From the Guidelines
The LDDST protocol involves administering 0.5 mg of dexamethasone 6-hourly (09:00,15:00,21:00,03:00 h) for 48 h, with serum cortisol level measured at 0,24, and 48 h, as recommended in the consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence 1. The low-dose dexamethasone suppression test (LDDST) is a crucial diagnostic tool for Cushing's syndrome, and its protocol is well-established in the medical literature.
- The test is used to confirm the diagnosis of Cushing's syndrome and to differentiate between various causes of hypercortisolism.
- The LDDST protocol involves administering 0.5 mg of dexamethasone 6-hourly for 48 h, with serum cortisol level measured at 0,24, and 48 h, as recommended in the consensus guideline for the diagnosis and management of pituitary adenomas in childhood and adolescence 1.
- The dose for patients weighing <40 kg is 30 μg/kg per day, and the serum cortisol level is measured at 0,24, and 48 h 1.
- The diagnostic cut-off for the LDDST is >=50 nmol/l (>=1.8 μg/dl), with a sensitivity of 95% and specificity of 80% 1.
- It is essential to note that the LDDST protocol may vary depending on the patient's weight and other factors, and it is crucial to follow the recommended guidelines to ensure accurate results.
- The test works by suppressing ACTH production in the pituitary gland, which should normally lead to decreased cortisol secretion from the adrenal glands.
- In healthy individuals, the low dose of dexamethasone will suppress cortisol production, resulting in low cortisol levels after the test.
- However, in patients with Cushing's syndrome, cortisol levels remain elevated despite dexamethasone administration, indicating resistance to negative feedback.
- Blood for cortisol measurement is typically drawn at specified times, and patients should avoid medications that can affect dexamethasone metabolism for at least one week before the test to ensure accurate results.
From the Research
Dexamethasone Suppression Test Protocol
The protocol of dexamethasone suppression test involves administering dexamethasone in various doses and frequencies to assess cortisol levels.
- The low-dose overnight dexamethasone suppression test (LDODST) is commonly used to diagnose hypercortisolism in patients suspected to be suffering from Cushing's syndrome (CS) 2.
- The test typically involves administering 1 mg of dexamethasone overnight, and then measuring plasma cortisol levels the next morning 3, 4.
- However, the specific protocol of administering 0.5 mg of dexamethasone every 12 hours for a few days prior to measuring cortisol is not mentioned in the provided studies.
- Other studies have used different protocols, such as administering 8 mg of dexamethasone overnight 5, or 0.01 mg/kg or 0.015 mg/kg of dexamethasone intravenously 6.
Variations in Dexamethasone Suppression Test Protocols
- The studies demonstrate variations in the dexamethasone suppression test protocols, including different doses and administration routes 3, 5, 4, 6.
- The choice of protocol may depend on the specific clinical context and the population being tested.
- The provided studies do not mention a protocol involving 0.5 mg of dexamethasone every 12 hours for a few days prior to measuring cortisol, suggesting that this specific protocol may not be commonly used or studied.