I. ADHB samples:
a. Specimens requesting for " Cortisol - post Dexamethasone suppression test" will have a test add for dexamethasone level if the cortisol from the same specimen is >=50nmol/L.
b. Specimens requesting for "Dexamethasone level" will have dexamethasone reported. Cortisol will not be reported unless specifically requested.
II. Samples from outside LabPlus :
Specimens requesting for " Dexamethasone level" will have dexamethasone reported separately from cortisol results measured by other laboratories.
Units: nmol/L
Uncertainty of measurement: 12%
Dexamethasone is an exogenous steroid compound thus normally it should not be detectable in circulation. The detection limit of the assay for dexamethasone is 0.3nmol/L
In the setting of 1mg overnight dexamethasone suppression test, our in-house evaluation suggests that a dexamethasone level <3.1nmol/L from the plasma sample collected the next morning (8-10am) may not be sufficient to cause full suppression of morning cortisol to below 50nmol/L in some healthy individuals (see diagnostic use and interpretation section).
Principle : Liquid Chromatography Mass Spectrometry (LCMS)
Dexamethasone is a synthetic corticosteroid with potent glucocorticoid activity. Its anti-inflammatory and immunosuppressive effects have been utilised for the treatment of many medical conditions. Therapeutic drug monitoring is generally not useful or necessary as its pharmacodynamic effect is not well reflected by circulating blood level and its efficacy/side effects can be monitored through clinical or other biochemical parameters.
Occasionally, dexamethasone level can be useful to identify patients with iatrogenic Cushing's syndrome (with or without typical clinical features) from use of exogenous dexamethasone containing products causing otherwise unexplained low plasma cortisol from secondary glucocorticoid insufficiency.
In the setting of 1mg overnight dexamethasone suppression test, testing dexamethasone level can aid interpretation particularly if the cortisol level is not adequately suppressed i.e. >=50nmol/L. Our in-house evaluation suggests dexamethasone <3.1nmol/L from the plasma sample collected the next morning (8-10am) may not be sufficient to cause full suppression of cortisol in some healthy individuals.
Emails to chemicalpathologist@adhb.govt.nz will receive priority attention from the on-call chemical pathologist.
If the query concerns a specific patient please include the NHI number in your email.
If email is not a suitable option, please contact the on-call chemical pathologist via Lablink (Auckland City Hospital ext. 22000 or 09-3078995).
Individual chemical pathologists may be contacted but will not be available at all times.
After-hours : contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours.
Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
Dr Cam Kyle: CampbellK@adhb.govt.nz ext 22052
Dr Weldon Chiu: WeldonC@adhb.govt.nz ext. 23427
Dr Campbell Heron: CHeron@adhb.govt.nz ext. 23427
Centrifuge and separate blood as soon as possible after collection.
If sending within Auckland then sample can be sent refrigerated (2-8 degrees) or at ambient temperature (8-24 degrees).
If sending from outside Auckland then send sample refrigerated (2-8 degrees).
Note: If temperature during shipping is likely to exceed 24 degrees then results may not always be reliable.