Department of Internal Medicine, Seoul National University College of Medicine, Seoul, Korea.
Clin Exp Rheumatol. 2013 Jul-Aug;31(4):584-8. Epub 2013 May 27.
The accurate assessment of proteinuria is critical for the management of lupus nephritis. Measuring the protein to creatinine (P/C) ratio in random spot urine (RSU) samples has been introduced as an alternative to the 24-hour (24h) urine collection method. However, it remains unclear as to whether the RSU P/C ratio is reliable for assessing lupus nephritis (LN) in routine clinical practice.
In total, 275 pairs of 24h urine and RSU samples from 102 patients with biopsy-proven LN were analysed. The correlation and concordance between the P/C ratios in the two sample types were assessed by Pearson or Spearman correlation and intra-class correlation coefficient (ICC) using mixed models for repeated measurements, respectively.
The mean 24h urine P/C ratio was 3.2 ± 4.9. Overall, RSU P/C ratio correlated strongly with the 24h urine P/C ratio (r=0.944, p<0.001) with an excellent agreement (ICC=0.949, 95% confidence interval [CI]: 0.69-1.00). Subgroup analyses revealed that the correlation remained high in class II, III, IV, and V LN (rho=0.868, p<0.001; rho=0.649, p=0.007; r=0.945, p<0.001; and rho=0.900, p=0.001, respectively). The correlation between the 24h urine and RSU P/C ratio in the range of 0.5 to 3 was good (r=0.720, p<0.001) with ICC of 0.659 (95%CI 0.554-0.812). RSU P/C ratio ≥0.5 could predict 24h PCR ≥0.5 with 91.7% sensitivity and 70.2% specificity, whereas RSU P/C ratio ≥1.0 increased specificity up to 94.7%.
The RSU P/C ratio is an excellent alternative to the 24 hour P/C ratio for assessing the presence of clinically significant proteinuria in LN. RSU P/C ratio >1.0 may prompt directly to a renal biopsy, whereas RSU P/C ratio between 0.5-1.0 should be followed by a confirmatory 24h urine collection.
蛋白尿的准确评估对狼疮肾炎的治疗至关重要。随机尿样（RSU）中蛋白与肌酐（P/C）比值的测量已被作为 24 小时尿液收集方法的替代方法。然而，RSU P/C 比值在常规临床实践中是否可用于评估狼疮肾炎（LN）尚不清楚。
共分析了 102 例经活检证实的 LN 患者的 275 对 24 小时尿液和 RSU 样本。使用混合重复测量模型，分别通过 Pearson 或 Spearman 相关分析和组内相关系数（ICC）评估两种样本类型的 P/C 比值之间的相关性和一致性。
24 小时尿 P/C 比值的平均值为 3.2±4.9。总体而言，RSU P/C 比值与 24 小时尿 P/C 比值高度相关（r=0.944，p<0.001），一致性极好（ICC=0.949，95%置信区间[CI]：0.69-1.00）。亚组分析显示，在 LN II、III、IV 和 V 类中，相关性仍然很高（rho=0.868，p<0.001；rho=0.649，p=0.007；r=0.945，p<0.001；rho=0.900，p=0.001）。24 小时尿和 RSU P/C 比值在 0.5 至 3 范围内的相关性较好（r=0.720，p<0.001），ICC 为 0.659（95%CI 0.554-0.812）。RSU P/C 比值≥0.5 可预测 24 小时 PCR≥0.5，灵敏度为 91.7%，特异性为 70.2%，而 RSU P/C 比值≥1.0 可使特异性提高至 94.7%。
RSU P/C 比值是评估 LN 中临床显著蛋白尿的 24 小时 P/C 比值的极好替代方法。RSU P/C 比值>1.0 可能提示直接进行肾活检，而 RSU P/C 比值在 0.5-1.0 之间时，应随后进行确认性 24 小时尿液收集。
