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LC-MSMS assays of urinary cortisol, a comparison between four in-house assays

2018; De Gruyter; Volume: 56; Issue: 7 Linguagem: Inglês

10.1515/cclm-2017-0806

1437-4331

Julie Brossaud, Monique Leban, Jean‐Benoît Corcuff, F Casson, Anne-Gaëlle Leloupp, Damien Masson, Valérie Moal, Kalyane Bach‐Ngohou,

Hormonal Regulation and Hypertension

Twenty-four hour urinary free cortisol (UFC) determination can be used for screening and follow-up of Cushing syndrome (CS). As immunoassay methods lack specificity for UFC measurement, the use of high-performance liquid chromatography coupled to mass spectrometer (LC-MSMS) is recommended. The aim of our study was to compare UFC results using four LC-MSMS methods performed in four independent laboratories in order to evaluate interlaboratory agreement.Frozen aliquots of 24-h urine samples (78 healthy volunteers and 20 patients with CS) were sent to four different laboratories for analysis. Following liquid-liquid or solid-liquid extraction, UFC were determined using four different LC-MSMS assay.UFC intra- and interassays variation coefficients were lower than 10% for each centre. External quality control results were not significantly different. UFC normal ranges (established from healthy volunteers) were 17-126, 15-134, 12-118 and 27-157 nmol/day, respectively. Classification of UFC from healthy volunteers and patients with CS using a 95th percentile threshold was similar. However, for extreme UFC values ( 270 nmol/day), negative or positive bias was noted.Even for highly specific methods such as LC-MSMS, variations of results can be found depending on analytical process. Validation of LC-MSMS methods including determination of the reference range is essential.