Hospital Universitário Professor Edgard Santos, Universidade Federal da Bahia (UFBA), Salvador, Brazil.
Programa de Pós-graduação em Medicina e Saúde (PPgMS), Universidade Federal da Bahia (UFBA), Salvador, Brazil.
Nephron. 2023;147(11):643-649. doi: 10.1159/000531333. Epub 2023 Jun 24.
Lupus nephritis (LN) occurs in approximately 50% of people with systemic lupus erythematosus (SLE). The 24-h proteinuria (gold standard) is measured among other tests for the control and monitoring of LN activity. This study investigates the use of the protein/creatinine ratio (PCR) as an alternative for the detection of proteinuria and its accuracy compared to the gold standard in a predominantly non-white population.
This was a prospective study conducted in Salvador, Brazil, between December 2021 and May 2022. We invited adult patients diagnosed with SLE and LN, regardless of their disease activity. The estimation of the PCR and 24-h proteinuria was performed using conventional methods. The analysis used was Spearman's r correlation coefficient (rs), coefficient of determination (r2), and concordance by the Bland-Altman method. A specific sensitivity was measured by the ROC curve with its respective cut-off by the Youden Index.
We compared 112 samples of 75 patients with LN, with a mean age of 34.5 ± 11.8 years. Of these patients, 85% were women, 87.9% were non-white. A high degree of correlation was observed between PCR with 24-h proteinuria (rs = 0.77 and r2 = 0.59). The ROC analysis shows an area under the curve of 0.92 and the cut-off point calculated by the Youden Index was 0.78 with a sensitivity of 90.0% and specificity of 82%. However, the Bland-Altman graph indicated decreasing concordance as the degree of proteinuria increased, despite showing concordance at high levels of proteinuria.
The PCR shows high sensitivity to follow-up patients with LN when compared with 24-h proteinuria. Our findings suggest that PCR is a useful parameter for the evaluating and monitoring patients in complete remission. However, in cases of partial remission, the utility of PCR is limited.
狼疮肾炎（LN）发生在约 50%的系统性红斑狼疮（SLE）患者中。24 小时蛋白尿（金标准）是 LN 活动控制和监测的其他测试之一。本研究调查了在以非白种人为主的人群中，使用蛋白/肌酐比值（PCR）作为检测蛋白尿的替代方法及其与金标准的准确性。
这是一项在巴西萨尔瓦多进行的前瞻性研究，时间为 2021 年 12 月至 2022 年 5 月。我们邀请了患有 SLE 和 LN 的成年患者，无论其疾病活动如何。PCR 和 24 小时蛋白尿的估计使用常规方法进行。使用 Spearman's r 相关系数（rs）、决定系数（r2）和 Bland-Altman 方法的一致性进行分析。通过受试者工作特征（ROC）曲线测量特定的敏感性，并通过 Youden 指数计算其相应的截止值。
我们比较了 75 例 LN 患者的 112 个样本，患者平均年龄为 34.5±11.8 岁。这些患者中，85%为女性，87.9%为非白种人。PCR 与 24 小时蛋白尿之间存在高度相关性（rs=0.77，r2=0.59）。ROC 分析显示曲线下面积为 0.92，Youden 指数计算的截止值为 0.78，敏感性为 90.0%，特异性为 82%。然而，Bland-Altman 图表明，尽管在高蛋白尿水平下具有一致性，但随着蛋白尿程度的增加，一致性降低。
与 24 小时蛋白尿相比，PCR 对 LN 患者的随访具有较高的敏感性。我们的研究结果表明，PCR 是评估和监测完全缓解患者的有用参数。然而，在部分缓解的情况下，PCR 的应用有限。
