Hoek Frans J, Kemperman Frits A W, Krediet Raymond T
Academic Medical Center, Department of Clinical Chemistry, Room F1-219, PO Box 22700, 1100 DE Amsterdam, The Netherlands.
Nephrol Dial Transplant. 2003 Oct;18(10):2024-31. doi: 10.1093/ndt/gfg349.
In clinical practice, the glomerular filtration rate (GFR) is often estimated from plasma creatinine. Several studies have shown cystatin C (cys C) to be a better parameter for the diagnosis of impaired renal function. No data are available, however, on the performance of cys C in follow-up of patients, compared with creatinine. Also, comparisons of cys C with the Cockcroft and Gault (C&G) formula for estimation of GFR are few.
Plasma samples were obtained from 93 consecutive patients seen for GFR determination and from 30 patients with diabetes mellitus type 2, of whom 23 were investigated a second time after 2 years. GFR was determined with [125I]iothalamate. Plasma creatinine was determined enzymatically and the creatinine clearance calculated according to C&G. Cys C was measured with a particle-enhanced immunonephelometric method.
GFR correlated with 1/cys C (r = 0.873) as well as with C&G (r = 0.876). The area under the curve (AUC) of the receiver operating curves (ROCs), a measure of diagnostic accuracy, for cys C (0.931) and C&G (0.938) were equal (P = 0.815) and both better than the creatinine AUC (0.848; P = 0.006). Bland and Altman analysis showed that the simple formula GFR = -4.32 + 80.35 x 1/cys C, derived from our data, gave more accurate (P < 0.0001) and more precise (P = 0.024) GFR estimates than obtained with the C&G formula. The day-to-day variation (biological +analytical) for cys C was small (3.1%, SD 2.51%) in diabetic patients. In the follow-up study in diabetic patients, cys C was the parameter which had the best correlation (r = 0.66) with changes in GFR.
Cys C shows a high correlation with GFR. With a very simple formula, cys C gives a good estimate of GFR, more accurate and precise than C&G. Because biological variation is low, cys C gives also a good assessment of GFR changes during follow-up. Cys C is the preferred endogenous parameter for GFR.
在临床实践中，肾小球滤过率（GFR）常通过血浆肌酐来估算。多项研究表明，胱抑素C（cys C）是诊断肾功能受损的更好指标。然而，与肌酐相比，关于cys C在患者随访中的表现尚无数据。此外，将cys C与Cockcroft和Gault（C&G）公式估算GFR的比较也很少。
从93例因GFR测定前来就诊的连续患者以及30例2型糖尿病患者中采集血浆样本，其中23例在2年后进行了第二次调查。用[125I]碘肽酸盐测定GFR。用酶法测定血浆肌酐，并根据C&G公式计算肌酐清除率。用颗粒增强免疫比浊法测定cys C。
GFR与1/cys C（r = 0.873）以及与C&G（r = 0.876）均相关。诊断准确性的指标——受试者工作曲线（ROC）的曲线下面积（AUC），cys C为0.931，C&G为0.938，二者相等（P = 0.815），且均优于肌酐的AUC（0.848；P = 0.006）。Bland和Altman分析表明，根据我们的数据得出的简单公式GFR = -4.32 + 80.35 x 1/cys C，比C&G公式得出的GFR估算值更准确（P < ＜0.0001）、更精确（P = 0.024）。糖尿病患者中cys C的日常变化（生物学 + 分析）较小（3.1%，标准差2.51%）。在糖尿病患者的随访研究中，cys C是与GFR变化相关性最好的参数（r = 0.66）。
cys C与GFR高度相关。通过一个非常简单的公式，cys C能很好地估算GFR，比C&G更准确、精确。由于生物学变异低，cys C在随访期间也能很好地评估GFR变化。cys C是GFR首选的内源性指标。
