Hyperadrenocorticism – Diagnostic Testing Flashcards
• What is sensitivity?
The proportion of individuals with disease who are correctly identified as having disease – minimize false negatives
• What is specificity?
The proportion of individuals without disease who are correctly identified as not having disease – minimize false positives
• What are the two steps to diagnosing HAC?
Screening step & differentiation step
• List the screening tests available
ACTH stimulation test, low dose dexamethasone suppression test, urine cortisol:creatinine ratio, combined dexamethasone suppression/ACTH stimulation test
• How does an ACTH stimulation test work?
The adrenal glands have become enlarged, therefore on administering ACTH a larger rise in plasma cortisol levels is seen in patients suffering from HAC compared to normal
If the HAC is iatrogenic there baseline cortisol levels will not change throughout the test (remain low)
• Can a LDDST differentiated between ADH and PDH?
Sometimes, if cortisol levels fall but do not suppress it could be either, if they suppress and escape it is PDH, if they remain high it is ADH
• When would you use a urine cortisol: creatinine ration?
Low suspicion, trying to rule out HAC
• List the differentiation tests available
LDDST, HDDST, endogenous ACTH, imaging of pituitary or adrenal glands, combined dexamethasone suppression/ACTH stimulation test
• How does a HDDST differentiate between ADH and PDH?
If it is PDH cortisol levels will suppress (<40nmol/l) and remain suppressed, if it is ADH cortisol levels will either fluctuate, or remain high but will not suppress
• In which type of HAC are endogenous ACTH levels at their highest?
PDH
• How do you interpret the combined test results?
Normal – suppression, normal stimulation
PDH – suppression, exaggerated stimulation
PDH or ADH – lack of suppression, normal stimulation
PDH or ADH – lack of suppression, exaggerated stimulation
