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Improvement and Validation of d-Xylose Determination in Urine and Serum as a New Tool for the Noninvasive Evaluation of Lactase Activity in Humans

AuthorsHermida, Carmen; Martínez-Costa, Oscar H. ; Corrales, Guillermo ; Sánchez, Valentina; Codoceo, Rosa; Fernández-Mayoralas, Alfonso ; Aragón, Juan J.
Intestinal lactase
Analytical validation
Issue Date2014
PublisherJohn Wiley & Sons
CitationJournal of Clinical Laboratory Analysis 28(6): 478-486 (2014)
Abstract[Background]: The phloroglucinol assay is the current method for d-xylose determination in urine/plasma/serum. However, its sensitivity is limited when low amounts of d-xylose are to be measured, such as in the noninvasive evaluation of intestinal lactase with 4-galactosylxylose (gaxilose). An improved assay was therefore needed. [Methods]: We developed and validated a modified version of the phloroglucinol-based assay for quantification of d-xylose in urine/serum samples. A method for gaxilose determination by gas chromatography (GC) was also optimized. [Results]: Linearity ranged from 0.125 to 5.0 mg/l (5¿200 mg/l in original sample). Accuracy at LOQ (0.125 mg/l) was 0.97/2.49% in spiked urine/serum; for other quality controls (QC), it was <1.27%. Intra- and interassay precision at LOQ were 6.02% and 6.45% for urine, and 8.86% and 10.00%, respectively, for serum; for other QC, precision was <2.15%. Linearity of gaxilose determination by GC was 3.90¿195.17 for urine and 9.75-195.17 mg/l for serum with acceptable sensitivity and reproducibility. The method proved adequate for the d-xylose determination in healthy and hypolactasic subjects after oral administration of gaxilose. [Conclusions]: The modified method provides high sensitivity and robustness for d-xylose quantification in urine/serum for routine clinical use especially in the noninvasive diagnosis of intestinal lactase deficiency with the gaxilose test.
Descriptionet al.
Identifiersdoi: 10.1002/jcla.21713
issn: 0887-8013
e-issn: 1098-2825
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