Department of Medical Biochemistry, Oslo University Hospital Rikshospitalet, Norway.
Scand J Clin Lab Invest. 2010 Apr 19;70(3):145-50. doi: 10.3109/00365510903578765.
For assessment of total oxalic acid (OX) status, reliable quantification of OX in both urine and plasma is important. For urine, but not plasma, a commercial kit is available. We have recently described a LC-MSMS method for OX in plasma. The aim of the present study was to evaluate the usefulness of this assay for urine. We also wanted to evaluate if 24 h urine collection could be substituted by OX/creatinine-ratio (U-OX/crea) in spot-urine, and establish precursory reference intervals for U-OX/crea in children and adults.
Acidified urines were analysed and relevant validation parameters assessed. Diurnal excretion patterns were investigated in nine healthy volunteers on self-chosen diets. For method comparison, 29 urine samples were analysed with both the present method and a commercial urine-oxalate kit. Precursory reference values for U-OX/crea in children and adults (N=103, 1 month-76 years) were calculated.
The within-batch coefficient of variation (CV) was 2.5% and a relative recovery of 97% in urine spiked with 5-200 micromol/L OX was found. The LC-MSMS method gave 7.9% higher OX values compared to the kit. No significant diurnal pattern of U-OX/crea was observed. U-OX/crea in children decreases with age, with no gender dependency. In adults no age variation was found, but females had somewhat higher U-OX/Crea compared to males.
The LC-MSMS method has proven useful for urinary OX quantification. Random spot-urine samples can be used. Age-dependent reference limits for U-OX/crea must be applied in children, in contrast to adults.
为了评估总草酸盐（OX）的状态，可靠地定量尿液和血浆中的 OX 非常重要。虽然有用于尿液的商业试剂盒，但血浆的检测方法却没有。我们最近描述了一种用于检测血浆 OX 的 LC-MSMS 方法。本研究的目的是评估该方法在尿液中的应用价值。我们还想评估是否可以用单次尿样的 OX/肌酐比值（U-OX/crea）代替 24 小时尿液收集，并建立儿童和成人 U-OX/crea 的初步参考区间。
对酸化尿液进行分析并评估相关验证参数。在 9 名志愿者自选饮食的情况下，研究了尿液的日间排泄模式。为了进行方法比较，用本方法和商业尿液草酸盐试剂盒分析了 29 个尿液样本。计算了儿童和成人（N=103，1 个月-76 岁）的 U-OX/crea 初步参考值。
批内变异系数（CV）为 2.5%，尿液中 OX 浓度为 5-200 微摩尔/升时，相对回收率为 97%。LC-MSMS 方法检测到的 OX 值比试剂盒高 7.9%。未观察到 U-OX/crea 的明显日间变化模式。儿童的 U-OX/crea 随年龄降低，与性别无关。在成年人中，未发现年龄变化，但女性的 U-OX/Crea 略高于男性。
LC-MSMS 方法已被证明可用于尿液 OX 定量。可以使用随机单次尿样。与成年人不同，儿童必须应用年龄依赖性的 U-OX/crea 参考值。
