Estimating glomerular filtration rate in children: evaluation of creatinine- and cystatin C-based equations.

BACKGROUND: Glomerular filtration rate (GFR) estimated by creatinine- and/or cystatin C-based equations (eGFR) is widely used in daily practice. The purpose of our study was to compare new and old eGFR equations with measured GFR (mGFR) by iohexol clearance in a cohort of children with chronic kidney disease (CKD). METHODS: We examined 96 children (median age 9.2 years (range 0.25-17.5)) with CKD stages 1-5. A 7-point iohexol clearance (GFR7p) was defined as the reference method (median mGFR 66 mL/min/1.73 m2, range 6-153). Ten different eGFR equations, with or without body height, were evaluated: Schwartzbedside, SchwartzCKiD, SchwartzcysC, CAPA, LMREV, (LMREV + CAPA) / 2, FAScrea, FAScysC, FAScombi, FASheight. The accuracy was evaluated with percentage within 10 and 30% of GFR7p (P10 and P30). RESULTS: In the group with mGFR below 60 mL/min/1.73 m2, the SchwartzcysC equation had the lowest median bias (interquartile range; IQR) 3.27 (4.80) mL/min/1.73 m2 and the highest accuracy with P10 of 44% and P30 of 85%. In the group with mGFR above 60 mL/min/1.73 m2, the SchwartzCKiD presented with the lowest bias 3.41 (13.1) mL/min/1.73 m2 and P10 of 62% and P30 of 98%. Overall, the SchwartzcysC had the lowest bias - 1.49 (13.5) mL/min/1.73 m2 and both SchwartzcysC and SchwartzCKiD showed P30 of 90%. P10 was 44 and 48%, respectively. CONCLUSIONS: The SchwartzcysC and the combined SchwartzCKiD present with lower bias and higher accuracy as compared to the other equations. The SchwartzcysC equation is a good height-independent alternative to the SchwartzCKiD equation in children and can be reported directly by the laboratory information system. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov , Identifier NCT01092260, https://clinicaltrials.gov/ct2/show/NCT01092260?term=tondel&rank=2.

Estimated glomerular filtration rate in stable older kidney transplant recipients-are present algorithms valid? A national cross-sectional cohort study.

Several equations have been developed for estimated glomerular filtration rate (eGFR) in patients with chronic kidney disease (CKD), but none were developed based on data from elderly kidney transplant recipients (KTR). The primary aim of this study was to evaluate different creatinine-based equations in stable elderly KTR. A national cross-sectional study was performed using data from 263 consecutive kidney transplant recipients 60 years or older who performed a routine GFR measurement one year after engraftment. GFR was measured by iohexol clearance calculation based on two samples. eGFR was calculated from a range of different creatinine-based equations using information obtained at the time of GFR measurement. Bias, precision, and accuracy were evaluated for each equation. All equations apart from Nankivell had accuracy (P30) > 80%. The BIS1, FAS, LMRCR , and Cockcroft & Gault equations in recipients older than 70 years and the FAS, LMRCR , and MDRD in recipients 60-69 years old had nonsignificant bias. The CKD-EPI had significant bias in both groups. If one should choose a single equation for follow-up of individual CKD progression in all recipients ≥ 60 years, the FAS or LMRCR equations are probably the best alternatives.

Renal Function Influences Diagnostic Markers in Serum and Urine: A Study of Guanidinoacetate, Creatine, Human Epididymis Protein 4, and Neutrophil Gelatinase-Associated Lipocalin in Children.

BACKGROUND: Impaired renal function may affect the level of diagnostic disease markers. The aim of the study was to investigate the effect of measured glomerular filtration rate (GFR) on 4 diagnostic markers in blood and urine-guanidinoacetate (GAA), creatine (CRE), human epididymis protein 4 (HE4), and neutrophil gelatinase-associated lipocalin (NGAL)-and how this could affect the decision and reference limits. METHODS: We examined 96 children (median age 9.2 years, range 0.25-17.5) with different stages of chronic kidney disease (CKD). GFR [median 65.9 mL · min-1 · (1.73 m2)-1, range 6.3-153] was measured by iohexol clearance using 7 venous blood samples after iohexol injection. Fasting serum and urinary GAA, CRE, HE4, NGAL, and creatinine (crn) were analyzed. After appropriate transformation of the markers, a multiple linear regression analysis examined the influence of age, sex, and measured GFR. RESULTS: The level of GFR significantly affected S-GAA (P = 2 × 10-4) and U-GAA/crn (P = 5 ×10-11), leading to decreased values in renal impairment. GFR did not correlate significantly with the level of CRE and to a minor degree did the U-CRE/crn ratio (P = 0.54 and 0.01, respectively). The level of GFR significantly affected S-HE4 (P = 4 × 10-31) and U-HE4/S-HE4 ratio (P = 2 × 10-21) with increased serum values and decreased U-HE4/S-HE4 ratio in renal impairment. S-NGAL increased with decreasing kidney function (P = 2 × 10-19). CONCLUSIONS: Diagnostic disease markers may be influenced by the renal function, and this must be taken into account when interpreting test results. Decreased renal function could change the level of the marker above or below decision limits, leading to diagnostic misinterpretation. CLINICAL TRIAL REGISTRATION: ClinicalTrials.gov, Identifier NCT01092260, https://clinicaltrials.gov/ct2/show/NCT01092260?term=tondel&rank=2.

Estimating Glomerular Filtration Rate in Kidney Transplant Recipients: Comparing a Novel Equation With Commonly Used Equations in this Population.

BACKGROUND: Assessment of glomerular filtration rate (GFR) is important in kidney transplantation. The aim was to develop a kidney transplant specific equation for estimating GFR and evaluate against published equations commonly used for GFR estimation in these patients. METHODS: Adult kidney recipients (n = 594) were included, and blood samples were collected 10 weeks posttransplant. GFR was measured by 51Cr-ethylenediaminetetraacetic acid clearance. Patients were randomized into a reference group (n = 297) to generate a new equation and a test group (n = 297) for comparing it with 7 alternative equations. RESULTS: Two thirds of the test group were males. The median (2.5-97.5 percentile) age was 52 (23-75) years, cystatin C, 1.63 (1.00-3.04) mg/L; creatinine, 117 (63-220) µmol/L; and measured GFR, 51 (29-78) mL/min per 1.73 m2. We also performed external evaluation in 133 recipients without the use of trimethoprim, using iohexol clearance for measured GFR. The Modification of Diet in Renal Disease equation was the most accurate of the creatinine-equations. The new equation, estimated GFR (eGFR) = 991.15 × (1.120sex/([age0.097] × [cystatin C0.306] × [creatinine0.527]); where sex is denoted: 0, female; 1, male, demonstrating a better accuracy with a low bias as well as good precision compared with reference equations. Trimethoprim did not influence the performance of the new equation. CONCLUSIONS: The new equation demonstrated superior accuracy, precision, and low bias. The Modification of Diet in Renal Disease equation was the most accurate of the creatinine-based equations.