Toffaletti John G, McDonnell Elizabeth H
Department of Pathology, Duke University Medical Center, Durham, NC, USA.
Clin Chim Acta. 2008 Sep;395(1-2):115-9. doi: 10.1016/j.cca.2008.05.020. Epub 2008 Jun 3.
To determine the potential sensitivity of several renal function tests for detecting early changes in renal function, we compared the within-individual (W-I) variation over 5 months of serum creatinine, serum cystatin C, and creatinine clearance.
On 31 healthy subjects, blood and timed urine specimens were collected once each month to get 6 collections. Creatinine (enzymatic) in serum and urine and cystatin C (immunonephelometric) in serum were measured and glomerular filtration rate (GFR) by creatinine clearance and the Modification of Diet in Renal Disease (MDRD) equation were calculated. To compare W-I variations between different creatinine methods, we also measured creatinine by both enzymatic and kinetic alkaline picrate methods on 15 sets of frozen samples.
For the 31 volunteers, the mean W-I variations for serum creatinine (5.8%) and cystatin C (5.4%) were both much lower than the W-I variation of creatinine clearance (18.7%). As expected, the MDRD GFR had a similar W-I variation (6.7%) to that of serum creatinine and its values were markedly different than GFR by creatinine clearance. On the 15 sets of frozen samples, the W-I variation of creatinine measured by the enzymatic method (CV 5.2%) was slightly less than by the picrate method (CV 6.2%).
The low W-I variation of both serum cystatin C and serum creatinine suggests that serial measurements of either would detect a changes in renal function earlier than would GFR by creatinine clearance or MDRD equation, which allows reporting only for GFRs<60 ml/min/1.7 m(2). While we measured only creatinine clearance, the large variability, difficulty, and cost of all clearance measurements make them impractical for routine monitoring of patients.
为了确定几种肾功能检测方法在检测肾功能早期变化方面的潜在敏感性，我们比较了血清肌酐、血清胱抑素C和肌酐清除率在5个月内的个体内（W-I）变异。
对31名健康受试者，每月采集一次血液和定时尿液标本，共采集6次。检测血清和尿液中的肌酐（酶法）以及血清中的胱抑素C（免疫比浊法），并通过肌酐清除率和肾脏疾病饮食改良（MDRD）方程计算肾小球滤过率（GFR）。为了比较不同肌酐检测方法之间的W-I变异，我们还对15组冷冻样本同时采用酶法和动力学碱性苦味酸盐法检测肌酐。
对于31名志愿者，血清肌酐（5.8%）和胱抑素C（5.4%）的平均W-I变异均远低于肌酐清除率的W-I变异（18.7%）。正如预期的那样，MDRD GFR的W-I变异（6.7%）与血清肌酐相似，其值与肌酐清除率计算的GFR明显不同。在15组冷冻样本中，酶法检测肌酐的W-I变异（CV 5.2%）略低于苦味酸盐法（CV 6.2%）。
血清胱抑素C和血清肌酐的低W-I变异表明，连续测量二者中的任何一种都比肌酐清除率或MDRD方程计算的GFR能更早地检测到肾功能变化，后者仅适用于GFR<60 ml/min/1.7 m²时的报告。虽然我们仅测量了肌酐清除率，但所有清除率测量的巨大变异性、难度和成本使其不适用于患者的常规监测。
