Laube Norbert, Zimmermann Diana J
Division of Experimental Urology, Department of Urology, University of Bonn, Bonn, Germany.
Clin Chem Lab Med. 2004;42(6):665-9. doi: 10.1515/CCLM.2004.113.
This study was performed to quantify the effect of a 1-week freezer storage of urine on its calcium oxalate crystallization risk. Calcium oxalate is the most common urinary stone material observed in urolithiasis patients in western and affluent countries. The BONN-Risk-Index of calcium oxalate crystallization risk in human urine is determined from a crystallization experiment performed on untreated native urine samples. We tested the influence of a 1-week freezing on the BONN-Risk-Index value as well as the effect of the sample freezing on the urinary osmolality. In vitro crystallization experiments in 49 native urine samples from stone-forming and non-stone forming individuals were performed in order to determine their calcium oxalate crystallization risk according to the BONN-Risk-Index approach. Comparison of the results derived from original sample investigations with those obtained from the thawed aliquots by statistical evaluation shows that i) no significant deviation from linearity between both results exists and ii) both results are identical by statistical means. This is valid for both, the BONN-Risk-Index and the osmolality data. The differences in the BONN-Risk-Index results of both procedures of BONN-Risk-Index determination, however, exceed the clinically acceptable difference. Thus, determination of the urinary calcium oxalate crystallization risk from thawed urine samples cannot be recommended.
本研究旨在量化尿液冷冻保存1周对草酸钙结晶风险的影响。草酸钙是西方和富裕国家尿路结石患者中最常见的尿结石成分。人体尿液中草酸钙结晶风险的波恩风险指数是通过对未经处理的天然尿液样本进行结晶实验来确定的。我们测试了冷冻1周对波恩风险指数值的影响以及样本冷冻对尿渗透压的影响。为了根据波恩风险指数方法确定49份来自结石形成者和非结石形成者的天然尿液样本的草酸钙结晶风险，进行了体外结晶实验。通过统计评估将原始样本研究结果与解冻后的等分样本结果进行比较，结果表明：i）两者结果之间不存在显著的线性偏差；ii）通过统计学方法，两者结果相同。这对于波恩风险指数和渗透压数据均适用。然而，两种波恩风险指数测定方法的波恩风险指数结果差异超过了临床可接受的差异。因此，不建议从解冻后的尿液样本中测定尿草酸钙结晶风险。
