The CRISMA (Clinical Research, Investigation, and Systems Modeling of Acute Illness) Laboratory, Department of Critical Care Medicine, University of Pittsburgh, School of Medicine, Pittsburgh, USA.
Nephrol Dial Transplant. 2010 Dec;25(12):3911-8. doi: 10.1093/ndt/gfp766. Epub 2010 Jan 25.
A pre-morbid 'baseline' creatinine is required in order to diagnose and stage acute kidney injury (AKI) using the RIFLE classification. Estimation of baseline creatinine by solving the Modification of Diet in Renal Disease (MDRD) equation assuming a glomerular filtration rate of 75 ml/min/1.73 m(2) has been widely used but never validated.
We analysed four cohorts of intensive care unit (ICU) patients from three centres (two from Pittsburgh and one from Mayo and Austin). Three cohorts consisted of preselected patients without AKI (Pittsburgh 1 n = 1048, Mayo n = 737, Austin n = 333), and measured creatinine values in these cohorts were taken to represent baseline creatinine values. The last cohort (Pittsburgh 2 n = 468) consisted of unselected ICU patients with baseline creatinine values recorded within 1 year before ICU admission. Using the Pittsburgh 1 cohort, we derived an equation using the same anthropometric variables as the MDRD equation: baseline creatinine = 0.74 - 0.2 (if female) + 0.08 (if black) + 0.003 × age (in years). We then compared measured creatinine in the Mayo and Austin cohorts and recorded creatinine in the Pittsburgh 2 cohort to the estimated creatinine from: (i) the MDRD equation; (ii) our new equation; (iii) a gender-fixed creatinine of 0.8 mg/dl for females and 1.0 mg/dl for males.
Using any of the three methods, the median absolute error of the estimates was of the order of 0.1-0.2 mg/dl, and overall accuracy was similar. When the definition of AKI was limited to the severity grades of Injury and Failure, all three methods were able to generate 78-90% reliable results for preselected normal range cohorts, and 63-70% for the unselected cohort of ICU patients.
Estimates of incidence of AKI in the critically ill using RIFLE classification can be affected by the bias and limited accuracy of methods to estimate baseline creatinine. Whenever possible, recorded creatinine values should be used as a reference of baseline. The use of the MDRD equation to estimate baseline creatinine when it is unknown may over- or underestimate some mild (Risk) AKI cases but is unlikely to misclassify patients in Injury and Failure.
使用 RIFLE 分类法诊断和分期急性肾损伤（AKI）需要预先确定的基础肌酐。通过解决假定肾小球滤过率为 75ml/min/1.73m2 的肾脏病饮食改良（MDRD）方程来估计基础肌酐已被广泛应用，但从未经过验证。
我们分析了来自三个中心（两个来自匹兹堡，一个来自梅奥和奥斯汀）的重症监护病房（ICU）患者的四个队列。三个队列由无 AKI 的预选患者组成（匹兹堡 1 队列 n=1048，梅奥队列 n=737，奥斯汀队列 n=333），并采用这些队列中的测量肌酐值作为基础肌酐值。最后一个队列（匹兹堡 2 队列 n=468）由 ICU 入院前 1 年内记录了基础肌酐值的未选 ICU 患者组成。我们使用匹兹堡 1 队列，使用与 MDRD 方程相同的人体测量变量推导出一个方程：基础肌酐=0.74-0.2（女性）+0.08（黑人）+0.003×年龄（岁）。然后，我们将梅奥和奥斯汀队列中的测量肌酐值与从以下方面估计的肌酐值进行比较：（i）MDRD 方程；（ii）我们的新方程；（iii）对于女性为 0.8mg/dl，对于男性为 1.0mg/dl 的固定性别肌酐值。
使用这三种方法中的任何一种，估计值的中位数绝对误差均为 0.1-0.2mg/dl，且整体准确性相似。当 AKI 的定义仅限于损伤和衰竭的严重程度等级时，所有三种方法都能够为预选正常范围的队列生成 78-90%的可靠结果，为未选 ICU 患者队列生成 63-70%的可靠结果。
使用 RIFLE 分类法估计危重症患者 AKI 的发生率可能受到估计基础肌酐的方法的偏差和有限准确性的影响。只要有可能，应使用记录的肌酐值作为基础的参考。当基础肌酐未知时，使用 MDRD 方程估计基础肌酐可能会过高或过低估计某些轻度（风险）AKI 病例，但不太可能错误分类损伤和衰竭的患者。
