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Query: UMLS:C0451641 (urolithiasis)
 3,973 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Urinary oxalate is one of the most important constituents of urolithiasis, but the determination of oxalate in urine has not been performed as a routine laboratory examination. We tried to measure oxalate in urine by the enzymatic method with oxalate oxidase. The linearity of the standard curve and reproducibility of this method were confirmed. (Linearity: r = 0.996, S.D./mean: 0.5-3.6%, recovery rate: 99.5 +/- 3.3 (mean +/- S.D.)%) The correlation between this method and gas-chromatographic method was 0.926. The enzymatic method with oxalate oxidase can be utilized for determining the urinary oxalate as a routine laboratory examination.
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PMID:[The determination of oxalate in urine by enzymatic method using oxalate oxidase: comparison between enzymatic and gas-chromatographic methods]. 338 88

To determine reference values, we studied urinary excretion of oxalate prospectively and longitudinally in a cohort of 23 very-low-birth-weight (VLBW) infants. The urinary oxalate concentrations were evaluated in 24-hour urine samples by the oxalate oxidase method. Urine samples were obtained at 1, 2-3, 4-5 and 6-7 weeks of age. The median oxalate amount was 24 mumol/kg body weight/day with a 10th-90th percentile range of 16-45 in the 1st week. Oxalate excretion was highest in 2- to 3-week-old infants (median: 35; percentile range: 26-56 mumol/kg body weight/day). In the 4th-5th week, the median was 24 (percentile range: 15-47) mumol/kg body weight/day and in weeks 6-7 also 24 (percentile range: 10-36) mumol/ kg body weight/day. Also, the urinary oxalate concentration as well as the oxalate-creatinine ratio showed increased values in the first 3 weeks of life and decreased values afterwards. In a multivariate analysis, nutrition or gestational age did not affect the urinary oxalate concentration, the daily amount excreted or the oxalate-creatinine ratio. The investigated parameters (oxalate amount and oxalate-creatinine ratio in urine) were significantly age dependent). The data show that urinary oxalate excretion in VLBW infants approaches levels that are in the same range as those of patients with urolithiasis. Thus the risk of nephrocalcinosis in VLBW infants may be increased.
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PMID:Oxalate excretion during the first 7 weeks in very-low-birth-weight infants. 916 48

Measurement of oxalate in the blood is essential for monitoring primary hyperoxaluria patients with progressive renal impairment and on dialysis prior to transplantation. As no external quality assurance scheme is available for this analyte, we conducted a sample exchange scheme between six laboratories specifically involved with the investigation of primary hyperoxaluria to compare results. The methodologies compared were gas chromatography/mass spectrometry (GCMS), ion chromatography with mass spectrometry (ICMS), and enzymatic methods using oxalate oxidase and spectrophotometry. Although individual laboratories performed well in terms of reproducibility and linearity, there was poor agreement (absolute values) between centres as illustrated by a longer-term comparison of patient results from two of the participating laboratories. This situation was only partly related to differences in calibration and mainly reflected the lower recoveries seen with the ultrafiltration of samples. These findings lead us to conclude that longitudinal monitoring of primary hyperoxaluria patients with deteriorating kidney function should be performed by a single consistent laboratory and the methodology used should always be defined. In addition, plasma oxalate concentrations reported in registry studies and those associated with the risk of systemic oxalosis in published studies need to be interpreted in light of the methodology used. A reference method and external quality assurance scheme for plasma oxalate analysis would be beneficial.
Urolithiasis 2020 Dec
PMID:Plasma oxalate: comparison of methodologies. 3296 Jul 14