比较不同肾小球滤过率计算方法评价儿童慢性肾脏病肾功能的适用性

目的 肾小球滤过率(GFR)是评价肾功能的最好指标,可用直接检测法和公式估算法获得GFR,后者在临床实践中尤为常用,如24 h内生肌酐清除率、Schwartz公式以及Filler公式,但少有对这些计算方法在我国儿童慢性肾脏病(CKD)患者的适用性的研究.方法 选择2002年至2005年在我院住院、且符合入选标准和排除标准的CKD患儿为研究对象.将24 h内生肌酐清除率、Schwartz公式以及Filler公式估算的GFR(eGFR)与99mTc-DTPA肾动态显像(Gates法)测得的GFR(rGFR)进行比较.结果 入选30例患儿(男18例、女12例),平均年龄为9.4岁.CKD1期13例、CKD2期8例、CKD3期8例、CKD4期1例.CKD病因包括结构异常、肾小球肾炎、血管性疾病、肾病综合征和泌尿系结核.Bland-Altman分析显示24 h内生肌酐清除率的eGFR与rGFR的一致性相对最好;由24 h肌酐清除率和Schwartz公式得出的eGFR的准确性较Filler公式好.CKD1期时,由24 h内生肌酐清除率和Schwartz公式得出的eGFR过高估计rGFR,而由Filler公式得出的eGFR过低估计rGFR;CKD2期时,由24 h内生肌酐清除率得出的eGFR过低估计rGFR,而由Schwartz公式和Filler公式得出的eGFR过高估计rGFR.结论 3种公式获得的GFR的估计值与标准方法测得的GFR值之间存在显著差异,有待于今后开发更适用于我国儿童的肾功能估算方法.

Evaluation of the applicability of three prediction equations for estimating glomerular filtration rate in children with chronic kidney disease

Objective Accurate and reliable assessment of renal function is important in the management of children with chronic kidney disease (CKD). Glomerular filtration rate (GFR) is the best index of assessing kidney function. For assessment of GFR, both gold standard tests and prediction equations have been used. The well-known 24-hour endogenous creatinine clearance (Ccr), the Schwartz formula and the Filler formula are increasingly used in daily clinical practice. However, there are few studies on the applicability of these prediction equations for estimating GFR in Chinese children with CKD. The aim of this study was to compare these prediction equations estimating GFR with an isotope clearance method isotope glomerular filtration rate (rGFR)] in such patients. Method Children aged 1-16 years who underwent isotope 99mTc-diethylenetriaminepentaacetic acid (99mTc-DTPA) GFR testing (Gates' method) between the year of 2002 and 2005 were studied retrospectively. GFR was estimated using: ( 1 ) 24-hour Ccr, which was calculated using the standard formula: urine creatinine ( milligrammes per millilitre) × 24-hour urine volume/serum creatinine ( milligrammes per millilitre) × 1440] × 1.73 (m2 )/body surface area ( m2 )];(2) the Schwartz formula, which is: eGFR (ml/min per 1.73 m2) = k × height (centimetres)/serum creatinine ( micromoles per litre), where k is 62 in males at 13 years of age and older, 40 in infants, and 49 in all other children; and (3) the Filler formula, which is: logGFR = 1.962 + 1.123 × log( 1/Cys C)],where cystatin C is measured in milligrammes per litre. Serum and urinary creatinine levels were detected by alkaline kinetic method. Serum cystatin C was analysed by particle-enhanced immunoturbidimetric assay.Bias and precision were evaluated. Result Thirty subjects ( 18 males and 12 females; mean age 9.4 years)fulfilling both inclusion criteria and exclusion criteria were included in this study. The mean (SD) rGFR was 81.57 (36. 92) ml/min per 1.73 m2; 18 subjects were in CKD stage Ⅰ , 8 in CKD stage Ⅱ, 8 in CKD stage Ⅲ, and 1 in CKD stage Ⅳ. Only the mean 24 h Ccr-eGFR was slightly higher than rGFR (0.4 ml/min per 1.73 m2 higher). Within 95% limits of agreement, the maximum absolute value of bias was about 50 ml/min per 1.73 m2. Accuracy ( estimated GFR values within ± 30% of rGFR) for all formulae was poor, ranging from 23.3% to 43.3%. All formulae overestimate or underestimate rGFR in different CKD stages. Conclusion In Chinese children with CKD, there was a significant difference between measured GFR and estimated GFR using 24h Ccr, Schwartz formula and Filler formula. More suitable GFR predictive equations to assess glomerular function of such patients should be developed.