Professor Edgard Santos Hospital University, Federal University of Bahia, Rua Doutor Augusto Viana - Canela, Salvador, BA, 40110-060, Brazil.
Master and Doctoral Graduate Program in Medicine and Health, Federal University of Bahia, Rua Doutor Augusto Viana - Canela, Salvador, BA, 40110-060, Brazil.
BMC Nephrol. 2024 Nov 21;25(1):418. doi: 10.1186/s12882-024-03804-7.
The 24-h urine protein (24-hUP) excretion is the gold standard for evaluating proteinuria. This study aimed to evaluate the diagnostic efficacy of protein/creatinine ratio (PCR) for estimating 24-hUP at various levels of renal function and proteinuria levels.
A cross-sectional study was conducted between December 2021 and December 2023 in Salvador, Bahia-Brazil, as an extension of previously published data from the TUNARI study. The study included 217 samples from 152 patients with various levels of renal function and proteinuria. PCR in isolated samples and 24-hUP were determined conventionally within a 24-h timeframe. Patients were classified into three groups according to the level of renal function (Group 1 = 10 to < 30 mL/min, Group 2 = 30-60 mL/min, and Group 3 = > 60 mL/min) and level of proteinuria (< 0.3 g/day, 0.3-3.5 g/day, and > 3.5 g/day). The data were analyzed using the Spearman correlation (r), coefficient of determination (r), Bland-Altman plots and receiver operating characteristic (ROC) curve. Likelihood ratios, positive (LR +), and negative (LR-) were derived from the sensitivity and specificity of PCR.
Mean age was 41.5 ± 15.7 years, 61.8% were women, 36.8% Black and 52% Mixed-race. Glomerulopathies constituted 80.3%; 46.1% with lupus nephritis. Of the total urine samples, we observed a high correlation between PCR in the total sample of 24-hUP sample (r = 0.86, p < 0.001) across different levels of renal function. However, agreement between PCR and 24-hUP was reduced at higher levels of proteinuria. The ROC analysis showed an AUC of 0.95 (95% CI = 0.92, 0.98), sensitivity of 91% and specificity of 86.5% (LR + 6.7; LR- 0.1), with an optimal cut-off of 0.77. These results were similar across renal function levels. Proteinuria ≤ 0.3 g/day showed a high sensitivity of 83.3% and specificity of 90%, with an area under (AUC) of 0.85 (95% CI = 0.71; 0.94). In the 24-hUP range > 0.3-3.5 g/day, the sensitivity was 64.1%, the specificity was 84.6%, and the AUC was 0.76 (95% CI = 0.67; 0.84), PCR detected all cases > 3.5 g/day.
PCR is a suitable measure to be used as an indicator of 24-hUP at different levels of renal function, but may have limitations at higher levels of proteinuria. Analysis of PCR by proteinuria level found that agreement as well as sensitivity decreases at higher levels, but it maintains good specificity and is able to identify nephrotic range proteinuria.
24 小时尿蛋白（24-hUP）排泄是评估蛋白尿的金标准。本研究旨在评估蛋白/肌酐比值（PCR）在不同肾功能和蛋白尿水平下估计 24-hUP 的诊断效能。
这是一项在 2021 年 12 月至 2023 年 12 月期间在巴西巴伊亚州萨尔瓦多进行的横断面研究，是之前发表的 TUNARI 研究数据的扩展。该研究包括了来自 152 名不同肾功能和蛋白尿水平的患者的 217 个样本。PCR 在分离样本和 24-hUP 都在 24 小时内常规测定。根据肾功能水平（第 1 组：10 至<30ml/min；第 2 组：30-60ml/min；第 3 组：>60ml/min）和蛋白尿水平（<0.3g/天、0.3-3.5g/天和>3.5g/天）将患者分为三组。数据使用 Spearman 相关系数（r）、决定系数（r²）、Bland-Altman 图和受试者工作特征（ROC）曲线进行分析。来自 PCR 的敏感性和特异性得出似然比（LR+和 LR-）。
平均年龄为 41.5±15.7 岁，61.8%为女性，36.8%为黑人，52%为混血儿。肾小球疾病占 80.3%；其中 46.1%为狼疮性肾炎。在所有尿液样本中，我们观察到 PCR 与 24-hUP 样本的总样本之间存在高度相关性（r=0.86，p<0.001），跨越不同的肾功能水平。然而，在较高水平的蛋白尿时，PCR 与 24-hUP 的一致性降低。ROC 分析显示 AUC 为 0.95（95%CI=0.92，0.98），敏感性为 91%，特异性为 86.5%（LR+=6.7；LR-=0.1），最佳截断值为 0.77。这些结果在不同肾功能水平下相似。蛋白尿≤0.3g/天的敏感性为 83.3%，特异性为 90%，AUC 为 0.85（95%CI=0.71；0.94）。在 24-hUP 范围为 0.3-3.5g/天的范围内，敏感性为 64.1%，特异性为 84.6%，AUC 为 0.76（95%CI=0.67；0.84），PCR 检测到所有>3.5g/天的病例。
PCR 是一种适用于不同肾功能水平 24-hUP 的指标，但在较高水平的蛋白尿时可能存在局限性。根据蛋白尿水平分析 PCR 发现，随着水平的升高，一致性和敏感性降低，但仍具有良好的特异性，能够识别肾病范围的蛋白尿。
