The combined low-dose dexamethasone suppression corticotropin-releasing hormone test as a tool to rule out Cushing's syndrome.
OBJECTIVE
It remains to be evaluated whether the combined low-dose dexamethasone suppression corticotropin-releasing hormone test (LDDST-CRH test) may add to the diagnostic approach of patients suspected to have Cushing's syndrome (CS). The aim of the present study was to evaluate whether the LDDST-CRH test may have a place in the diagnostic strategy of CS.


METHODS
Prospective evaluation of a consecutive series of patients with suspected CS from 2004 to 2006.


METHODS
All the subjects underwent the same screening protocol including 1 mg dexamethasone suppression test, 24-h urinary free cortisol (UFC), and midnight serum cortisol, followed by the LDDST-CRH test whose results were not used to establish a definitive diagnosis. Plasma dexamethasone concentration was measured 2 h after the last dose of dexamethasone. Patients qualified for CS when at least two screening tests were positive.


RESULTS
Sixteen patients had CS while in the remaining 15 subjects CS was excluded. Even if not statistically significant, the sensitivity and the negative predictive value of the cortisol 15 min after CRH were better than the other tests; on the other hand, the test specificity was lower. All of the patients classified as indeterminate were correctly diagnosed by the LDDST-CRH test. Nevertheless, the repeated assessment of the screening tests and the active follow-up gave the same correct results. In all of the patients misclassified by the LDDST-CRH test, the plasma dexamethasone concentrations were in the normal range.


CONCLUSIONS
Based on our findings, we suggest that the LDDST-CRH test may still find a place as a rule-out procedure in patients who present with indeterminate results after screening and may be unavailable to repeat testing during follow-up.
Reimondo
Giuseppe
G
Dipartimento di Scienze Cliniche e Biologiche, Medicina Interna I, Università di Torino, ASO San Luigi, Regione Gonzole, 10, 10043 Orbassano, Italy. giuseppe.reimondo@unito.it
Bovio
Silvia
S
Allasino
Barbara
B
De Francia
Silvia
S
Zaggia
Barbara
B
Micossi
Ilaria
I
Termine
Angela
A
De Martino
Francesca
F
Paccotti
Piero
P
Di Carlo
Francesco
F
Angeli
Alberto
A
Terzolo
Massimo
M
D000293:Adolescent; D000308:Adrenocortical Hyperfunction / Q000175:diagnosis; D000328:Adult; D000368:Aged; D003346:Corticotropin-Releasing Hormone / Q000008:administration & dosage; D003480:Cushing Syndrome / Q000175:diagnosis*; D003907:Dexamethasone / Q000008:administration & dosage; D003940:Diagnostic Techniques, Endocrine; D005260:Female; D005938:Glucocorticoids / Q000008:administration & dosage; D006801:Humans; D008297:Male; D008875:Middle Aged; D011446:Prospective Studies; D012372:ROC Curve; D012680:Sensitivity and Specificity
D005938:Glucocorticoids; D003907:Dexamethasone; D003346:Corticotropin-Releasing Hormone