Journal
CLINICAL CHEMISTRY AND LABORATORY MEDICINE
Volume 56, Issue 7, Pages 1109-1116Publisher
WALTER DE GRUYTER GMBH
DOI: 10.1515/cclm-2017-0806
Keywords
analytical process; 24-h urinary free cortisol; interlaboratory agreement; liquid chromatography-tandem mass spectrometry
Categories
Ask authors/readers for more resources
Background: 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. Methods: 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. Results: 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 (<50 or >270 nmol/day), negative or positive bias was noted. Conclusions: 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.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available