Tan G D, Lewis A V, James T J, Altmann P, Taylor R P, Levy J C
Oxford Centre for Diabetes, Endocrinology & Metabolism, Oxford, U.K.
Diabetes Care. 2002 Nov;25(11):2004-9. doi: 10.2337/diacare.25.11.2004.
OBJECTIVE-Assessment and follow-up of early renal dysfunction is important in diabetic nephropathy. Plasma creatinine is insensitive for a glomerular filtration rate (GFR) >50 ml/min and creatinine clearance is unwieldy and subject to collection inaccuracies. We aimed to assess the reproducibility, reliability, and accuracy of plasma cystatin C as a measure of GFR ranging from normal to moderate impairment due to type 1 diabetes in the presence of a normal plasma creatinine concentration. RESEARCH DESIGN AND METHODS-A sensitive immunoturbidimetric cystatin C assay was examined in 29 subjects with type 1 diabetes and 11 nondiabetic subjects. Duplicate measurements of the following were collected from each subject, 2 weeks apart: cystatin C, enzymatic plasma creatinine, 24-h creatinine clearance, GFR estimated from plasma creatinine by the Cockcroft-Gault equation, and iohexol clearance as a gold standard. RESULTS-Iohexol clearance ranged from 35 to 132 ml. min(-1). 1.73 m(-2). Plasma cystatin C compared well with the other clinically used tests. The reliability of cystatin C, as assessed by the discriminant ratio, was superior to creatinine clearance (3.4 vs. 1.5, P < 0.001) and the correlation of cystatin C with iohexol clearance (Rs -0.80) was similar to that of creatinine clearance (Rs -0.74) and superior to that of plasma creatinine and the Cockcroft-Gault estimate (Rs -0.54 and 0.66, respectively). Duplicate estimations were used to provide an unbiased equation to convert plasma cystatin C to GFR. CONCLUSIONS-Based on this study, cystatin C is a more reliable measure of GFR than creatinine clearance, is more highly correlated with iohexol clearance than plasma creatinine, and is worthy of further investigation as a clinical measure of GFR in type 1 diabetes.
目的——早期肾功能不全的评估及随访在糖尿病肾病中至关重要。血浆肌酐对肾小球滤过率（GFR）>50 ml/min不敏感，且肌酐清除率操作不便且受收集误差影响。我们旨在评估在血浆肌酐浓度正常的情况下，血浆胱抑素C作为1型糖尿病所致正常至中度肾功能损害GFR测量指标的可重复性、可靠性和准确性。研究设计与方法——在29例1型糖尿病患者和11例非糖尿病患者中检测了一种灵敏的免疫比浊法胱抑素C检测方法。每隔2周从每位受试者收集以下指标的重复测量值：胱抑素C、酶法检测的血浆肌酐、24小时肌酐清除率、根据Cockcroft-Gault方程由血浆肌酐估算的GFR以及作为金标准的碘海醇清除率。结果——碘海醇清除率范围为35至132 ml·min⁻¹·1.73 m⁻²。血浆胱抑素C与其他临床常用检测方法相比效果良好。通过判别比评估，胱抑素C的可靠性优于肌酐清除率（3.4对1.5，P<0.001），且胱抑素C与碘海醇清除率的相关性（Rs=-0.80）与肌酐清除率（Rs=-0.74）相似，优于血浆肌酐和Cockcroft-Gault估算值（分别为Rs=-0.54和0.66）。使用重复估算值得出一个无偏方程，用于将血浆胱抑素C转换为GFR。结论——基于本研究，胱抑素C作为GFR的测量指标比肌酐清除率更可靠，与碘海醇清除率的相关性比血浆肌酐更高，作为1型糖尿病GFR的临床测量指标值得进一步研究。
