I have recently had a discussion with an Endocrinologist concerning the
diagnosis of Cushing's Syndrome and the cut-off values for the low dose
dexamethasone test (LDDST).
The cut-off we have used for the LDDST at 0900 hours after 48 hours of
dexamethasone at 2 mg/day is 150 nmol/L for serum cortisol. We measure serum
and urine cortisol on the Immulite 2000. .
A number of references eg Perry et al Ann Clin Biochem 1997;34:345-359 state
that a normal suppression should be < 50 nmol/L but they do not state the
method that has been used to define this value.
Do many labs use this value?
What cut-offs are used for urine free cortisol?
Does any lab have values derived for the Immulite 2000?
John
Dr John Beilby
Senior Biochemist
Clinical Biochemistry
PathCentre
Locked Bag 2009
Nedlands
Western Australia 6009
Tel 61 8 9346 2368 Fax: 61 8 9346 3882
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