BACKGROUND Urine albumin-to-creatinine ratio (ACR) and protein-to-creatinine ratio (PCR) are used to measure urine protein. Recent guidelines endorse ACR use, and equations have been developed incorporating ACR to predict risk of kidney failure. For situations in which PCR only is available, having a method to estimate ACR from PCR as accurately as possible would be useful. METHODS We used data from a population-based cohort of 47,714 adults in Alberta, Canada, who had simultaneous assessments of urine ACR and PCR. After log-transforming ACR and PCR, we used cubic splines and quantile regression to estimate the median ACR from a PCR, allowing for modification by specified covariates. On the basis of the cubic splines, we created models using linear splines to develop equations to estimate ACR from PCR. In a subcohort with eGFR<60 ml/min per 1.73 m2, we then used the kidney failure risk equation to compare kidney failure risk using measured ACR as well as estimated ACR that had been derived from PCR. RESULTS We found a nonlinear association between log(ACR) and log(PCR), with the implied albumin-to-protein ratio increasing from <30% in normal to mild proteinuria to about 70% in severe proteinuria, and with wider prediction intervals at lower levels. Sex was the most important modifier of the relationship between ACR and PCR, with men generally having a higher albumin-to-protein ratio. Estimates of kidney failure risk were similar using measured ACR and ACR estimated from PCR. CONCLUSIONS We developed equations to estimate the median ACR from a PCR, optionally including specified covariates. These equations may prove useful in certain retrospective clinical or research applications where only PCR is available.

中文翻译：

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从蛋白质与肌酐比率估计尿白蛋白与肌酐比率：使用当天测量建立方程。


背景技术尿白蛋白与肌酐比值(ACR)和蛋白与肌酐比值(PCR)用于测量尿蛋白。最近的指南支持 ACR 的使用，并且已经开发出结合 ACR 的方程来预测肾衰竭的风险。对于仅可使用 PCR 的情况，拥有一种尽可能准确地根据 PCR 估计 ACR 的方法将很有用。方法 我们使用了加拿大艾伯塔省 47,714 名成年人的人群数据，他们同时对尿液 ACR 和 PCR 进行了评估。对 ACR 和 PCR 进行对数转换后，我们使用三次样条和分位数回归来估计 PCR 的中值 ACR，从而允许通过指定的协变量进行修改。在三次样条的基础上，我们使用线性样条创建了模型，以开发方程来估计 PCR 的 ACR。在 eGFR<60 ml/min/1.73 m2 的亚队列中，我们使用肾衰竭风险方程，使用测量的 ACR 以及从 PCR 得出的估计 ACR 来比较肾衰竭风险。结果我们发现 log(ACR) 和 log(PCR) 之间存在非线性关联，隐含的白蛋白与蛋白质比率从正常至轻度蛋白尿的 <30% 增加到严重蛋白尿的约 70%，并且预测区间更宽较低的水平。性别是 ACR 和 PCR 之间关系的最重要调节因素，男性通常具有较高的白蛋白与蛋白质比率。使用测量的 ACR 和通过 PCR 估计的 ACR 对肾衰竭风险的估计相似。结论 我们开发了方程来估计 PCR 的中值 ACR，可选地包括指定的协变量。这些方程可能在某些仅可使用 PCR 的回顾性临床或研究应用中有用。