Andersson Lena, Haraldsson Börje, Johansson Caroline, Barregard Lars
Department of Occupational and Environmental Medicine, Sahlgrenska University Hospital and Academy, PO Box 414, S-405 30 Göteborg, Sweden.
Nephrol Dial Transplant. 2008 Apr;23(4):1252-6. doi: 10.1093/ndt/gfm729. Epub 2007 Nov 6.
Alpha-1-microglobulin (A1M) is a low molecular weight protein that can be measured in urine and used as a marker for tubular function, assuming that the normal variability within and between individuals is known. The aims of this study were to investigate this variability, to find the optimal way of sampling and quantifying A1M in spot urine samples to reflect the 24 h excretion and to examine storage stability. Method. Timed urine specimens were collected from 29 healthy volunteers at fixed time points over 24 h on two separate days. Volumes, creatinine and specific gravity were determined. All samples were analysed with a commercial ELISA for A1M.
We found a clear diurnal variation in A1M excretion rate and a gender effect (higher in males). The excretion rate was higher in the daytime, with high urinary flow, compared to overnight values. A1M excretion in spot urine samples was highly correlated with the 24 h excretion at all times except 22:00 in male subjects. Urinary A1M adjusted for creatinine concentration correlated well with the 24 h excretion. Variability within individuals was only 20% of the total variability in 24 h A1M excretion, but 43% in first morning urine. Expressed as CV, the intra-individual variability (between days) was 29% in 24 h excretion.
We conclude that diurnal variation and gender should be taken into account when comparing groups. Moreover, in spot samples (e.g. first morning samples) adjustment of A1M for creatinine or specific gravity is a reliable alternative to 24 h urine.
α1-微球蛋白（A1M）是一种低分子量蛋白质，若已知个体内及个体间的正常变异性，可在尿液中检测并用作肾小管功能的标志物。本研究的目的是调查这种变异性，找到采集和定量即时尿样中A1M的最佳方法以反映24小时排泄量，并检测储存稳定性。方法：在两天的24小时内，于固定时间点从29名健康志愿者收集定时尿样。测定尿量、肌酐和比重。所有样本均采用商用ELISA法分析A1M。
我们发现A1M排泄率存在明显的昼夜变化以及性别效应（男性较高）。与夜间值相比，白天尿量高时排泄率更高。除男性受试者22:00外，即时尿样中A1M排泄量与24小时排泄量在所有时间均高度相关。经肌酐浓度校正的尿A1M与24小时排泄量相关性良好。个体内变异性仅占24小时A1M排泄总量变异性的20%，但在晨尿中占43%。以CV表示，个体内（不同天之间）变异性在24小时排泄量中为29%。
我们得出结论，在比较不同组时应考虑昼夜变化和性别。此外，在即时样本（如晨尿样本）中，对A1M进行肌酐或比重校正可作为24小时尿液检测的可靠替代方法。
