Orlando R, Floreani M, Padrini R, Palatini P
Institute of Clinical Medicine, University of Padova, Italy.
Clin Nephrol. 1999 Jun;51(6):341-7.
Discrepant results have been published regarding the suitability of creatinine clearance (C(Cr)) as a measure of glomerular filtration rate (GFR) in cirrhotic patients with normal renal function.
In this study we evaluated the accuracy and precision of measured and calculated C(Cr) as indexes of GFR by comparing their values to those of inulin clearance (C(In)) in 10 healthy subjects and 20 patients with either Child's class A or Child's class C liver cirrhosis.
The accuracy and precision of GFR estimates obtained by measuring C(Cr) were good in all three study groups. The mean values of the C(Cr)/C(In) ratio were 1.05, 1.03 and 1.04, respectively, and the corresponding coefficients of variations were 2.9, 2.9 and 3.8%. A close correlation between C(Cr) and C(In) was also found in each study group (r = 0.98, 0.99 and 0.97, respectively, with p < 0.001 in each case). C(Cr) calculated from serum creatinine by means of the Cockcroft-Gault formula (predicted GFR) proved to be a suitable measure of GFR in normal subjects and patients with Child's class A cirrhosis: the predicted-to-true GFR ratios were 0.93 and 0.94, respectively, CV was 12% in both cases. Moreover, a significant correlation between predicted and true GFR was observed in both groups (r = 0.73, p < 0.02 and r = 0.69, p < 0.025, respectively). On the contrary, in Child's class C cirrhotics, calculated C(Cr) significantly overestimated GFR (predicted-to-true GFR ratio 1.23, CV 20%) and no significant correlation was found between predicted and true GFR (r = 0.58, p > 0.05).
In conclusion, this study shows that measured C(Cr) is a reliable index of GFR in cirrhotic patients, irrespective of the degree of liver dysfunction. Calculated C(Cr) is still an adequate marker of GFR in patients with compensated liver cirrhosis, whereas it overestimates GFR in patients with decompensated cirrhosis. A lower muscle mass, a reduced ability to convert creatine to creatinine, and the presence of ascites are most likely responsible for the overestimation of GFR by the Cockcroft-Gault formula in the latter patients.
关于肌酐清除率（C(Cr)）作为肾功能正常的肝硬化患者肾小球滤过率（GFR）衡量指标的适用性，已发表了不一致的结果。
在本研究中，我们通过将10名健康受试者以及20名Child A级或Child C级肝硬化患者的实测和计算所得的C(Cr)值与菊粉清除率（C(In)）值进行比较，评估了实测和计算所得的C(Cr)作为GFR指标的准确性和精密度。
在所有三个研究组中，通过测量C(Cr)获得的GFR估计值的准确性和精密度均良好。C(Cr)/C(In)比值的平均值分别为1.05、1.03和1.04，相应的变异系数分别为2.9%、2.9%和3.8%。在每个研究组中还发现C(Cr)与C(In)之间存在密切相关性（r分别为0.98、0.99和0.97，每组p均<0.001）。通过Cockcroft-Gault公式由血清肌酐计算得出的C(Cr)（预测GFR）被证明是正常受试者和Child A级肝硬化患者GFR的合适衡量指标：预测GFR与实际GFR的比值分别为0.93和0.94，两种情况下CV均为12%。此外，在两组中均观察到预测GFR与实际GFR之间存在显著相关性（r分别为0.73，p<0.02和r为0.69，p<0.025）。相反，在Child C级肝硬化患者中，计算所得的C(Cr)显著高估了GFR（预测GFR与实际GFR的比值为1.23，CV为20%），并且在预测GFR与实际GFR之间未发现显著相关性（r = 0.58，p>0.05）。
总之，本研究表明，实测C(Cr)是肝硬化患者GFR的可靠指标，与肝功能障碍程度无关。计算所得的C(Cr)在代偿期肝硬化患者中仍是GFR的合适标志物，而在失代偿期肝硬化患者中它高估了GFR。肌肉量较低、肌酸转化为肌酐的能力降低以及腹水的存在很可能是Cockcroft-Gault公式在后者患者中高估GFR的原因。
