Welch Center for Prevention, Epidemiology, and Clinical Research, Johns Hopkins University, Baltimore, MD.
Am J Kidney Dis. 2010 Jul;56(1):39-49. doi: 10.1053/j.ajkd.2010.02.347.
Evaluating the accuracy of estimated glomerular filtration rate (eGFR) derived from serum creatinine (SCr) and serum cystatin C (SCysC) equations requires gold-standard measures of GFR. However, the influence of imprecise measured GFRs (mGFRs) on estimates of equation error is unknown.
Diagnostic test study.
SETTING & PARTICIPANTS: 1,995 participants from the Modification of Diet in Renal Disease (MDRD) Study and African American Study of Kidney Disease and Hypertension (AASK) with at least 2 baseline mGFRs from iodine 125-iothalamate urinary clearances, 1 standardized SCr value, and 1 SCysC value.
eGFRs calculated using the 4-variable isotope-dilution mass spectrometry (IDMS)-traceable MDRD Study equation, the Chronic Kidney Disease (CKD) Epidemiology Collaboration (CKD-EPI) SCysC equation, the CKD-EPI SCr-SCysC equation, and mGFRs collected from another prerandomization visit.
A single reference mGFR, average of 2, and average of 3 mGFRs; additional analysis limited to consistent mGFRs (difference <or=25% from reference mGFR).
We found that mGFRs had stable mean values, but substantial variability across visits. Of all mGFRs collected a mean of 62 days apart from the reference visit, 8.0% were outside 30% of the single reference mGFR (1 - P(30)). Estimation equations were less accurate because 12.1%, 17.1%, and 8.3% of eGFRs from the MDRD Study, CKD-EPI SCysC, and CKD-EPI SCr-SCysC equations were outside 30% of the same gold standard (1 - P(30)). However, improving the precision of the reference test from a single mGFR to the average of 3 consistent mGFRs decreased these error estimates (1 - P(30)) to 8.0%, 12.5%, and 3.9%, respectively.
Study population limited to those with CKD.
Imprecision in gold-standard measures of GFR contribute to an appreciable proportion of the cases in which eGFR and mGFR differ by >30%. Reducing and quantifying errors in gold-standard measurements of GFR is critical to fully estimating the accuracy of GFR estimates.
评估基于血清肌酐（SCr）和血清胱抑素 C（SCysC）方程的估算肾小球滤过率（eGFR）的准确性需要金标准 GFR 测量。然而，不精确的测量 GFR（mGFR）对方程误差估计的影响尚不清楚。
诊断测试研究。
来自改良肾脏病饮食研究（MDRD）和非洲裔美国人肾脏病和高血压研究（AASK）的 1995 名参与者，至少有 2 次碘 125-iothalamate 尿清除率、1 个标准化 SCr 值和 1 个 SCysC 值的基线 mGFR。
使用 4 变量同位素稀释质谱法（IDMS）可溯源的 MDRD 研究方程、慢性肾脏病（CKD）流行病学协作组（CKD-EPI）SCysC 方程、CKD-EPI SCr-SCysC 方程计算的 eGFR，以及来自另一次随机前就诊的 mGFR。
单次参考 mGFR、平均 2 次和平均 3 次 mGFR；额外的分析仅限于一致的 mGFR（与参考 mGFR 的差异≤25%）。
我们发现 mGFR 的平均值稳定，但在各次就诊之间存在很大的变异性。在与参考就诊相隔平均 62 天的所有 mGFR 中，有 8.0%超出了单一参考 mGFR 的 30%（1-P（30））。由于 MDRD 研究、CKD-EPI SCysC 和 CKD-EPI SCr-SCysC 方程的 eGFR 中有 12.1%、17.1%和 8.3%超出了同一金标准的 30%（1-P（30）），因此估计方程的准确性较低。然而，将参考测试的精度从单次 mGFR 提高到 3 次一致的 mGFR，分别将这些误差估计（1-P（30））降低到 8.0%、12.5%和 3.9%。
研究人群仅限于患有 CKD 的人群。
金标准 GFR 测量的不精确性导致 eGFR 和 mGFR 差异>30%的情况占相当大的比例。减少和量化金标准 GFR 测量中的误差对于充分估计 GFR 估计的准确性至关重要。
