Measurement Error as Alternative Explanation for the Observation that CrCl/GFR Ratio is Higher at Lower GFR
Measurement Error as Alternative Explanation for the Observation that CrCl/GFR Ratio is Higher at Lower GFR
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DOI：
10.2215/cjn.12821215
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发表时间：
2016-09-01
影响因子：
9.8
通讯作者：
Hsu, Chi-yuan
中科院分区：
文献类型：
--
作者：
Zhang, Xuehan;McCulloch, Charles E.;Hsu, Chi-yuan
背景和目的在较低的GFR水平下，通过尿肌酐清除率（CrCl）高估GFR长期以来被认为是由于肌酐分泌增加。然而，这并没有考虑到由于短期的生物变异性或测试imprecision.Design，设置，参与者，和measurements测量GFR（和CrCl）的误差的贡献我们分析了1342名参与者的横断面数据从慢性肾功能不全队列研究与基线测量GFR的碘酞清除率（iGFR）和CrCl的24小时尿液收集。我们研究了CrCl/iGFR的比率分类的iGFR的类别，也由CrCl.Results总体类别，平均CrCl/iGFR的比率为1.13。在较低的iGFR类别中，CrCl/iGFR比值较高。相比之下，该比率在较低CrCl水平下较低。我们假设这些关系可能是由于测量误差，这是通过在模拟和建模练习中复制这些趋势得到支持的，在模拟和建模练习中，CrCl/iGFR的比值与真实肾功能没有变化，但考虑了CrCl和iGFR测量误差的影响（文献中先前描述的幅度）。在我们的模拟数据中，当按观察到的iGFR类别对患者进行分类时，观察到的CrCl/iGFR比值在较低的观察到的iGFR水平下较高。当相同的患者进行分类的观察CrCl的类别，观察到的CrCl/iGFR的比率是较低的观察CrCl levels.Conclusions相结合的经验和建模结果表明，测量误差（在CrCl和iGFR）应被视为一种替代解释的长期观察，CrCl的比率iGFR变大，iGFR降低。
Background and objectives Overestimation of GFR by urinary creatinine clearance (CrCl) at lower levels of GFR has long been attributed to enhanced creatinine secretion. However, this does not take into consideration the contribution of errors in measured GFR (and CrCl) due to short-term biologic variability or test imprecision.Design, setting, participants, & measurements We analyzed cross-sectional data among 1342 participants from the Chronic Renal Insufficiency Cohort study with baseline measurement of GFR by iothalamate clearance (iGFR) and CrCl by 24-hour urine collection. We examined the CrCl/iGFR ratio classified by categories of iGFR and also by categories of CrCl.Results Overall, mean CrCl/iGFR ratio was 1.13. CrCl/iGFR ratio was higher at lower iGFR categories. In contrast, this ratio was lower at lower CrCl levels. We hypothesize these relationships could be due to measurement error, which is bolstered by replicating these trends in a simulation and modeling exercise in which there was no variation in the ratio of CrCl/iGFR with true kidney function but taking into account the effect of measurement error in both CrCl and iGFR (of magnitudes previously described in the literature). In our simulated data, the observed CrCl/iGFR ratio was higher at lower observed iGFR levels when patients were classified by categories of observed iGFR. When the same patients were classified by categories of observed CrCl, the observed CrCl/iGFR ratio was lower at lower observed CrCl levels.Conclusions The combined empirical and modeling results suggest that measurement errors (in both CrCl and iGFR) should be considered as an alternative explanation for the longstanding observation that the ratio of CrCl to iGFR gets larger as iGFR decreases.