Discriminatory Value of the Low-Dose Dexamethasone Suppression Test in Establishing the Diagnosis and Differential Diagnosis of Cushing’s Syndrome
Andrea M. Isidori,
Gregory A. Kaltsas,
Shahid Mohammed,
Damian G. Morris,
Paul Jenkins,
Shern L. Chew,
John P. Monson,
G. Michael Besser and
Ashley B. Grossman
Department of Endocrinology, St. Bartholomew’s Hospital, London ECIA 7BE, United Kingdom
Address all correspondence and requests for reprints to: Prof. A. B. Grossman, Department of Endocrinology, St. Bartholomew’s Hospital, London ECIA 7BE, United Kingdom. E-mail: a.b.grossman{at}qmul.ac.uk.
Cushing’s syndrome requires a screening test of high sensitivity,followed by biochemical evaluation of the source of the tumorwhen the cause is ACTH dependent. The high-dose dexamethasonesuppression test is still in common use as an aid in differentialdiagnosis, although its value has been queried. We have routinelyused the low-dose dexamethasone suppression test for many yearsin the diagnosis of Cushing’s syndrome but noticed thatpatients with pituitary-dependent Cushing’s syndrome orCushing’s disease, usually showed some degree of suppressionof their serum cortisol, compared to those with the ectopicACTH syndrome. We therefore analyzed retrospectively the serumcortisol responses during the low-dose dexamethasone suppressiontest and the high-dose dexamethasone suppression test in 245patients with ACTH-dependent Cushing’s syndrome and comparedthe diagnostic utility of each test either alone or in combinationwith a standard test using CRH. Evaluation of the serum cortisolresponse at 24 and 48 h during the low-dose dexamethasone suppressiontest correctly identified 98% of patients with ACTH-dependentCushing’s syndrome and distinguished between pituitaryand ectopic causes with a sensitivity of 82% and a specificityof 79%. In the same patients, the serum cortisol response tothe high-dose dexamethasone suppression test had a slightlyhigher sensitivity (91%) and specificity (80%). However, thecombined criteria of a more than 30% suppression of serum cortisolduring the low-dose dexamethasone suppression test and/or amore than 20% increase in the CRH test had a significantly highersensitivity (97%) and specificity (94%) than either the high-dosedexamethasone or the CRH tests alone in the differential diagnosisof ACTH-dependent Cushing’s syndrome. It produced equivalentinformation to that when high-dose and CRH test results werecombined. We therefore conclude that in our patient series,the serum cortisol response during the low-dose dexamethasonesuppression test is highly sensitive in diagnosing Cushing’ssyndrome and, combined with the results of the serum cortisolresponse to the CRH test, offered a safe and cost-effectivetest in the differential diagnosis of ACTH-dependent Cushing’ssyndrome. There does not appear to be any necessity for retainingthe high-dose dexamethasone suppression test in this diagnosticwork-up.
Present address for A.M.I.: Cattedra di Andrologia, Dipartimentodi Fisiopatologia Medica, Univerisità "La Sapienza" diRoma, Rome 00161, Italy.
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A. M. Isidori, J. P. Monson, G. M. Besser, and A. B. Grossman Authors' Response: Discriminatory Value of Low-Dose Dexamethasone Suppression Test in Establishing the Diagnosis and Differential Diagnosis of Cushing's Syndrome
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M. Zarkovic, J. Ciric, B. Beleslin, and Z. Penezic Discriminatory Value of Low-Dose Dexamethasone Suppression Test in Establishing the Diagnosis and Differential Diagnosis of Cushing's Syndrome
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G. A. Kaltsas, A. M. Isidori, J. P. Monson, G. M. Besser, and A. B. Grossman Authors' Response: The Value of the Low-Dose Dexamethasone Suppression Test in the Differential Diagnosis of Hyperandrogenism in Women
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