BACKGROUND:
Cushing's syndrome is a
state of
hypercortisolism manifesting non-specific clinical; features where its
diagnosis entails biochemical confirmation of
cortisol excess. this study aims to validate the
efficacy of midnight salivary
cortisol as a
screening test for Filipino suspected with
Cushing's syndrome and determine the cut-off value applicable in the local setting.
METHODS:
This is a
cross-sectional study of Filipinos suspected with endogenous
Cushing's syndrome seen at a
tertiary hospital. Modification of
plasma cortisol measured by RIA was used to
measure salivary
cortisol. The
sensitivity,
specificity, positive predictive curve, negative predictive curve and area under the
screening tests were estimated and compared using 48 hour low
dose dexamethasone suppression test (LDDST) as the
reference standard.
RESULTS:
The determine cut-off value (? 7.0 nmol/L) for salivary
cortisol showed a relatively high
sensitivity (91.3%) and
specificity (89.5%) in detecting cases suspected of
Cushing's syndrome. One milligram (1mg)
dexamethasone suppression test had the highest
sensitivity (100%) but had the lowest
specificity (68.4%) as a
screening test. The area under the curve of the three
diagnostic test appeared to be
similar when compared with the low
dose dexamethasone suppression test.
CONCLUSIONS:
Using a cut-off value of 7nmol/L, local utility if late-night salivary
cortisol has a high
sensitivity and specificity in detecting
Cushing's syndrome. It has a
similar efficiency with 24-hour
urine free
cortisol and 1mg
dexamethasone suppression test as a
screening test for
Cushing's syndrome. Salivary
cortisol may be considered as a valid initial
screening test for Filipinos suspected of
cushing's syndrome.