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International consensus supports the development of standardized protocols for measured glomerular filtration rate (mGFR) to facilitate the integration of mGFR testing in both clinical and research settings. To this end, the European Kidney Function Consortium convened an international group of experts with relevant experience in mGFR. The working group performed an extensive literature search to inform the development of recommendations for mGFR determination using 1-compartment plasma clearance models and iohexol as the exogenous filtration marker. Iohexol was selected as it is non-radio labeled, inexpensive, and safe, can be assayed at a central laboratory, and the other commonly used non-radio-labeled tracers have been (inulin) or are soon to be (iothalamate) discontinued. A plasma clearance model was selected over urine clearance as it requires no urine collection. A 1 compartment was preferred to 2 compartments as it requires fewer samples. The recommendations are based on published evidence complemented by expert opinion. The consensus paper covers practical advice for patients and health professionals, preparation, administration, and safety aspects of iohexol, laboratory analysis, blood sample collection and sampling times using both multiple and single-sample protocols, description of the mGFR mathematical calculations, as well as implementation strategies. Supplementary materials include patient and provider information sheets, standard operating procedures, a study protocol template, and support for mGFR calculation., (Copyright © 2024 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Estimating glomerular filtration rate (GFR) is important in daily practice to assess kidney function and adapting the best clinical care of patients with and without chronic kidney disease. The new creatinine-based European Kidney Function Consortium (EKFC) equation is used to estimate GFR. This equation was developed and validated mainly in European individuals and based on a rescaled creatinine, with the rescaling factor (Q-value) defined as the median normal value of serum creatinine in a given population. The validation was limited in Non-Black Americans and absent in Black Americans. Here, our cross-sectional analysis included 12,854 participants from nine studies encompassing large numbers of both non-Black and Black Americans with measured GFR by clearance of an exogenous marker (reference method), serum creatinine, age, sex, and self-reported race available. Two strategies were considered with population-specific Q-values in Black and non-Black men and women (EKFC PS ) or a race-free Q-value (EKFC RF ). In the whole population, only the EKFC PS equation showed no statistical median bias (0.14, 95% confidence interval [-0.07; 0.35] mL/min/1.73m 2 ), and the bias for the EKFC RF (0.74, [0.51; 0.94] mL/min/1.73m 2 ) was closer to zero than that for the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI 2021 ) equation (1.22, [0.99; 1.47]) mL/min/1.73m 2 ]. The percentage of estimated GFR within 30% of measured GFR was similar for CKD-EPI 2021 (79.2% [78.5%; 79.9%]) and EKFC RF (80.1% [79.4%; 80.7%]), but improved for the EKFC PS equation (81.1% [80.5%; 81.8%]). Thus, our EKFC equations can be used to estimate GFR in the United States incorporating either self-reported race or unknown race at the patient's discretion per hospital registration records., (Copyright © 2023 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Precise determination of circulating parathyroid hormone (PTH) concentration is crucial to diagnose and manage various disease conditions, including the chronic kidney disease-mineral and bone disorder. However, the lack of standardization in PTH assays is challenging for clinicians, potentially leading to medical errors because the different assays do not provide equivalent results and use different reference ranges. Here, we aimed to evaluate the impact of recalibrating PTH immunoassays by means of a recently developed LC-MS/MS method as the reference. Utilizing a large panel of pooled plasma samples with PTH concentrations determined by the LC-MS/MS method calibrated with the World Health Organization (WHO) 95/646 International Standard, five PTH immunoassays were recalibrated. The robustness of this standardization was evaluated over time using different sets of samples. The recalibration successfully reduced inter-assay variability with harmonization of PTH measurements across different assays. By recalibrating the assays based on the WHO 95/646 International Standard, we demonstrated the feasibility for standardizing PTH measurement results and adopting common reference ranges for PTH assays, facilitating a more consistent interpretation of PTH values. The recalibration process aligns PTH results obtained from various immunoassays with the LC-MS/MS method, providing more consistent and reliable measurements. Thus, establishing true standardization across all PTH assays is crucial to ensure consistent interpretation and clinical decision-making., (Copyright © 2023 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background and Aims: In hemodialysis patients, monitoring 25-hydroxyvitamin D (25(OH)D) levels is recommended. It is however unclear if monitoring 1,25-dihydroxyvitamin D (1,25(OH) 2 D) levels is interesting., Materials and Methods: We repeatedly measured 1,25(OH) 2 D (DiaSorin Liaison analyser) and 25(OH)D (LCMS/MS) concentrations in patients newly treated by active or native vitamin D to study the impact of such treatments on serum concentrations., Results: Ten patients were included in the native and 12 in the active vitamin D group. In the native group, a significant increase was observed between the baseline and the last 25(OH)D concentrations available (21.65[17.39;25.26] versus 33.49[28.60;40.30] ng/mL, p = 0.0059). The baseline and last available 1,25(OH) 2 D concentrations were not different (12.15[4.25;15.40] versus 11.35[9.72;21.85] pg/mL, p = 0.5566). In the active group, no difference was observed between the baseline and the last 25(OH)D concentrations (51.70[42.97;63.95] versus 50.89[42.02;64.49] ng/mL, p = 0.5186). The same observation was made for 1,25 (OH) 2 D concentrations (25.65[17.05;41.85] versus 28.70[23.36;43.73] pg/mL, p = 0.6221). Using a linear mixed model, a significant change over time was only observed in 25(OH)D serum levels for patients treated by with native vitamin D., Conclusion: Measuring 1,25(OH)2D levels in patients newly treated by active vitamin D does not seem useful in monitoring active vitamin D therapy., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Background and Aims: Patients with inflammatory bowel diseases (IBD) are exposed to drug-related nephrotoxicity and kidney-related extra-intestinal manifestations (EIMs). Patients should be monitored but guidance is lacking in current international recommendations. The objective of the Kidney Function Monitoring in Inflammatory Bowel Disease (MONITORED) initiative was to achieve an expert consensus about monitoring kidney function in IBD., Methods: A literature review was first conducted. Then, an expert consensus meeting, involving 28 attendees representing French-speaking gastroenterologists and nephrologists, was held as part of an academic initiative on May 28, 2021. An anonymous Delphi process was used to discuss and vote on statements. Agreement was defined as at least 75% of participants voting for any one statement., Results: Experts reached consensus on 11 criteria for referral to the nephrologist. Concerning kidney function monitoring, participants unanimously validated the use of serum creatinine with estimation of the glomerular filtration rate via the MDRD or CKD-EPI equations. A blood ionogram and a urine sample with measurement of a protein-to-creatinine ratio were also broadly agreed validated. Experts recommended performing this monitoring at IBD diagnosis, prior introducing a new treatment, and annually for EIMs screening and evaluation of treatment tolerance. An evaluation 3 months after starting mesalamine and then every 6 months was felt necessary, while for biologics an annually monitoring was deemed sufficient., Conclusion: The MONITORED consensus proposed guidelines on how to monitor kidney function in IBD. These recommendations should be considered in clinical practice to preserve kidney function and ensure the best approach to our patients., Competing Interests: Conflict of interest L Guillo declares consulting fees for Abbvie. A Amiot declares counseling, boards, lecture, transports or fees from Abbvie, Hospira, Takeda, Gilead, Biocodex, Janssen, Ferring and MSD. B Caron has received lecture and/or consulting fees from Abbvie, Amgen, Celltrion, Janssen, Takeda. G Boschetti has served as a speaker and advisory board member for Abbvie, Janssen, Ferring, Norgine, Tillotts, Pfizer, Celltrion, Takeda, Amgen, Sandoz. G Bouguen has received lecture fees from Abbvie, Ferring, MSD, Takeda, Otsuka, Amgen, Biogen, Celtrion, Janssen, Tillots and Pfizer and consultant fees from Takeda, Janssen, Mylan, Vifor Pharma and Gilead. JM Gornet has received personal fees from Amgen, Janssen Cilag, Sanofi, Takeda, Roche and Tillots Pharma. J Bonnet has received consulting fees for Amgen. L Vuitton has received lecture fees from Abbvie, MSD, Takeda, Ferring, Janssen and Pfizer, and research grants from MSD, Takeda and Pfizer. M Nachury received board membership, consultancy, or lecture fees from Abbvie, Adacyte, Amgen, Arena, CTMA, Celltrion, Ferring, Fresenius-Kabi, Janssen, Mayoli-Spindler, MSD, Pfizer, Takeda. M Uzzan has served as a speaker for Janssen and Abbvie. M Serrero declares lecture and consulting fees for Abbvie, Celltrion, Ferring, Janssen, MSD, Takeda and Tillotts. L Peyrin-Biroulet has served as a speaker, consultant and advisory board member for Merck, Abbvie, Janssen, Genentech, Mitsubishi, Ferring, Norgine, Tillotts, Vifor, Hospira/Pfizer, Celltrion, Takeda, Biogaran, Boerhinger-Ingelheim, Lilly, HAC- Pharma, Index Pharmaceuticals, Amgen, Sandoz, For- ward Pharma GmbH, Celgene, Biogen, Lycera, Samsung Bioepis, Theravance. The remaining authors declare no conflict of interest., (Copyright © 2021 Editrice Gastroenterologica Italiana S.r.l. Published by Elsevier Ltd. All rights reserved.)

Introduction: Several clinical settings require an accurate estimation of the physiologically expected extracellular fluid volume (ECFV). We aimed to analyze the performances of existing ECFV-estimating equations and to develop a new equation., Methods: The performances of 11 ECFV-estimating equations were analyzed in 228 healthy kidney donor candidates (Bichat Hospital, Paris, France) who underwent ECFV measurement using the distribution volume of 51 Cr-labeled EDTA ( 51 Cr-EDTA). An equation was developed using a penalized linear modeling approach (elastic net regression) and externally (Tenon Hospital, Paris, France, N =  142) validated., Results: Participants from Bichat (mean age 45.2 ± 12.0 years, 43.0% men) and Tenon (47.8 ± 10.3 years, 29.6% men) hospitals had a mean measured ECFV of 15.4 ± 2.8 l and 15.1 ± 2.1 l, respectively. Available ECFV-estimating formulae have highly variable precision and accuracy. The new equation incorporating body weight, height, sex, and age had better precision and accuracy than all other equations in the external validation cohort, with a median bias of -0.20 (95% CI: -0.35 to -0.05) l versus -2.63 (-2.87 to -2.42) l to -0.57 (- 0.83 to -0.40) l and 0.21 (0.12 to 0.43) l to 2.89 (2.65 to 3.11) l, for underestimating and overestimating equations, respectively, an interquartile range for the bias of 0.88 (0.70 to 1.08) l versus 0.91 (0.71 to 1.20) l to 1.93 (1.67 to 2.25) l, and an accuracy within 10% of 90.9% (83.8 to 94.4) versus 88.0% (81.0 to 92.3) to 8.5% (4.2 to 13.4). These results were consistent across subgroups defined by sex, body mass index (BMI), body surface area (BSA), age, and ethnicity., Conclusion: We developed and validated a new equation to estimate the individual reference value of ECFV, which is easily usable in clinical practice. Further validation in cohorts including individuals of extreme age and corpulence remains needed., (© 2022 International Society of Nephrology. Published by Elsevier Inc.)

The CKD-EPI creatinine-based estimation equation for glomerular filtration rate (GFR) cannot be used in children, overestimates GFR in young adults, and its combination with the KDIGO recommended pediatric CKiD (Schwartz bedside) equation causes implausible increases in estimated GFR when switching from pediatric to adult care. By establishing sex-specific creatinine growth curves for children and young adults, creatinine levels of children and young adults below age 40 years were adjusted with 40 as assigned age and applied in the CKD-EPI equation. Validation was performed in 4005 children (2-17 years) and 3309 young adults (18-39 years) using metrics based on bias, precision, and accuracy including percentage of estimates within 30% (P 30 ) of measured GFR (mGFR). Comparisons were made with the CKiD and Schwartz-Lyon equations in children. CKD-EPI with age-adjusted creatinine instead of actual age and creatinine led to extensive improvements in bias, precision, and accuracy at all ages, in both sexes and at all levels of mGFR. At mGFR below and above 75 mL/min/1.73m 2 , the P 30 increased from 12% to 75% and 33% to 88% in children, respectively, and from 56% to 73% and 83% to 92% in young adults, respectively. In children adjusted CKD-EPI was more accurate than CKiD, especially above mGFR 75 mL/min/1.73m 2 (P30 88% vs. 82%), while Schwartz-Lyon was more accurate than adjusted CKD-EPI at mGFR below 75 mL/min/1.73m 2 (P30 81% vs. 75%). Thus, the proposed strategy based on age-adjusted creatinine in children and young adults makes the CKD-EPI equation applicable across the full spectrum of age and kidney function., (Copyright © 2020 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Introduction: Glomerular filtration rate (GFR) is measured from the late plasma disappearance curve of an exogenous tracer, after correction for the early decay-corresponding to the distribution of the tracer-using various equations. These equations display the highest discrepancies in the GFR range above 90 ml/min per 1.73 m 2 , and their respective performances against a reference, urinary GFR measurement are unclear., Methods: In patients with mGFR >90 ml/min per 1.73 m 2 from 6 different cohorts, we compared GFR obtained from the plasma clearance of iohexol or 51 Cr-ethylenediamine tetraacetic acid (EDTA), after correction using Chantler (C), Bröchner-Mortensen (BM), Fleming (F), Jodal-Bröchner-Mortensen (JBM), and Ng (N) equations, with urinary clearance of the same tracers or inulin., Results: In 438 participants (median age 41 [39-42] years, 43% women), the median urinary clearance was 100.8 (94.7-112.6) ml/min per 1.73 m 2 . Plasma clearances using the correction equations were 105.7 (96.8-119.2), 102.4 (95.2-112.9), 100.7 (93.6-111.1), 102.6 (95.2-113.4), and 106.0 (98.2-117.6) ml/min per 1.73 m 2 for C, BM, F, JBM, and N, respectively. Concordance correlation coefficients between plasma and urinary clearances were poor for all equations. Compared with urinary clearances, BM, F, and JBM displayed the best accuracy within 10% (73%, 72%, and 71%, respectively, vs. 63% and 66% for C and N), whereas BM and JBM had the lowest median biases. Accuracy of all equations was especially low in the hyperfiltration range (urinary clearance >130 ml/min per 1.73 m 2 )., Conclusion: The BM and JBM equations displayed the best overall performances to correct for the early disappearance curve. Results of these equations should be interpreted with caution, especially in the highest GFR range., (© 2021 International Society of Nephrology. Published by Elsevier Inc.)

Chronic kidney disease (CKD) is defined as abnormalities of kidney structure and function proven to be chronic. The prevalence of CKD in the majority of studies is 10%-16%, neglecting the chronicity character. Jonsson et al., in a nationwide study defining CKD adhering strictly to Kidney Disease: Improving Global Outcomes (KDIGO) criteria, found a clearly lower prevalence of CKD (6%). This indicated that to obtain a correct CKD prevalence, one should start by correctly applying the KDIGO guidelines., (Copyright © 2020 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Introduction: Non-oxidized (n-ox) PTH could better reflect PTH activity. We have evaluated the evolution of n-ox PTH and intact PTH (iPTH) in hemodialyzed (HD) patients over a period of 1 year., Material and Methods: We measured iPTH and n-ox PTH in 66 stable HD patients and we measured iPTH and n-ox PTH at baseline and after 1, 3, 6 and 12 months. We considered that no significant changes in iPTH and n-ox PTH occurred if two consecutives measurements of iPTH and n-ox PTH for the same patient remained in the baseline value ±43%. We also considered that changes over time were concordant if both values of the same patients increased or decreased together (in the same direction) by more than 43%., Results: The median [p25; p75] was 229.4 [1.5,4; 352.5] pg/mL for iPTH and 24.4 [15,1; 38.7] pg/mL for n-ox PTH. N-ox PTH fraction represented 11.3 [9.0; 13.7]% of the total iPTH and the ratio n-oxPTH/iPTH ranged from 5.1 to 35.7%. After 1 year, 84% of the patients presented a perfect concordance of the evolution of the 2 moieties and no severe discordance was noticed., Conclusions: The percentage of n-ox PTH is stable over time in stable HD patients., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2020 Elsevier B.V. All rights reserved.)

Sclerostin is sometimes presented as a promising biomarker in assessing bone health both in the general population and chronic kidney disease patients. However, it is still unclear whether it has any true added value compared to existing bone biomarkers in predicting bone turnover and/or bone density in chronic kidney disease patients. A wealth of papers has been published to evaluate the association between sclerostin and vascular calcifications development or even as prognostic biomarker for mortality, but often with conflicting results. Standardization and harmonization of analytical techniques is a prerequisite to advance clinical knowledge in sclerostin., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Introduction: Determination of creatinine and estimation of Glomerular Filtration Rate (GFR) rapidly before injection of contrast media provides early detection of high-risk patients for acute kidney failure. Hence, a rapid point-of-care (POC) device (result in 30 s) allowing creatinine measurement and eGFR could be of interest. To validate this method, we considered a population referred for measuring GFR., Methods: Iohexol plasma clearance was used to measure GFR. For each subject, enzymatic creatinine was quantified with two different devices: in plasma with the Roche Cobas analyzer and in capillary blood with the Nova Biomedical POC device. Both values of creatinine were used in the CKD-EPI equation for estimated glomerular filtration rate (eGFR). eGFR using POC was compared to eGFR using Cobas and to mGFR by Passing Bablok regression, calculation of bias, precision and accuracy (or concordance) within 30%. Also, we calculated the rate of discrepant staging (eGFR >60 or ≤ 60 when mGFR is actually ≤60 and > 60) with both creatinine methods., Results: 120 subjects (52 ± 13 years, 49% of women) were included. Mean mGFR was 77 ± 27 mL/min/1.73m 2 with 29 patients presenting mGFR <60 mL/min/1.73m 2 . Passing- Bablok regression comparing eGFR obtained with the POC and the Cobas was: eGFR POC  = -0.1 (95% CI: -7.4; 3.0) + 1.06 (95% CI: 1.00; 1.15) x eGFR COBAS . Mean bias was 3.7 ± 14.1 mL/min/1.73m 2 . Concordance within 30% was 82%. Compared to mGFR, Passing-Bablok with POC was: eGFR POC  = -11.5 (95% CI: -22.9; -0.7) + 1.15 (95% CI: 1.02; 1.29) x mGFR. Mean bias was 0.1 ± 17.6 mL/min/1.73m 2 . Accuracy within 30% was 81%. Between eGFR COBAS and mGFR, mean bias was -3.7 ± 12.5 mL/min/1.73m 2 . Accuracy within 30% was 95%. With POC (and Cobas), 3.3% (0.8%) of patients would have been considered with GFR > 60 mL/min/1.73m 2 whereas mGFR it was ≤60 and 10% (9.2%) of them would have been considered with GFR ≤60 mL/min/1.73m 2 when mGFR was >60., Conclusion: Creatinine measured with the POC has an acceptable performance when used with the CKD-EPI equation to estimate GFR. Its ability to detect GFR <60 mL/min/1.73m 2 is not significantly different from the classical Roche assay. StatSensor Creatinine (Nova Biomedical) can be used for GFR screening before contrast media injection., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Glomerular filtration rate (GFR) is the best index for kidney function; however, the applicability of GFR estimating equations in sub-Saharan African populations remains unclear. In a cross-sectional study of adults living in Kinshasa, Democratic Republic of Congo (n=210) and Abidjan, Ivory Coast (n=284), we evaluated the performance of creatinine and cystatin C-based equations using plasma clearance of iohexol as the reference standard. The race coefficient did not improve the performance of creatinine-based GFR estimates; in fact, both the Modification of Diet in Renal Disease (MDRD) and Chronic Kidney Disease Epidemiology (CKD-EPI) equations performed better without the race coefficient in participants with GFR ≥60 mL/min/1.73m 2 . The CKD-EPI and Full Age Spectrum (FAS) equations were unbiased and had similar precision (SD of 17.9 versus 19 mL/min/1.73 m 2 ) and accuracy within 30% (P30, 86.7% versus 87.4%) in participants with GFR ≥60 mL/min/1.73m 2 . Both equations performed poorly in the subgroup with measured GFR < 60 mL/min/1.73m 2 (n=80), but the FAS equation had smaller bias (-4.8 mL/min/1.73m 2 versus -7.7 mL/min/1.73m 2 for CKD-EPI) and higher P30 (56.3% versus 31.3% for CKD-EPI). The corresponding equations including cystatin C alone or in combination with creatinine had similar performance. In a sub-Saharan African population, adjustment for race did not improve the performance of GFR estimating equations. The creatinine-based FAS and CKD-EPI equations performed reasonably well and were comparable when GFR was ≥ 60 mL/min/1.73m 2 . Cystatin C did not improve performance. The FAS equation may be preferable when GFR is < 60 mL/min/1.73m 2 , but this should be confirmed in larger studies., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

The current Kidney Disease Improving Global Outcomes (KDIGO) guidelines recommend the use of the bedside creatinine-based Chronic Kidney Disease in Children (CKiD) equation to estimate glomerular filtration rate (GFR) in children and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation in adults. However, this approach causes implausible changes in estimated GFR (eGFR) at the transition from pediatric to adult care. We investigated the performance of the KDIGO strategy and various creatinine-based eGFR equations in a cross-sectional dataset of 5,764 subjects (age 10-30 years), using directly measured GFR (mGFR) as reference. We also evaluated longitudinal GFR slopes in 136 subjects who transitioned to adult care. Implausible changes in eGFR resulted from the large overestimation (bias=+21 mL/min/1.73m 2 ) and poor precision of the CKD-EPI equation in the 18-20 year age group, compared to CKiD in the 16-18 year age group (bias=-2.7 mL/min/1.73m 2 ), resulting in a mean change of 23 mL/min/1.73m 2 at the transition to adult care. Averaging the CKiD and CKD-EPI estimates in young adults only partially mitigated this issue. The Full Age Spectrum equation (with and without height), the Lund-Malmö Revised equation, and an age-dependent weighted average of CKiD and CKD-EPI resulted in much smaller changes in eGFR at the transition (change of 0.6, -2.1, -0.9 and -1.8 mL/min/1.73m 2 , respectively). The longitudinal analysis revealed a significant difference in average GFR slope between mGFR and the KDIGO strategy (-2.2 vs. +2.9 mL/min/1.73 m 2 /year), which was not observed with the other approaches. These results suggest that the KDIGO recommendation for GFR estimation at the pediatric-adult care transition should be revisited., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

While direct measurements of glomerular filtration rate (GFR) provide the most accurate evaluation of pre-donation kidney function, guidelines do not systematically require the use of a reference method. We evaluated whether and to what extent relying upon creatinine-based estimating equations (eGFR) rather than direct measurement of GFR (mGFR) alters the selection of potential living donors. We compared the impact of 4 equations (the MDRD study equation, the CKD-EPI equation, the revised Lund-Malmö equation, and the full age spectrum [FAS] equation) on the evaluation of 2733 potential donors with GFR measured by reference methods. We also considered the impact of using either absolute or age-adapted GFR thresholds. The CKD-EPI and FAS equations had the best performances (P10 of 50.6% and 47.8%; P30 of 94.4% and 93.1%, respectively) and led to the lowest proportion of improperly evaluated candidates. Misclassification was more frequent when GFR adequacy was defined as an absolute threshold of 90 ml/min/1.73m 2 as compared to an age-adapted definition (26% and 5%, respectively). Interpretation of eGFR according to an absolute threshold of 90 ml/min/1.73m 2 identified 1804 candidates eligible to donate, compared to 2648 when mGFR was interpreted with age-adapted thresholds. We conclude that creatinine-based estimates cannot substitute for direct GFR measurement to evaluate candidates for kidney donation. When reference methods for direct GFR measurement are not available, our data suggest that a strategy based on age-adapted eGFR values estimated with either the CKD-EPI or FAS equation should be preferred., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Recommendations on the glomerular filtration rate (GFR) threshold compatible with living kidney donation are not agreed upon. The recent KDIGO guidelines suggested a reset of the conventional cutoff value of 80 to 90 mL/min/1.73 m 2 . While GFR physiologically declines with age, it is unclear whether and how age should be taken into account for selecting acceptable pre-donation GFR. In this multicenter retrospective study encompassing 2007 kidney donors in France, we evaluated the impact of age using two threshold measured GFR (mGFR)s (80 and 90 mL/min/1.73 m 2 ). Three groups of donors were defined according to baseline mGFR: below 80, 80-89.9 and 90 mL/min/1.73 m 2 or more. Thirty-two percent of donors were selected despite an mGFR below 90 mL/min/1.73 m 2 . Donors with the lowest mGFR were significantly older (60 ± 9 vs. 47 ± 11 years) and this applied to both male and female donors. The lifetime-standardized renal reserve, defined as the pre-donation mGFR value divided by the expected number of remaining years of life, was similar irrespective of baseline mGFR groups. Similar results were obtained when eGFR was used instead of mGFR. Finally, in a subgroup of 132 donors with repeated mGFR five years after donation, the magnitude of mGFR decrease was similar in all groups (-34.3%, -33.9%, and -34.9% respectively). Thus, the decision to accept individuals with mGFR lower than 90 mL/min/1.73 m 2 for kidney donation is highly dependent on the age of the candidate. Hence, threshold values lower than 90 mL/min/1.73 m 2 are reasonable for older donors. Age-calibrated mGFR may improve efficiency of the selection process., (Copyright © 2018 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Serum creatinine (Scr) is the major contributing variable in glomerular filtration rate (GFR) estimating equations. Serum cystatin C (ScysC) based GFR estimating (eGFR)-equations have also been developed. The present study investigates the relation between 'rescaled' levels of these renal biomarkers (with reference interval of [0.67-1.33]) and measured GFR (mGFR)., Methods: We evaluated the diagnostic ability to detect impaired kidney function of the rescaled renal biomarkers in 8584 subjects from 12 cohorts with measured GFR, standardized Scr and ScysC. We calculated sensitivity and specificity of the rescaled biomarkers to identify kidney disease, with reference to a fixed (60mL/min/1.73m 2 ) as well as an age-dependent threshold for mGFR., Results: The upper reference limit of 1.33 for rescaled renal biomarkers is closely related to the age-dependent threshold for defining kidney status by mGFR with sensitivity and specificity for the rescaled biomarkers close to 90% for all ages. If the fixed threshold of 60mL/min/1.73m 2 for mGFR is used, then lower specificity in children and sensitivity in older adults are observed., Conclusions: Impaired kidney function can be diagnosed by rescaled renal biomarkers instead of eGFR-equations using the fixed threshold of 1.33 for all ages, consistent with an age-dependent threshold of mGFR., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objectives: To evaluate concordance between glomerular filtration rate (GFR) estimates (Cockcroft and Gault, modification of diet in renal diseases, chronic kidney disease epidemiology study group equations) for drug dosing in HIV-infected patients., Patients and Methods: We performed a monocentric study. GFR was measured using the gold standard method (plasma clearance of iohexol) in 230 HIV-infected patients. Concordance rate was evaluated between measured GFR (mGFR) and estimated GFR (eGFR) for different GFR categories (GFR>90 mL/min, GFR<90 mL/min, GFR>70 mL/min, and GFR<70 mL/min). MDRD and CKD-EPI were used with and without indexation to body surface area (BSA)., Results: Mean age was 48±10 years, mean mGFR was 101±26 mL/min. Concordance between mGFR and eGFR estimated with CG, CKD-EPI (indexed and not indexed to BSA), or MDRD equations (not indexed to BSA) was similar (73%, 73%, 74%, and 73% respectively) for a breakpoint value of 90 mL/min for GFR. At this value, the concordance rate between mGFR and MDRD indexed to BSA was significantly lower (65%, P<0.05). Using 70 mL/min of GFR as the breakpoint value, all equations had similar concordance rates with mGFR (with or without indexation to BSA)., Conclusion: CKD-EPI equation has the same concordance with GFR and with CG when used for drug dosing., (Copyright © 2017 Elsevier Masson SAS. All rights reserved.)

Objective: Bone changes are increasingly described after burn. How bone markers could help to detect early bone changes or to screen burn patients at higher risk of demineralization is still not made clear. We performed an observational study assessing the changes in serum bone markers after moderate burn., Methods: Adults admitted in the first 24h following burn extended on >10% body surface area were included. Serum levels of collagen type 1 cross-linked C-telopeptide (CTX), tartrate-resistant acid phosphatase 5b (TRAP), type 1 procollagen N-terminal (P1NP) and bone alkaline phosphatase (b-ALP) were measured at admission and every week during the first month. Data are expressed as median [min-max]., Results: Bone markers were measured in 20 patients: 18 men, 2 women (including one post-menopausal). Age was 46 [19-86] years old, burn surface area reached 15 [7-85] %. Twelve patients completed the study. All biomarkers mainly remained into normal ranges during evolution. A huge variability was observed regarding biomarkers evolution. Patient's evolution was not linear and could fluctuate from a decrease to an increase of blood concentrations. There was not necessarily a consistency between the two formation or the two resorption markers. Variations observed between two consecutive measurements were lesser than the accepted critical difference in almost one third of the cases., Conclusions: Considering available data, role and interest of bone markers in management of burn related bone disease remain unclear., (Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.)

Background: Chronic kidney disease (CKD) is diagnosed and explored through the determination of the glomerular filtration rate (GFR). Our goal was to develop a simple LC-MS method for the determination in serum of 2 popular GFR markers, contrast agents iohexol and iothalamate, for routine use and comparison studies between the two markers. A similar contrast agent, ioversol, was used as an internal standard and the method underwent a rigorous validation protocol based on β-expectation tolerance intervals., Methods: We adapted the HPLC-UV method from Cavalier et al. to our LC-MS system. Data treatment for the validation was performed using Multiquant 3.0 (Sciex, Framingham, MA, USA) and e.noval 3.0 software (Arlenda, Liège, Belgium)., Results: According to the validation results our method will give accurate and reliable results for concentrations ranging from 6.8 to 250μg/ml for iohexol and 6.15μg/ml to 250μg/ml for iothalamate. In our practice these intervals are sufficient to determine both compounds in most patient samples. Samples with higher detected concentrations can always be diluted into range., Conclusion: With its internal standard and extensive validation, our method is now ready for routine and clinical research use., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Introduction: Fibroblast growth factor 23 (FGF23) is a key regulator in phosphate and vitamin D metabolism When measured with c-terminal assay, it has been shown to be increased following burn. Progress in understanding FGF23 physiology has emphasized the importance of assessing the intact form of FGF23., Methods: The present cohort study is a complementary analysis of a previously published work. Patients >18 years, admitted within 24h after injury with burn surface area (BSA) >10% were included. C-terminal (c-term) and intact (i) FGF23 assay were performed at admission and every week during 4 weeks of follow-up. Inflammation and iron status were assessed at the same time points., Results: Twenty patients were initially included and 12 were followed until day 28. The c-term FGF23 tended to gradually increase during the 4 weeks of follow-up while iFGF23 was quite stable into normal ranges. Iron status showed a typical inflammatory profile. C-term FGF23 was significantly positively correlated with c-reactive protein (CRP) and negatively correlated with iron levels. iFGF23 was not correlated with CRP or iron., Conclusion: FGF23 status following burn is characterized by a dissociation between c-term FGF23 and iFGF23. The hypothesis of an increased cleavage may be raised. Respective role of inflammation and iron levels in such deregulation need to be specified. Both c-term and intact assays should be performed in further studies aiming to increase knowledge on FGF23 regulation and effects in burn patients., (Copyright © 2016 Elsevier Ltd and ISBI. All rights reserved.)

Background: Cystatin C is increasingly used in glomerular filtration rate (GFR) estimation equations. The dependence of cystatin C results upon the analytical method has been a major source of controversy., Methods: Cystatin C was measured with non-standardized turbidimetric Roche Generation 1 and standardized nephelometric Siemens assays in 3666 and additionally with standardized Roche Generation 2 and Siemens in 567 blood samples of the Berlin Initiative Study. Cystatin C-based GFR was assessed with CKD-EPIcys (Chronic Kidney Disease Epidemiology) and CAPA (Caucasian, Asian, Pediatric, Adult) equations and the impact of the assays on GFR estimation was determined. Equation performance compared to measured GFR was evaluated., Results: Concordance of Roche Gen2 and Siemens was high with median difference of 0.003 ± 0.13 mg/L (limits of agreement: -0.12 to 0.12) and Passing Bablok correlation was essentially perfect. Roche Gen1 assay showed worse concordance with Siemens: median difference was 0.08 ± 0.13 mg/L (limits of agreement: -0.18 to 0.34) and correlation was inferior. Mean difference (± SD) of estimated GFRCKD-EPIcys was 0 ± 4 mL/min/1.73 m(2) for Gen2 and Siemens compared to -5 ± 8 with Gen1. Performance of GFR estimating equations was not influenced by the choice of Siemens or Gen2 assays., Conclusions: Standardization of Roche Gen2 assay improved accuracy of cystatin C measurement compared to Siemens. It suggests only negligible method bias and results in equal performance of both assays when estimating GFR indicating that successful calibration has led to major progress in cystatin C analysis., (Copyright © 2016 Elsevier B.V. All rights reserved.)

The measurement of calcitriol [1,25(OH2)D], is important for the differential diagnosis of several disorders of calcium/phosphorus metabolism but is time-consuming and tricky. We measured serum calcitriol with a new automated direct assay on the Liaison XL platform in 888 healthy French Caucasian subjects aged 18-89 years, 32 patients with a surgically-proven PHPT, 32 pregnant women at the end of the first and at the end of the third trimester, and 24 dialysis patients before and after one year of supplementation with vitamin D3 or placebo. The mean calcitriol concentration (±SD) in the healthy population was 52.9±14.5 ng/L with a 95% CI interval of 29-83.6 ng/L. In PHPT patients, calcitriol concentration was 81.6±29.0 ng/L, 15 of them (46.9%) having a concentration >83.6 ng/L. In pregnant women, calcitriol was 80.4±26.4 ng/L at the end of the first trimester, and 113.1±33.0 ng/L at the end of the third trimester, 12 (37.5%) and 26 (81.3%) of them having a calcitriol concentration >83.6 ng/L at the first and third trimesters respectively. In 14 dialysis patients, calcitriol was 9.5±7.7 ng/L and rose to 19.3 ng/L after one year of supplementation with 50,000 IU vitamin D3/month. In 10 other dialysis patients, calcitriol was 9.9±2.9 ng/L and remained stable (12.4±3.7 ng/L) after one year of placebo. In conclusion, this new automated calcitriol assay, in addition to presenting excellent analytical performances, gives the expected variations in patients compared to "normal" values obtained in an extensive reference population., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Sclerostin, an inhibitor of the Wnt signaling pathway, inhibits bone formation. In a study of vascular biopsies of patients undergoing kidney transplantation, Qureshi et al. demonstrate that circulating sclerostin levels are associated with vascular calcification (VC). This adds to an emerging body of literature implicating sclerostin as a key link between chronic kidney disease-mineral and bone disorder and cardiovascular disease. Some confounders of this association remain, and the mechanisms by which sclerostin promotes VC have yet to be elucidated.

The KDIGO guidelines propose a new approach to diagnose chronic kidney disease (CKD) based on estimated glomerular filtration rate (GFR). In patients with a GFR value comprised between 45 and 59 mL/min/1.73 m(2) as estimated by the CKD-EPI creatinine equation (eGFRcreat ), it is suggested to confirm the diagnosis with a second estimation using the CKD-EPI cystatin C-based equations (eGFRcys /eGFRcreat-cys) . We sought to determine whether this new diagnostic strategy might extend to kidney transplant recipients (KTR) and help to identify those with decreased GFR. In 670 KTR for whom a measured GFR was available, we simulated the detection of CKD using the two-steps approach recommended by the guidelines in comparison to the conventional approach relying on creatinine equation. One hundred forty-five patients with no albuminuria had eGFRcreat between 45 and 59 mL/min/1.73 m(2) . Among them, 23% had inulin clearance over 60 mL/min/1.73 m(2) and were thus incorrectly classified as CKD patients. When applying the Kidney Disease: Improving Global Outcomes (KDIGO) strategy, 138 patients were confirmed as having a GFR below 60 mL/min with eGFRcreat-cys . However, 21% of them were misclassified in reference to measured GFR. Our data do no not support the use of cystatin C as a confirmatory test of stage 3 A CKD in KTR., (© Copyright 2015 The American Society of Transplantation and the American Society of Transplant Surgeons.)

Even if the first assay for parathyroid hormone (PTH) was published in the early 1960s, its determination remains a challenge even today. Indeed, in the circulation, PTH is present in its active form (PTH 1-84), but many PTH fragments can also be present. These fragments accumulate when renal function declines and are recognized, at different extents, by the 2nd generation ("intact") PTH assays that are widely used in the clinical laboratories. Some assays, called "3rd generation PTH" do not recognize these fragments, but are not available everywhere. Hence, different problems are also linked with PTH determination. Among them, one can cite the lack of a reference method, the lack of standardization of the assays and, sometimes, the lack of consistent reference range. We can also point out stability problems and a large intra-individual variation. A workgroup is working on these problems under the auspices of the IFCC and we hope that some of these problems will be resolved in the next years. In this article, we will discuss all the possible issues of PTH determination., (Copyright © 2015. Published by Elsevier Masson SAS.)

Acute cardiorenal syndrome (CRS) corresponds to an association of acute heart failure and a worsening of renal function. The detection of acute kidney injury (AKI) unfortunately occurs at a late stage of CRS, leading to an increased mortality of the patients. In this review, we described the pathophysiology of CRS and discussed the potential interest of biochemical biomarkers (namely creatinine, cystatin C, NGAL, KIM-1, fatty acid binding protein, Nacetyl-β-D-glucosaminidase and IL-18) that could potentially help to detect AKI earlier and thus reduce the morbi-mortality of the patients suffering from CRS., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The link between vascular calcification (VC) and increased mortality is now well established. Over time, as clinical importance of this phenomenon has begun to be fully considered, scientists have highlighted more and more physiopathological mechanisms and signaling pathways that underlie VC. Several conditions such as diabetes, dyslipidemia and renal diseases are undoubtedly identified as predisposing factors. But even if the process is better understood, many questions still remain unanswered. This review briefly develops the various theories that attempt to explain mineralization genesis. Nonetheless, the main purpose of the article is to provide a profile of the various existing biomarkers of VC. Indeed, in the past years, a lot of inhibitors and promoters, which form a dense and interconnected network, were identified. Given importance to assess and control mineralization process, a focusing on accumulated knowledge of each marker seemed to be necessary. Therefore, we tried to define their respective role in the physiopathology and how they can contribute to calcification risk assessment. Among these, Klotho/fibroblast growth factor-23, fetuin-A, Matrix Gla protein, Bone morphogenetic protein-2, osteoprotegerin, osteopontin, osteonectin, osteocalcin, pyrophosphate and sclerostin are specifically discussed., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Interpretation of 25OH-D measurement during critical care (CC) may be problematic due to variations of binding protein concentrations (albumin, ALB, and vitamin D binding protein, VDBP). Determination of free 25OH-D concentration may thus be relevant in CC patients. The aim of this observational study was to evaluate effects of an acute hemodilution on vitamin D (VD) status., Methods: Blood samples were obtained before (T1) and after a crystalloid load (T2) administered at anesthesia induction for minor surgery. 25OH-D was measured with LC-MS/MS and with 3 immunoassays (IA): DiaSorin Liaison, IDS iSYS and bioMérieux Vidas. VDBP was measured with the R&D Elisa and ALB on Cobas. Free 25OH-D was calculated using published formula. Accuracy of each 25OH-D IA was calculated as the percentage of IA values within 20% of their respective LC-MS/MS values. Performances of the three AI were compared with LC-MC/MS using Bland-Altman analysis., Results: Twenty adults were included. Compared to T1 values, VDBP, ALB and LC-MS/MS values decreased in parallel by a mean of 23% at T2. IA values decreased less significantly (12, 14 and 15% for Liaison, iSYS and Vidas, respectively). IA-based calculated free 25OH-D significantly increased after dilution, while LC-MS/MS-based free values remained stable. At T1 and T2, bias were demonstrable for all IA. After hemodilution, bias would lead to overestimation for the three IA. Accuracy of IA decreased after dilution., Conclusions: Due to matrix effects, compared to LC-MS/MS, IA results were impacted by hemodilution. In CC patients, LC-MS/MS seems to be the best option to measure 25OH-D. Specific LC-MS/MS method should be developed to measure free 25OH-D., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Introduction: Standardization of immunoassays for 25(OH)-vitamin D determination is a major problem in clinical practice. A worldwide standardization program has started to address this and will reduce the bias observed between immunoassays. We aimed to calibrate 5 immunoassays on a LC-MS/MS traceable to the SRM 2972 and the ID-LC-MS/MS 25(OH)D Reference Method Procedure to see if the re-standardization would be efficient in a population of 3rd trimester pregnant women (PW), hemodialysis (HD) and osteoporosis (OP) patient., Material and Methods: 184 serum samples (25(OH)D: 8.4-87 ng/ml) were selected to calibrate the immunoassays (Abbott-Architect, Roche-Elecsys, DiaSorin-Liaison, Siemens-Centaur and IDS-iSYS). Chromsystems MassChrom method was used as the referenced. Serum obtained in 34 PW, 25 HD and 34 OP patients were used as comparatives., Results: After adjusting to LC-MS/MS, immunoassays had regression slopes nearly identical to 1.0 with intercepts <0.5 ng/ml. However, in special populations, a systematic bias was still observed, except for iSYS., Conclusions: Re-standardization of 25(OH)D immunoassay will globally improve the differences. However, patients with a different serum matrix will still present significantly different results when they will be run with different methods. For those patients, the LC-MS/MS method seems to be the method of choice, even if some immunoassays are less influenced than others., (Copyright © 2014 Elsevier B.V. All rights reserved.)

The National Kidney Disease Education Program group demonstrated that MDRD equation is sensitive to creatinine measurement error, particularly at higher glomerular filtration rates. Thus, MDRD-based eGFR above 60 mL/min/1.73 m² should not be reported numerically. However, little is known about the impact of analytical error on CKD-EPI-based estimates. This study aimed at assessing the impact of analytical characteristics (bias and imprecision) of 12 enzymatic and 4 compensated Jaffe previously characterized creatinine assays on MDRD and CKD-EPI eGFR. In a simulation study, the impact of analytical error was assessed on a hospital population of 24084 patients. Ability using each assay to correctly classify patients according to chronic kidney disease (CKD) stages was evaluated. For eGFR between 60 and 90 mL/min/1.73 m², both equations were sensitive to analytical error. Compensated Jaffe assays displayed high bias in this range and led to poorer sensitivity/specificity for classification according to CKD stages than enzymatic assays. As compared to MDRD equation, CKD-EPI equation decreases impact of analytical error in creatinine measurement above 90 mL/min/1.73 m². Compensated Jaffe creatinine assays lead to important errors in eGFR and should be avoided. Accurate enzymatic assays allow estimation of eGFR until 90 mL/min/1.73 m² with MDRD and 120 mL/min/1.73 m² with CKD-EPI equation., (Copyright © 2013 Elsevier B.V. All rights reserved.)

The French Society of Clinical Biochemistry conducted this study to compare the accuracy and performances of the best creatinine enzymatic assays and the compensated Jaffe methods from the same manufacturers. Creatinine was measured in 3 serum pools with creatinine levels of 35.9±0.9 μmol/L, 74.4±1.4 μmol/L, and 97.9±1.7 μmol/L (IDMS determination). The performances of the assays (total error that includes the contribution of bias and imprecision) were evaluated using Monte-Carlo simulations and compared against desirable NKDEP criteria. The enzymatic assays always fell within the desirable total Error of 7.6%. By contrast, this requirement was never obtained for the compensated Jaffe methods at the critical level of 74.4±1.4 μmol/L. Only the compensated Jaffe creatinine on Olympus analyzer reached this specification at 35.9±0.9 and 97.9±1.7 μmol/L levels. This study demonstrates that, despite substantial improvement regarding traceability to the IDMS reference method and precision, compensated Jaffe creatinine methods, by contrast to enzymatic ones, do not reach the desirable specifications of NKDEP at normal levels of creatinine., (Copyright © 2013 Elsevier B.V. All rights reserved.)

Background: Chronic Kidney Disease (CKD) is associated with mineral and bone disorders (MBD). International guidelines suggest that levels of serum parathormone (PTH) or bone-specific alkaline phosphatase (b-ALP) can be used to evaluate MBD in dialysis patients. The evidence remains moderate and based on transversal studies., Methods: We retrospectively investigated the variations of PTH (ΔPTH) and b-ALP (Δb-ALP) serum concentrations over a short (6-weeks) and a long (one-year) period in a monocentric hemodialysis population. The proportion of patients reaching the critical difference (CD) (50% for PTH and 25% for b-ALP) was calculated., Results: Seventy-seven patients were included. A significant correlation between PTH and b-ALP levels was found at baseline (r=0.51). By contrast, no correlation was observed between ΔPTH and Δb-ALP over a 6-week interval (r=0.07). The CD for PTH and b-ALP was reached by 19 and 11 patients, respectively, with 2 patients showing consistent variations of both biomarkers. One year later, measurements were repeated in 48 survivors. No correlation was found between ΔPTH and Δb-ALP (r=0.27). The CD for PTH or b-ALP was reached by 24 patients and 28 patients, respectively, with 6 patients (12.5%) showing opposite results for both biomarkers., Conclusion: This study shows the lack of correlation between ΔPTH and Δb-ALP over time in patients under chronic hemodialysis., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: The recent evaluation of the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for estimating the glomerular filtration rate (GFR) in multiple ethnicities has raised the question on how well this equation performs for African-American and Asian subjects. There is no doubt that serum creatinine (Scr) concentration differs between ethnicities and sexes. We show that creatinine-based equations for white populations may be inaccurate for estimating GFR in other ethnic/gender groups, especially in populations from Asia., Methods: This study presents a mathematical analysis of the CKD-EPI-equation complemented with a literature review of median and reference values for IDMS-standardized Scr-concentrations for multiple ethnicities., Results: The study shows that at equal eGFR-CKD-EPI-values, the ratio of Scr between females and males equals 0.79 and between other ethnicities/sexes and white males is constant too. From this information, it is possible to calculate mean Scr-values that correspond very well with literature values directly obtained from Scr-distributions in healthy white males and females and in black males, but the discrepancy is larger for other populations., Conclusions: Our results confirm the criticism that has been raised for using the CKD-EPI-equation for these ethnicities. An alternative eGFR-model is proposed based on a population-normalized Scr that needs further validation., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Among issues susceptible to hamper a reliable measurement of inulin clearance, those regarding the dosage of inulin are largely neglected. We have compared the analytical performances of 2 commonly used methods of inulin dosage (one "acid" and one "enzymatic" method) and studied their potential impact on the glomerular filtration rate (GFR) value given by inulin clearance. Repeatability, uncertainty and the beta-expectation limits were evaluated from pre-determined serum and urine pools of inulin. Agreement between the two methods was analyzed from 99 inulin clearances performed in renal transplant patients. Impact of the method of dosage on GFR evaluation was simulated according to the respective beta-expectations limits of each method. Overall, intra-assay coefficient of variability and relative bias were inferior to 5% and 10% for both methods. Contrary to the acid method, analytical performance of the enzymatic method was not influenced by the presence of glucose. The relative difference in GFR values obtained with the two methods in transplant patients was -0.4 ± 10%. Simulations suggested that changes in inulin concentration attributable to analytical error could modify the value of GFR from -12% to +28%. In conclusion, while analytical performances are globally acceptable for both methods, they are not strictly equivalent. The impact on the determination of GFR, albeit limited, is not negligible and adds to other sources of inaccuracy. International standardization for the dosage of inulin is necessary., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Chronic kidney disease definition is based on glomerular filtration rate (GFR) estimations which are derived from creatinine-based equations. The accuracy of GFR estimation is thus largely dependent of those of serum creatinine assays. International recommendations highlight the need for traceable creatinine assays. The French Society of Clinical Biochemistry conducted a study for measuring accuracy of creatinine enzymatic methods. This evaluation involved 25 clinical laboratories. Creatinine was measured in serum pools ranging from 35.9±0.9 μmol/L to 174.5±3.1 μmol/L (IDMS determination) using 12 creatinine enzymatic methods. For all creatinine values greater than 74.4±1.4 μmol/L, the bias and imprecision did not exceed 5% and 5.9%, respectively. For the lowest value (35.9±0.9 μmol/L), the bias ranged from -1.8 to 9.9% (with one exception). At this level, the imprecision ranged from 1.9 to 7.8%. The true performances of the assays (couples of bias and relative standard deviation), were evaluated using Monte-Carlo simulations. Most of the assays fall within the maximum Total Error of 12% at all concentrations. This study demonstrates substantial improvements in the calibration, traceability and precision of the enzymatic methods, reaching the NKDEP recommendations. Moreover, most of these assays allowed accurate creatinine measurements for creatinine levels lower than 40 μmol/L., (Copyright © 2011 Elsevier B.V. All rights reserved.)