Performance of LC–MS/MS and immunoassay based 24-h urine free cortisol in the diagnosis of Cushing's syndrome

We examined 24-h urine samples from patients with surgically confirmed CS (n = 77; Cushing’s disease (n = 44), ectopic CS (n = 5), adrenal CS (n = 28)) and patients in whom Cushing’s syndrome was excluded (n = 97) by long-term follow up. UFC was first measured by automated chemiluminescence immunoassays (ADVIA Centaur, Siemens; LIAISON, DiaSorin). Aliquots of all samples were also analyzed by liquid chromatography-tandem mass spectrometry (LC–MS/MS). Statistics: Passing-Bablok Regression, Receiver operating characteristic (ROC) analysis with Youden’s index calculation. UFC of CS patients were higher with both immunoassays compared to LC–MS/MS (913 +/- 235 vs. 303 +/- 155 μg/24 h (ADVIA) and 898 +/-216 vs. 399 +/- 196 μg/24 h (LIAISON)). Similarly, UFC were higher with immunoassays than with LC–MS/MS in the control group (223 +/- 10 vs. 23 +/- 2 μg/24 h (ADVIA) and 105 +/- 6 vs. 27 +/- 4 ug/24 h for (LIAISON)). Passing-Bablok regression showed good correlation between LC–MS/MS and ADVIA as well as between LCMS/MS and LIAISON (r = 0.96 and r = 0.99, p < 000.1) but less correlation in controls (r = 0.83 and r = 0.74, respectively, p < 000.1). ROC calculation revealed the highest ROC AUC (0.89) for the LIAISON immunoassay, followed by LC–MS/MS (0.82) and the ADVIA (0.80). In direct comparison, AUCs from LC–MS/MS and immunoassays in the same patient were not statistically different (p < ...
Source: The Journal of Steroid Biochemistry and Molecular Biology - Category: Biochemistry Source Type: research