Department of Nuclear Medicine, Aalborg Hospital, Aarhus University Hospital, Aalborg, Denmark.
Scand J Clin Lab Invest. 2010 Feb;70(1):54-9. doi: 10.3109/00365510903556308.
Previously, data on both the within-subject (SD(I)) and the between-subject (SD(G)) variation of cystatin C in children has not been reported. Thus, this study aimed to determine this biological variation including analytical variation (SD(A)) of both cystatin C and creatinine to characterize the two analytes as renal function markers in children.
On two consecutive days blood samples for duplicate analysis of cystatin C (nephelometric, Dade Behring) and creatinine (enzymatic, Roche) were obtained from 30 children (11 females and 19 males, mean age 8.3 range 2-13 years) referred for GFR measurements by (51)Cr-EDTA clearance. For determination of the between-subject variation only children with normal GFR (n=21) were included. Data were adjusted for the well known age-related increase in creatinine.
The results are given as coefficients of variation. The within-subject variations were identical for both analytes (6.4%). The between-subject variation was 11.1% for cystatin C and 28.4% for creatinine, though decreasing to 20.1% after adjusting for age. The analytical variation was 1.7% and 2.5% for cystatin C and creatinine, respectively. The index of individuality (IOI = SD(I)/SD(G)) was 0.65 for cystatin C and 0.25 for creatinine, though increasing to 0.36 after age-adjustment.
The within-subject variation was identical and low for cystatin C and creatinine suggesting that the two are equally suitable for serial monitoring of renal function in children. Based on the low IOI neither analyte, however, seems suitable as a screening marker of renal function in a healthy population of children using population-based reference intervals.
此前，关于胱抑素 C 在儿童中的个体内（SD(I))）和个体间（SD(G)))）变异性的数据尚未报道。因此，本研究旨在确定胱抑素 C 和肌酐的这种生物变异性，包括分析变异（SD(A)))，以将这两种分析物特征化为儿童肾功能标志物。
连续两天从 30 名儿童（11 名女性和 19 名男性，平均年龄 8.3 岁，范围 2-13 岁）中采集两份血样，用于胱抑素 C（散射比浊法，Dade Behring）和肌酐（酶法，罗氏）的重复分析。为了确定个体间变异，仅纳入肾小球滤过率（GFR）正常的儿童（n=21）。数据经过调整，以考虑肌酐随年龄相关的增加。
结果以变异系数表示。两种分析物的个体内变异性相同（6.4%）。胱抑素 C 的个体间变异性为 11.1%，肌酐为 28.4%，但在调整年龄后降至 20.1%。胱抑素 C 和肌酐的分析变异分别为 1.7%和 2.5%。个体指数（IOI=SD(I)/SD(G))胱抑素 C 为 0.65，肌酐为 0.25，但在年龄调整后增加至 0.36。
胱抑素 C 和肌酐的个体内变异性相同且较低，表明这两种物质在儿童肾功能的连续监测中同样适用。基于较低的 IOI，在使用基于人群的参考区间的健康儿童人群中，这两种分析物都不适合作为肾功能的筛查标志物。
