Leung Y Y, Szeto C C, Tam L S, Lam C W K, Li E K, Wong K C, Yu S W, Kun E W
Department of Medicine and Geriatrics, Tai Po Hospital, 9 Chuen On Road, Taipo, N.T., Hong Kong SAR.
Rheumatology (Oxford). 2007 Apr;46(4):649-52. doi: 10.1093/rheumatology/kel360. Epub 2006 Oct 25.
To evaluate the accuracy of urine protein-to-creatinine (P/C) ratio in an untimed urine specimen as compared with 24 h total protein excretion for measurement of proteinuria in patients with lupus nephritis.
Proteinuria in patients with lupus nephritis was assessed by 24 h total protein excretion and spot urine P/C ratio. Correlation and limits of agreement between the two methods were evaluated. The discriminant cutoff values for spot urine P/C ratio in predicting 24 h protein 'threshold' excretion of > or =0.3, > or =0.5, > or =1.0 and > or =3.5 g/day were determined using receiver operating characteristic curves.
A total of 165 samples were available for assessment with 21.8% excluded due to inadequate collection. A strong correlation (r = 0.91, P < 0.0001) was found between spot urine P/C ratio and 24 h urine protein excretion. Bland-Altman plot showed the two tests had acceptable limits of agreement in low level of protein excretion (-0.86 to +0.92 g/day when protein excretion was <2.0 g/day). The limits became wider as the protein excretion increased. The spot urine P/C ratios of 0.45 (sensitivity 0.92; specificity 0.88), 0.7 (0.92; 0.89) and 1.84 (1.0; 0.86) mg/mg reliably predicted 24 h urine total protein equivalent 'thresholds' at > or =0.5, 1.0 and 3.5 g/day.
This study supports the recommendation of using spot urine P/C ratio in screening and monitoring proteinuria in patients with lupus nephritis. However, in assessing the exact amount of proteinuria, the urine P/C ratio may have unacceptably wide limits of agreement in high protein excretion range.
评估在狼疮性肾炎患者中，与24小时总蛋白排泄量相比，随机尿标本中尿蛋白与肌酐比值（P/C）用于测量蛋白尿的准确性。
通过24小时总蛋白排泄量和随机尿P/C比值评估狼疮性肾炎患者的蛋白尿情况。评估两种方法之间的相关性和一致性界限。使用受试者工作特征曲线确定随机尿P/C比值预测24小时蛋白“阈值”排泄量分别≥0.3、≥0.5、≥1.0和≥3.5克/天的判别临界值。
共有165份样本可供评估，21.8%因收集不充分被排除。随机尿P/C比值与24小时尿蛋白排泄量之间存在强相关性（r = 0.91，P < 0.0001）。Bland-Altman图显示，在低蛋白排泄水平（蛋白排泄量<2.0克/天时为-0.86至+0.92克/天），两种检测方法的一致性界限可接受。随着蛋白排泄量增加，界限变宽。随机尿P/C比值为0.45（敏感性0.92；特异性0.88）、0.7（0.92；0.89）和1.84（1.0；0.86）毫克/毫克时，可可靠预测24小时尿总蛋白当量“阈值”分别≥0.5、1.0和3.5克/天。
本研究支持在狼疮性肾炎患者中使用随机尿P/C比值进行蛋白尿筛查和监测的建议。然而，在评估蛋白尿的确切量时，在高蛋白排泄范围内，尿P/C比值的一致性界限可能宽得无法接受。
