Finocchiaro R, D'Eufemia P, Celli M, Zaccagnini M, Viozzi L, Troiani P, Mannarino O, Giardini O
Istituto di Clinica Pediatrica, Università di Roma La Sapienza, Italia.
Urol Res. 1998;26(6):401-5. doi: 10.1007/s002400050076.
We present the results of a cyanide-nitroprusside test (CNT) after a standardized dilution procedure of urine samples and report the efficiency of this method in detecting heterozygotes for cystinuria when applied on an open pediatric population. In the preliminary study we assayed by quantitative determination of amino acids 162 urine samples from a hospital population identifying 24 type III heterozygotes and 2 type II heterozygotes for cystinuria. The classic CNT gave 38 false positive results and 5 false negative results showing a sensitivity and specificity of 0.808 and 0.721, respectively. When progressively diluted, all samples of heterozygotes remained CNT positive up to a creatinine concentration of 90 mg/dl. At this level of dilution 31 out of 38 false positive turned to negative, thus obtaining a specificity of 0.922 without a lowering of the sensitivity in detecting heterozygotes. The standardized dilution at 90 mg/dl of creatinine concentration was applied to 74.7% of a population of 1024 schoolchildren. In this way 163 out of 210 positive results were eliminated and thus the specificity of CNT rose from 0.789 to 0.953. On the basis of these results, the method proposed can be regarded as reliable and useful for a screening program in detecting heterozygotes for cystinuria.
我们展示了对尿液样本进行标准化稀释程序后氰化物-硝普钠试验（CNT）的结果，并报告了该方法应用于开放的儿科人群时检测胱氨酸尿症杂合子的效率。在初步研究中，我们通过定量测定氨基酸对来自医院人群的162份尿液样本进行了分析，确定了24例III型胱氨酸尿症杂合子和2例II型杂合子。经典的CNT产生了38例假阳性结果和5例假阴性结果，敏感性和特异性分别为0.808和0.721。当逐步稀释时，所有杂合子样本在肌酐浓度达到90mg/dl之前一直保持CNT阳性。在这个稀释水平下，38例假阳性中的31例转为阴性，从而在检测杂合子时获得了0.922的特异性且不降低敏感性。将肌酐浓度标准化稀释至90mg/dl应用于1024名学童人群的74.7%。通过这种方式，210例阳性结果中的163例被排除，因此CNT的特异性从0.789提高到0.953。基于这些结果，所提出的方法可被视为在检测胱氨酸尿症杂合子的筛查项目中可靠且有用。
