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Background: Creatinine and cystatin C concentrations are commonly used to estimate glomerular filtration rate (eGFR) in clinical practice and epidemiological studies. To estimate the influence of different body composition measures on eGFR from creatinine and cystatin C blood concentrations, we compared the associations of different anthropometric and body composition measures with eGFR derived from creatinine (eGFRcreat) and cystatin C (eGFRcystC) blood concentrations., Methods: In a population-based cohort study among 4,305 children aged 6.0 years (95% range 5.7-8.0), we measured weight and height and calculated body mass index (BMI) and body surface area (BSA), and lean and fat mass using dual-energy X-ray absorptiometry. At the same age, we measured creatinine and cystatin C blood concentrations and estimated the GFR., Results: Correlation between eGFR based on creatinine and cystatin C concentrations was r = 0.40 (p value <0.01). Higher BMI was associated with lower eGFRcystC but not with eGFRcreat. Higher BSA was associated with higher eGFRcreat and lower eGFRcystC (p value <0.05). Lean and fat mass percentages were associated with eGFRcreat but not with eGFRcystC., Conclusion: Our findings suggest that both eGFRcreat and eGFRcystC are influenced by BMI and BSA. eGFRcreat is more strongly influenced by body composition than eGFRcystC., (© 2017 S. Karger AG, Basel.)

Background: The aim of this study was to evaluate the performance of selected pediatric estimated glomerular filtration rate (eGFR) equations in relation to the clinical management of children after renal or heart transplantation or post-chemotherapy treatment., Methods: This study was a retrospective cross-sectional analysis of 61 children whose glomerular function (GFR) had been determined using a single-dose inulin clearance (iGFR) method. Eight equations for estimating the GFR were evaluated for bias, agreement, accuracy, and clinical stratification., Results: The outcome of all eight eGFR equations differed from the value determined using the iGFR method, with the mean bias ranging from -3.4 to 20.7 ml/min/1.73 m(2) and 90 % accuracy ranging from 16 to 26 %. All eGFR equations overestimated renal function in patients with decreased kidney function as determined by the iGFR method and underestimated renal function in patients with normal kidney function. Consequently, based on the eGFR values, patients with low GFR values according to the iGFR method were staged in a less severe chronic kidney disease (CKD) category, and patients with normal GFR values according to the iGFR method were staged in a more severe CKD category. The percentage of correctly classified patients ranged from 32.6 to 41.6 %., Conclusions: In our cohort we found the CKiDIII equation to be the best alternative to calculating the GFR using the inulin clearance method, closely followed by the Hoste and the revised Grubb equations. The performances of all eight eGFR equations assessed were moderate at best and only slightly better than the easy-to-do bedside Schwartz equation.

Glomerular filtration rate (GFR) in children can be estimated by the formula GFR=k x BH/Pcr (where BH is body height in centimetres and Pcr is the plasma creatinine concentration in micromoles per litre). For k, several values have been reported: k=38 (Counahan), k=40 (Morris) and k=48.7 (Schwartz). In this study the predictive performance of these formulae was compared with that of newly developed formulae. GFR measurements based on inulin concentration time curves were divided into an index (n=58) and a validation data set (n=48). In the index data set a value for k was derived by application of nonlinear mixed-effect modelling. This approach was also used to develop a formula that better explained the relationship between patient factors and GFR. Bias and precision of all formulae were calculated for the validation data set. In the index data set a value of 41.2 was found for k, which was close to the value k=40 (Morris). Both formulae estimated GFR well (bias <5%; precision 25%). Further modelling of the relationship between patient factors and GFR did not improve the predictive performance. In our hospital GFR was best estimated by the formula with k=40 and k=41.2. It is recommended that the optimal value for k be assessed locally.

The reference method to determine the glomerular filtration rate (GFR) in children is the urinary clearance of inulin during a continuous intravenous infusion. Alternatively, the plasma clearance of inulin can be determined, which does not require urine collection. This study compared the determination of the inulin plasma clearance in 24 pediatric patients by two methods: the single injection and the continuous infusion method. In the single injection method 5000 mg/m(2) inulin was administered as bolus injection, and blood samples were drawn 10, 30, 90, and 240 min after administration. For the continuous infusion method inulin was started overnight and blood samples were collected the next day. The inulin plasma clearance determined by the single injection method was on average 9.7 ml min(-1) 1.73 m(-2) higher than the clearance determined with the continuous infusion method (95% CI: 5.3-14.2). The difference between the two methods was smaller at lower GFRs. The difference in results generated by the two methods in children is small and is considered acceptable in clinical practice. For practical reasons, the single injection method with minimum sampling is preferred.

Evaluates the determination of the glomerular filtration rate (GFR) in children by the inulin single-injection method. Accuracy of results; Plasma concentration-time-decay-curve constructed using the method; Calculation of GFR using a computer software.