is considered a normal response, ruling out adrenal insufficiency 1, 2
Important Pre-Test Considerations
- Stop glucocorticoids and spironolactone on the day of testing (long-acting glucocorticoids may need to be stopped earlier) 2
- Discontinue estrogen-containing medications 4-6 weeks before testing as they affect cortisol binding globulin levels 2
- No specific activity requirements (like walking) are mentioned in any guidelines or protocols for the test 1, 3, 2
- The test is preferably performed in the morning, although this is not strictly necessary 3
Interpretation of Results
- A peak cortisol level below 18 μg/dL at both 30 and 60 minutes suggests adrenal insufficiency 1, 2
- Measuring cortisol at both 30 and 60 minutes is important as 54% of patients may reach peak cortisol levels at 60 minutes 4
- Some patients who fail to reach adequate cortisol levels at 30 minutes may still show a normal response at 60 minutes 4
- Assay-specific and sex-specific cortisol cut-off values may improve diagnostic accuracy compared to the classic 18 μg/dL threshold 5, 6
Special Considerations
- For suspected primary adrenal insufficiency, the 30-minute cortisol determination is sufficient to establish a diagnosis in over 95% of cases 5
- For suspected central (secondary) adrenal insufficiency, the 60-minute cortisol measurement improves diagnostic accuracy 5
- Weight status may affect timing of peak cortisol response: overweight/obese individuals tend to peak at 30 minutes, while normal/underweight individuals tend to peak at 60 minutes 4
- Never delay treatment in suspected acute adrenal crisis to perform diagnostic testing 1, 3
Pediatric Dosing
- For children aged 2-17 years: 0.25 mg cosyntropin (same as adults) 2
- For children under 2 years: 0.125 mg cosyntropin 2
The cosyntropin test is a standardized procedure with specific timing for blood collection. There is no requirement or recommendation in any guidelines for patients to walk or engage in physical activity before or during the test.