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Screening Tests for Cushing's Syndrome: Urinary Free Cortisol Role Measured by LC-MS/MS

2015; Oxford University Press; Volume: 100; Issue: 10 Linguagem: Inglês

10.1210/jc.2015-2507

1945-7197

Filippo Ceccato, Mattia Barbot, Marialuisa Zilio, Anna Chiara Frigo, Nora Albiger, Valentina Camozzi, Giorgia Antonelli, Mario Plebani, Franco Mantero, Marco Boscaro, Carla Scaroni,

Growth Hormone and Insulin-like Growth Factors

As initial screening for Cushing's syndrome (CS), The Endocrine Society guidelines recommend one of the following: the 1-mg dexamethasone suppression test (DST) or late-night salivary cortisol (LNSC) or urinary free cortisol (UFC) measurement. We examined the diagnostic performance of the above-mentioned tests in a series of patients.We retrospectively analyzed 137 patients with clinical conditions suggestive of hypercortisolism: 38 with confirmed CS diagnosis and 99 without (termed non-CS). UFC was measured by liquid chromatography tandem-mass spectrometry, whereas LNSC by the radioimmunometric method and serum cortisol were measured by a chemiluminescence immunoassay.Comparing CS vs non-CS, a cutoff of 138 nmol/L after 1-mg DST revealed the best specificity (SP; 97%), whereas the 50-nmol/L cutoff confirmed the best sensitivity (SE; 100%); the SE and SP for LNSC greater than 14.46 nmol/L were, respectively, 84% and 89%, whereas the SE and SP for UFC greater than 170 nmol per 24 hours, they were 97% and 91%. Overall, UFC revealed both a combined higher positive and a lower negative likelihood ratio among first-line tests (respectively 10.7 and 0.03). Computing a receiver-operating curve -contrast analysis to compare the power of each single test with that of the others, alone or combined (DST+LNSC, DST+UFC, and LNSC+UFC) or with that of all the tests together (DST+LNSC+UFC), the UFC assay was at least as good as all the other possible combinations.Measuring UFC by liquid chromatography tandem-mass spectrometry achieves the best accuracy in diagnosing CS among patients presenting with suspected hypercortisolism.