Comparison of the Schwartz and CKD-EPI Equations for Estimating Glomerular Filtration Rate in Children, Adolescents, and Adults: A Retrospective Cross-Sectional Study

Development and validation of a new equation to estimate glomerular filtration rate in Argentinian adults

Latin Americans are underrepresented in the current equations used to estimate glomerular filtration rate (GFR), and the applicability of their predictions to this population may therefore be questionable. The objective of this study was to develop a new equation to estimate GFR based on data from Argentina. A cross-sectional study was conducted. We included 583 Argentinian adults in development sample (DS) and 78 in temporary validation sample (TVS). Urinary iothalamate clearance (reference method), and different predictive variables were used to develop candidate equations to estimate GFR. The performance was assessed through 10-fold cross-validation in DS, and by direct validation in TVS, using root mean squared error (RMSE), correlation (r), bias, P15, P30 and correct classification percentage (CC%) in CKD stages. The Argentinian equation (AE) chosen is based on a quasi-likelihood model which predicts GFR from creatinine, age, sex, single kidney, albumin and urea. Within the previous creatinine based equations (MDRD, MCQ, CKD-EPI and EKFC), the ones with the best performance were CKD-EPI 2009 and 2021. In the DS, AE showed lower RMSE, similar r, higher P15, median bias closer to zero and higher CC% compared to CKD-EPI 2009, and very slight differences in comparison to CKD-EPI 2021. In the TVS, AE presented lower RMSE, higher (or equal) r, P30 and CC%, and median bias closer to 0 compared to CKD-EPI in its two versions. In addition, it presented higher P15 than CKD-EPI 2009. In conclusion, AE presented a better performance to estimate GFR in Argentinian people and its use could have a positive impact on the clinical management of these patients.

Switching to the CKD-EPI but Not Modified FAS eGFR Formula Underdetects CKD Among Adolescents and Young Adults in México

BACKGROUND

Guidelines recommend switching the glomerular filtration rate (eGFR) estimation from the CKiD-U25 to the CKD-EPI formula at age 18. We investigated how this would affect chronic kidney disease (CKD) classification.

METHODS

Serum creatinine was enzymatically measured in 1061 samples from 914 community-based 10-23-year-olds from Tlaxcala, Mexico, a region where urinary biomarkers demonstrated early kidney damage associated with exposure to inorganic toxins in a pediatric population. We calculated their eGFR using CKiD-U25, modified Schwartz, the first and modified Pottel full-age spectrum (FAS), and CKD-EPI formulae. Correlation analysis characterized the CKD stage stratified by age and sex.

RESULTS

At baseline, the median age was 13 (IQR: 12, 15) years, and 55% were female. Median CKiD-U25 eGFR was 96.9 (IQR: 83.3, 113.3) mL/min/1.73 m2, significantly lower than the CKD-EPI eGFR, which was 140.8 (IQR: 129.9, 149.3) mL/min/1.73 m2 (p < 0.0001, Wilcoxon rank test). The mean bias was 36.99 ± 12.89 mL/min/1.73 m2. Pearson correlation was r = 0.8296 (95% confidence interval 0.0898-0.8474). There was a better correlation between the modified Schwartz (r = 0.9421 (0.9349, 0.9485)) and the Pottel FAS (r = 0.9299 (0.9212, 0.9376)) formulae. Agreement was deficient when the eGFR was >75 mL/min/1.73 m2 in younger age and female sex. Modified Schwartz identified 281 (26.4%) measurements as having CKD 2 and 3 (2+), U25 identified 401 (37.7%) measurements as having CKD 2+, FAS identified 267 (25.1%) and modified FAS identified 282 (30%) measurements as having CKD 2+, and CKD-EPI identified 51 (4.8%) measurements as having CKD 2+, respectively.

CONCLUSIONS

In this population, there needed to be better agreement between the various eGFR formulae. CKD-EPI identifies substantially fewer at-risk participants as having CKD.

Associations of resuscitation fluid load, colloid-to-crystalloid infusion ratio and clinical outcomes in children with dengue shock syndrome

BACKGROUND

Severe respiratory distress and acute kidney injury (AKI) are key factors leading to poor outcomes in patients with dengue shock syndrome (DSS). There is still limited data on how much resuscitated fluid and the specific ratios of intravenous fluid types contribute to the development of severe respiratory distress necessitating mechanical ventilation (MV) and AKI in children with DSS.

METHODOLOGY/PRINCIPAL FINDINGS

This retrospective study was conducted at a tertiary pediatric hospital in Vietnam between 2013 and 2022. The primary outcomes were the need for MV and renal function within 48 h post-admission. A predictive model for MV was developed based on covariates from the first 24 h of PICU admission. Changes in renal function within 48 h were analyzed using a linear mixed-effects model. A total of 1,278 DSS children with complete clinical and fluid data were included. The predictive performance of MV based on the total intravenous fluid volume administered yielded an AUC of 0.871 (95% CI, 0.836-0.905), while the colloid-to-crystalloid ratio showed an AUC of 0.781 (95% CI, 0.743-0.819) (both P < 0.001). The optimal cut-off point of the cumulative fluid infusion was 181 mL/kg, whereas that of the colloid-to-crystalloid ratio was 1.6. Multivariable analysis identified female patients, severe bleeding, severe transaminitis, excessive fluid resuscitation, and a higher proportion of colloid solutions in the first 24 h as significant predictors of MV in DSS patients. The predictive model for MV demonstrated high accuracy, with a C-statistic of 89%, strong calibration, and low Brier score (0.04). Importantly, a more pronounced decline in glomerular filtration rate was observed in DSS patients who required MV than in those who did not.

CONCLUSIONS/SIGNIFICANCE

This study provides insights into optimizing fluid management protocols, highlighting the importance of monitoring fluid volume and the colloid-to-crystalloid ratio during early resuscitation to improve the clinical outcomes of DSS patients.

Comorbidities associated with chronic kidney disease among young people living with HIV in Uganda. A nested case control study

Introduction

Chronic kidney disease (CKD) is often complicated by disorders in multiple body systems, associated with higher mortality and morbidity. Young people living with HIV (YPLHIV) have an increased risk of multisystem chronic comorbidities. However, there are few data describing comorbidities associated with CKD among YPLHIV.

Methods

We conducted a case-control study in seven ART clinics in Kampala, Uganda. Cases were YPLHIV (aged 10-24 years) diagnosed with CKD and controls were those without CKD. We collected data on demographic and clinical factors: blood pressure, fasting glucose levels, anaemia, electrolytes, parathyroid hormone, and cognitive impairment. We summarized the demographic and clinical factors and used logistic regression to estimate odds ratios (OR) and 95% confidence intervals for associations between CKD comorbidities, adjusted for age, sex and viral suppression.

Results

A total of 292 participants (96 cases and 196 controls) were recruited. Cases were mostly male (59.4% vs 36.5%), and younger (88.5% vs 46.4% aged <17 years) compared to controls. CKD was associated with having a detectable HIV viral load (OR=3.73; 95% CI 1.53-9.12) and proteinuria (aOR=4.19; 95% CI 2.28-7.72). CKD was also associated with low haematocrit, hypochloraemia, hyperphosphatemia, and high mean corpuscular volume. There was no evidence of an association of CKD with hypertension, anaemia, or stunting.

Conclusion

The pattern of comorbidities among YPLHIV with CKD is uncertain and difficulties may relate to difficulty determining true kidney function and normal ranges in this population. Further studies are needed to discern the pattern of CKD complications to improve management efforts and clinical outcomes.

Creatinine-based formulas are not ideal to estimate glomerular filtration rate in selected pediatric patients: data from a tertiary pediatric nephrology center

BACKGROUND

Evaluating glomerular filtration rate (GFR) remains challenging in pediatrics; new formulas were developed to increase performance of GFR estimation (eGFR). We aimed to evaluate the recently published formulas as applied to another pediatric population.

METHODS

A retrospective study was conducted in a cohort of 307 patients with a "kidney risk" (mean age 12.1 ± 4.5 years, sex ratio 1/1) assessed in a tertiary pediatric nephrology center and a mean measured GFR (mGFR) using plasma iohexol clearance of 85.5 ± 25.3 mL/min/1.73 m2; creatinine levels were measured by IDMS-standardized enzymatic method and cystatin C by immunonephelometry. The following eGFRs were calculated: Schwartz2009, Schwartz-Lyon, CKiDU25creat, and EKFC for eGFR using creatinine (eGFR-creat), CKiDU25cys and FAScys for eGFR using cystatin (eGFR-cys) as well as combined SchwartzCreat-Cys, average (CKiDU25creat-CKiDU25cys), and average (EKFC-FAScys) for eGFR using both biomarkers. The performance of the different formulas was evaluated compared to mGFR by absolute bias measurement and accuracy (p10%, p30%). Results are expressed as mean ± SD.

RESULTS

Creatinine-based formulas and especially the new CKiDU25 and EKFC overestimate GFR, even in children with normal kidney function. However, the bias is constant with these two formulas whatever the age group or gender, contrary to the previously published formulas. In contrast, cystatin C-based equations and combined formulas showed good performance in all age groups and all medical conditions with an acceptable bias and p30%.

CONCLUSIONS

In our pediatric population, the performance of all creatinine-based formulas is inadequate with significant GFR overestimation, mainly in subjects with mGFR > 75 mL/min/1.73 m2. Conversely, cystatin C-based or combined formulas have acceptable performance in patients followed in a tertiary pediatric nephrology unit.

Evaluation of the clinical value of 10 estimating glomerular filtration rate equations and construction of a prediction model for kidney damage in adults from central China

Objectives

This study aimed to evaluate 10 estimating glomerular filtration rate (eGFR) equations in central China population and construct a diagnostic prediction model for assessing the kidney damage severity.

Methods

The concordance of 10 eGFR equations was investigated in healthy individuals from central China, and their clinical effectiveness in diagnosing kidney injury was evaluated. Subsequently, relevant clinical indicators were selected to develop a clinical prediction model for kidney damage.

Results

The overall concordance between CKD-EPIASR-Scr and CKD-EPI2021-Scr was the highest (weightedκ = 0.964) in healthy population. The CG formula, CKD-EPIASR-Scr and CKD-EPI2021-Scr performed better than others in terms of concordance with referenced GFR (rGFR), but had poor ability to distinguish between rGFR < 90 or < 60 mL/min·1.73 m2. This finding was basically consistent across subgroups. Finally, two logistic regression prediction models were constructed based on rGFR < 90 or 60 mL/min·1.73 m2. The area under the curve of receiver operating characteristic values of two prediction models were 0.811 vs 0.846 in training set and 0.812 vs 0.800 in testing set.

Conclusion

The concordance of CKD-EPIASR-Scr and CKD-EPI2021-Scr was the highest in the central China population. The Cockcroft-Gault formula, CKD-EPIASR-Scr, and CKD-EPI2021-Scr more accurately reflected true kidney function, while performed poorly in the staging diagnosis of CKD. The diagnostic prediction models showed the good clinical application performance in identifying mild or moderate kidney injury. These findings lay a solid foundation for future research on renal function assessment and predictive equations.

Meropenem Disposition in Neonatal and Pediatric Extracorporeal Membrane Oxygenation and Continuous Renal Replacement Therapy

This study aimed to characterize the impact of extracorporeal membrane oxygenation (ECMO) on the pharmacokinetics (PK) of meropenem in neonates and children and to provide recommendations for meropenem dosing in this specific population of patients. Therapeutic drug monitoring (152 meropenem plasma concentrations) data from 45 patients (38 received ECMO) with a body weight (BW) of 7.88 (3.62-11.97) kg (median (interquartile range)) and postnatal age of 3 (0-465) days were collected. The population PK analysis was performed using NONMEM V7.3.0. Monte Carlo simulations were performed to assess the probability of target achievement (PTA) for 40% of time the free drug remained above the minimum inhibitory concentration (fT > MIC) and 100% fT > MIC. BW was found to be a significant covariate for the volume of distribution (Vd) and clearance (CL). Additionally, continuous renal replacement therapy (CRRT) was associated with a two-fold increase in Vd. In the final model, the CL and Vd for a typical patient with a median BW of 7.88 kg that was off CRRT were 1.09 L/h (RSE = 8%) and 3.98 L (14%), respectively. ECMO did not affect meropenem PK, while superimposed CRRT significantly increased Vd. We concluded that current dosing regimens provide acceptably high PTA for MIC ≤ 4 mg/L for 40% fT > MIC, but individual dose adjustments are needed for 100% fT > MIC.

Limitations of U25 CKiD and CKD-EPI eGFR formulae in patients 2-20 years of age with measured GFR > 60 mL/min/1.73 m2-a cross-sectional study

BACKGROUND

When applying Pierce U25 formula for estimating glomerular filtration rate (eGFR), we observed a higher proportion of eGFR < 90 mL/min/1.73 m2 (chronic kidney disease (CKD) stage 2). We compared agreement and accuracy of the Pierce U25 (ages 2-25), Pottel (ages 2-100), and CKD-EPI (ages 18-100) formulae to GFR measurements.

METHODS

Post hoc analysis of the three eGFRs compared to 367 99m technetium-diethylene-triamine penta-acetic acid (99Tc DTPA) GFR measurements (240 patients) using 3 sampling points and Brockner/Mørtensen correction (body surface area calculation based on ideal weight) on simultaneous serum creatinine and cystatin C measurements.

RESULTS

Overall, the U25 formula performed well with a Spearman r of 0.8102 (95% confidence interval 0.7706 to 0.8435, p < 0.0001) while diagnostic accuracy was low in patients with normal mGFR. The U25 formula reclassified 29.5% of patients with normal mGFR as CKD stage 2; whereas the average of the modified Schwartz formula based on serum creatinine and the Filler formula based on cystatin C, only over-diagnosed CKD stage 2 in 8.5%, 24.5% within 10% and 62.7% within 30%. We therefore combined both. The average Schwartz/Filler eGFR had 36.5% of results within 10%, 84.7% within 30%, and normal mGFR accuracy was 26.8%, 63.9% for 10% and 30%, respectively, outperforming the CKD-EPI and Pottel formulae.

CONCLUSIONS

The Pierce U25 formula results correlated well with mGFR < 75 mL/min/1.73 m2. Over the entire GFR range, accuracy was better for patients with a higher mGFR, when averaging the combined Schwartz/Filler formulae. More work is needed to prospectively confirm our findings in other centers.

Creatinine-based European Kidney Function Consortium equation is superior to the Chronic Kidney Disease Epidemiology Collaboration equation for mortality risk stratification in general non-Black population

AIMS

A recent study demonstrated that the new modified estimated glomerular filtration rate (eGFR) equation proposed by the European Kidney Function Consortium (EKFC) was more accurate and precise than the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation. This study aimed to compare the prognostic values of these two creatinine-based equations with regard to all-cause and cardiovascular mortality in general non-Black population.

METHODS AND RESULTS

A population-based cohort study was conducted using data from the National Health and Nutrition Examination Survey database from 1999 to 2018, and 38 983 non-Black individuals aged 20 years or older without a history of dialysis were enrolled. Among 38 983 participants, 6103 deaths occurred after a median follow-up duration of 112 months, of which 1558 deaths were due to cardiovascular causes. There were U-shaped relations between the eGFR values and the risk of all-cause and cardiovascular mortality. The areas under the curves for the EKFC were significantly higher than those for the CKD-EPI equation for all-cause and cardiovascular mortality. The integrated discrimination improvement for the EKFC equation compared with the CKD-EPI equation was 2.40% and 1.26% for 10-year all-cause and cardiovascular mortality; the net reclassification improvement for the EKFC equation compared with the CKD-EPI equation was 8.67% and 11.13% for 10-year all-cause mortality and cardiovascular mortality.

CONCLUSION

Creatinine-based EKFC equation outperformed the CKD-EPI equation for the prediction of long-term all-cause and cardiovascular mortality in the general non-Black population.

Changes in Kidney Function Among Malaysian Adolescents and Its Determinants

Introduction

The health and wellbeing of adolescents are often neglected, including the knowledge of chronic kidney disease (CKD), especially in its early stages.

Methods

A total of 607 adolescents were recruited from the Malaysian Health and Adolescents Longitudinal Research Team (MyHeART) study, a prospective cohort study conducted from March 2012 to May 2016 that explored the noncommunicable diseases (NCDs) risk factors among 13 to 17 years old students in 3 states of Peninsular Malaysia. Students who participated in all 3 data collection periods in 2012, 2014, and 2016 with kidney function assessment across all 3-time points were included in the current study. The students' estimated glomerular filtration rate (eGFR) was calculated from isotope-dilution mass spectrometry-traceable Schwartz's equation and categorized based on Kidney Disease: Improving Global Outcomes (KDIGO) classification. Changes in kidney function were examined, and the longitudinal relationship between eGFR and multiple NCD risk factors was analyzed using the generalized estimating equation (GEE).

Results

The prevalence of decreased eGFR (60-89 ml/min per 1.73 m2) among the students increased from 6.1% (2012) to 30.0% (2014) and 40.2% (2016). Based on the GEE, the student's eGFR decreased over time, with a steeper decline during early to midadolescence. Males and rural students had lower eGFR compared to their counterparts. Students who are morbidly obese had lower eGFR than those with normal body mass index (BMI). Protein consumption also has a potential moderating effect on eGFR in adolescents.

Conclusion

Kidney function changes can be detected as early as adolescence and are likely attributable to multiple NCD risk factors. Therefore, more comprehensive prevention efforts from various stakeholders are needed to identify health issues like CKD.

New and old GFR equations: a European perspective

Glomerular filtration rate (GFR) is estimated in clinical practice from equations based on the serum concentration of endogenous biomarkers and demographic data. The 2009 creatinine-based Chronic Kidney Disease Epidemiology Collaboration equation (CKD-EPI2009) was recommended worldwide until 2021, when it was recalibrated to remove the African-American race factor. The CKD-EPI2009 and CKD-EPIcr2021 equations overestimate GFR of adults aged 18-30 years, with a strong overestimation in estimated GFR (eGFR) at age 18 years. CKD-EPICr2021 does not perform better than CKD-EPI2009 in US population, overestimating GFR in non-Black subjects, and underestimating it in Black subjects with the same magnitude. CKD-EPICr2021 performed worse than the CKD-EPI2009 in White Europeans, and provides no or limited performance gains in Black European and Black African populations. The European Kidney Function Consortium (EKFC) equation, which incorporates median normal value of serum creatinine in healthy population, overcomes the limitations of the CKD-EPI equations: it provides a continuity of eGFR at the transition between pediatric and adult care, and performs reasonably well in diverse populations, assuming dedicated scaling of serum creatinine (Q) values is used. The new EKFC equation based on cystatin C (EKFCCC) shares the same mathematical construction, namely, it incorporates the median cystatin C value in the general population, which is independent of sex and ethnicity. EKFCCC is therefore a sex-free and race-free equation, which performs better than the CKD-EPI equation based on cystatin C. Despite advances in the field of GFR estimation, no equation is perfectly accurate, and GFR measurement by exogenous tracer clearance is still required in specific populations and/or specific clinical situations.

Meta-Analysis on Long-Term Outcomes of Pediatric Renal Cancer Survivors Following COG and SIOP Protocols

BACKGROUND

 Pediatric renal cancer survivors have higher rate of chronic renal disease and hypertension. These patients have similar survival rates when treated according to either Children's Oncology Group (COG) or International Society of Pediatric Oncology (SIOP) protocols. We aimed to compare the late outcome of these two approaches.

METHODS

 We performed a meta-analysis of all studies from 2000 to 2021; database search using keywords: long-term outcomes OR late effects, nephrectomy, pediatric renal cancer. For each protocol, data were collected, and the "pooled" outcomes were compared. Continuous and dichotomous variables were obtained with a 95% odds ratio.

RESULTS

 Sixteen studies with a total of 715 pediatric renal cancer survivors were analyzed. The mean follow-up time was 17.4 (standard deviation 5.6) years. Reduced renal function and hypertension were the most encountered long-term complications. The mean estimated glomerular filtration rate was similar in both protocols (101.62 vs. 101.70 mL/min/1.73 m2), while the prevalence of hypertension was 23% in COG and 10% in SIOP. The prevalence of secondary malignancy was 1.1% in COG and 6.7% in SIOP (1.1% vs. 6.7%, p ≤ 0.001). Chronic kidney disease was similar in both groups.

CONCLUSION

 A high prevalence of hypertension was observed among pediatric renal cancer survivors, as well as an increased risk of a secondary tumor. These results emphasize the importance of long-term follow-up into adulthood, to promptly diagnose any long-term side effects of the treatment. Thanks to the increased overall survival, future protocols will pay attention to the reduction of long-term sequelae.

Clinical outcomes among young patients with Fabry disease who initiated agalsidase beta treatment before 30 years of age: An analysis from the Fabry Registry

BACKGROUND

Clinical manifestations of classic Fabry disease (α-galactosidase A deficiency) usually occur in childhood, while complications involving major organs typically develop in adulthood. Outcomes of Fabry-specific treatment among young patients have not been extensively reported. Our aim was to analyze clinical outcomes among patients aged 5-30 years at initiation of treatment with agalsidase beta using data from the Fabry Registry (NCT00196742, sponsor: Sanofi).

METHODS

Reported GLA variants were predicted to be associated with the classic phenotype or not classified in fabry-database.org. Linear mixed models were conducted to assess changes over ≥2-year follow-up in the estimated glomerular filtration rate (eGFR) stratified by low (LRI) and high (HRI) renal involvement (defined by proteinuria/albuminuria levels), and changes in interventricular septal thickness (IVST) and left ventricular posterior wall thickness (LVPWT) Z-scores stratified by median age at first treatment. Self-reports ('yes'/'no') of abdominal pain, diarrhea, chronic peripheral pain (denoting neuropathic pain), and acute pain crises at baseline were compared with reports after ≥0.5-year and ≥2.5-year follow-up using McNemar's test.

RESULTS

Male (n = 117) and female patients (n = 59) with LRI initiated treatment at a median age of 19.9 and 23.6 years, respectively, and were followed for a median of 6.3 and 5.0 years, respectively. The eGFR slopes were -1.18 (P_{from 0} <0.001) and -0.92 mL/min/1.73 m²/year (P_{from 0} = 0.040), respectively. Males with HRI (n = 23, median UPCR 1.0 g/g), who started treatment at a median age of 26.7 years, had an eGFR slope of -2.39 mL/min/1.73 m²/year (P_{from 0} <0.001; P_difference = 0.055, as compared with the slope of -1.18 mL/min/1.73 m²/year for LRI males) during a median follow-up of 5.6 years. Echocardiographic variables were stable among males, regardless of age, and among young females (median follow-up >5.5 years and ≥4.5 years, respectively). Older females (treatment initiation at median age 27.5 years) had a slope of LVPWT Z-scores of 0.18/year (n = 12, P_{from 0} = 0.028), whereas IVST Z-scores remained stable (n = 13, 0.10/year, P_{from 0} = 0.304) during a median follow-up of ≥3.7 years. These slopes did not significantly differ from slopes of younger females. Reports of chronic peripheral pain and acute pain crises by males, and of diarrhea and acute pain crises by females, significantly reduced after a median follow-up of ≥4.0 years. After a median follow-up of ≥5.4 years, reports of all four symptoms significantly decreased among males, whereas among females only reports of abdominal pain significantly decreased.

CONCLUSIONS

During sustained treatment with agalsidase beta in young Fabry patients with a predicted classic phenotype or with unclassified GLA variants with similar characteristics, the decline in eGFR was modest among male and female patients with LRI. The greater decline in eGFR among older, proteinuric (i.e., HRI) males may suggest a benefit of earlier treatment. Overall, echocardiographic variables remained stable, particularly among males and younger females. Significant reductions in symptom reports occurred primarily among males after longer follow-up and were less noticeable among females. These observed trends are suggestive of an overall improvement after treatment in young patients, but warrant larger longitudinal studies.

Performance of creatinine-based equations to estimate glomerular filtration rate in White and Black populations in Europe, Brazil and Africa

BACKGROUND

A new Chronic Kidney Disease Epidemiology Collaboration equation without the race variable has been recently proposed (CKD-EPIAS). This equation has neither been validated outside USA nor compared with the new European Kidney Function Consortium (EKFC) and Lund-Malmö Revised (LMREV) equations, developed in European cohorts.

METHODS

Standardized creatinine and measured glomerular filtration rate (GFR) from the European EKFC cohorts (n = 13 856 including 6031 individuals in the external validation cohort), from France (n = 4429, including 964 Black Europeans), from Brazil (n = 100) and from Africa (n = 508) were used to test the performances of the equations. A matched analysis between White Europeans and Black Africans or Black Europeans was performed.

RESULTS

In White Europeans (n = 9496), both the EKFC and LMREV equations outperformed CKD-EPIAS (bias of -0.6 and -3.2, respectively versus 5.0 mL/min/1.73 m², and accuracy within 30% of 86.9 and 87.4, respectively, versus 80.9%). In Black Europeans and Black Africans, the best performance was observed with the EKFC equation using a specific Q-value (= concentration of serum creatinine in healthy males and females). These results were confirmed in matched analyses, which showed that serum creatinine concentrations were different in White Europeans, Black Europeans and Black Africans for the same measured GFR, age, sex and body mass index. Creatinine differences were more relevant in males.

CONCLUSION

In a European and African cohort, the performances of CKD-EPIAS remain suboptimal. The EKFC equation, using usual or dedicated population-specific Q-values, presents the best performance in the whole age range in the European and African populations included in this study.

Clinicopathologic Manifestations of Immunoglobulin A Nephropathy in a Northern Indian Cohort: A Mute Assassin with Delayed Diagnosis

Introduction

Immunoglobulin A nephropathy (IgAN) is the most common glomerulonephritis worldwide, but there is a marked geographic difference in its prevalence and prognosis. IgAN is known to have an aggressive course in Asians. However, its exact prevalence and clinicopathologic spectrum in North India are not well documented.

Materials and Methods

The study included all patients aged above 12 years with primary IgAN on kidney biopsy from January 2007 to December 2018. Clinical and pathological parameters were noted. Two histopathologists independently reviewed all kidney biopsies, and MEST-C score was assigned as per the Oxford classification.

Results

IgAN was diagnosed in 681 (11.85%) out of 5751 native kidney biopsies. The mean age was 32 ± 12.3 years, and the male to female ratio was 2.5:1. At presentation, 69.8% had hypertension, 68% had an estimated glomerular filtration rate (eGFR) of less than 60 ml/min, 63.2% had microscopic hematuria, and 4.6% had gross hematuria. The mean proteinuria was 3.61 ± 2.26 g/day, with 46.8% showing nephrotic range proteinuria and 15.2% showing nephrotic syndrome manifestation. Histopathologically, 34.4% of patients had diffuse global glomerulosclerosis. Oxford MEST-C scoring revealed M1 in 67%, E1 in 23.9%, S1 in 46.9%, T1/T2 in 33%, and crescents in 19.6% of biopsies. The mean serum creatinine was significantly higher in cases with E1, T1/2, and C1/2 scores (P < 0.05). Hematuria and proteinuria were significantly higher (P < 0.05) with E1 and C1/2 scores. Coexisting C3 was associated with higher serum creatinine at presentation (P < 0.05).

Conclusion

IgAN patients with late presentation and advanced disease became less amenable to immunomodulation in our cohort. The implementation of point-of-care screening strategies, early diagnosis, and retarding disease progression should be prioritized in the Indian strategy.

Long-Term Survival and Kidney Function in Pediatric Patients Following Liver Transplantation: A 15-Year Retrospective Cohort Study

Long-term preservation of kidney function after liver transplantation (LT) has not been well studied. We thus evaluated the rates of kidney function preservation and long-term survival after pediatric LT. We also investigated the risk factors associated with the progression of chronic kidney disease (CKD). We conducted a retrospective study of 184 pediatric patients who had undergone LT from 2003 to 2018 at a university hospital. We collected demographics, primary indications for LT, liver disease scores, renal function test results, immunosuppressive drug prescriptions, and diagnosis of post-LT complications. The 15-year survival rate was 90.8%. Furthermore, the rate of kidney function preservation at 14 years post-LT in patients at high risk of renal disease was 79.3%, and that in those with less risk of kidney diseases was 96.0%. Arterial hypertension was an independent risk factor associated with CKD progression. However, when arterial hypertension was excluded, the use of cyclosporine and liver disease with renal involvement were risk factors for CKD progression. We found that kidney function after pediatric LT was well preserved. We encourage the early detection of underlying kidney involvement, routine monitoring of renal function for high-risk patients, active control of hypertension, and appropriate immunosuppressive regimens for pediatric patients with LT.

Prospective Evaluation of Kidney Function in Long-Term Survivors of Pediatric CNS Tumors

Purpose: Numerous acute effects of chemotherapeutics on kidney function are well described. However, data on the long-term effects of chemotherapy in the growing population of childhood central nervous system (CNS) tumor survivors is limited. We aimed to evaluate the kidney function of a cohort of long-term CNS tumor survivors treated with different standard chemotherapeutic regimens. Methods: Patients treated for a CNS tumor were prospectively evaluated up to 12 years after completion of their therapy. Examination of kidney function was performed during routine follow-up visits. Blood pressure and blood and urine parameters were analyzed for kidney function evaluation. Glomerular function was assessed by calculating the estimated glomerular filtration rate (eGFR), tubular functions were analyzed by measuring serum electrolytes, bicarbonate and phosphate reabsorption, and proteinuria was assessed by calculating the protein/creatinine ratio and phosphate reabsorption. Results: None of the 65 patients evaluated suffered from clinically relevant kidney impairment (eGFR < 90 mL/min/L, 73 m2). There was no association between chemotherapy dose and eGFR. Only two patients showed mild signs of tubulopathy and 11 patients were diagnosed with elevated blood pressure. Conclusion: With adequate supportive measures, such as sufficient hydration according to chemotherapy protocol guidelines, as well as avoidance or close monitoring of additional nephrotoxic medication, impaired kidney function is rare in CNS tumor survivors treated with standard chemotherapy. Nonetheless, long-term follow-up is essential for early detection of mild impairment of kidney function.

Teenagers and young adults with a past of allogenic hematopoietic stem cell transplantation are at significant risk of chronic kidney disease

BACKGROUND

Allogenic hematopoietic stem cell transplantation (aHSCT) remains the treatment of choice for some malignant hemopathies in children, albeit with the risk of long-term consequences, including chronic kidney disease (CKD).

METHODS

In our single tertiary referral center, we retrospectively assessed the long-term renal outcome in a cohort of children and adolescents who had undergone aHSCT for malignant hemopathies between 2003 and 2017. We distinguished glomerular and tubular dysfunctions and assessed the accuracy of the most common formula(s) to estimate glomerular filtration rate (GFR) during standard clinical follow-up.

RESULTS

Among the 166 patients who had received aHSCT, 61 underwent kidney functional assessment 1 to 10 years post-transplantation. Twenty-seven patients (44.3%) had a CKD with glomerular impairment, including 20 patients with a GFR < 90 mL/min/1.73 m², and among these, 5 patients < 60 mL/min/1.73 m². Patients with tubular signs had a significantly higher baseline GFR: 112 mL/min/1.73 m² [100; 120] versus 102 [99.0; 112.5] for patients without kidney involvement, and 76 [61; 86] for patients with CKD (p < 0.01). Schwartz, CKiDU25, and EKFC formulas significantly overestimated mGFR, with a P30% ≤ 30%, which could lead to overlooking CKD diagnosis in this population. No patient reached kidney failure.

CONCLUSIONS

In conclusion, our study shows that CKD represents an important long-term sequela for children and adolescents who undergo aHSCT for malignant hemopathies, either with glomerular dysfunction or with the more insidious tubular dysfunction which could potentially impact growth. These patients could benefit from specialized long-term nephrology follow-up. A higher resolution version of the Graphical abstract is available as Supplementary information.

Environmental exposure to lead, mercury, and cadmium is not associated with abnormal kidney function in Korean adolescents

BACKGROUND

We aimed to elucidate the relationship between environmental exposure to lead (Pb), mercury (Hg), and cadmium (Cd) which were measured in blood and the kidney function of adolescents.

METHODS

Cross-sectional study was conducted using data from the Korea National Health and Nutrition Examination Survey from 2010 to 2017. Statistical procedures were performed to analyze the Korean population of adolescents aged 12-17 years. Regression analysis was performed, and covariates included age, sex, body mass index, smoking status, and other heavy metal levels.

RESULTS

The median blood levels of Pb, Hg, and Cd were 1.165 μg/dL, 1.805 μg/L, and 0.304 μg/L, respectively. Adolescents with Pb levels in the highest quartile (> 1.454 μg/dL) had a 3.35 mL/min/1.73 m²-lower estimated glomerular filtration rate using creatinine (eGFR_cr) (95% confidence interval (CI), -6.03 to -0.68 mL/min/1.73 m²) compared to those in the lowest quartile (< 0.856 μg/dL) in the unadjusted model. However, there was no association between the blood Pb level and eGFR_cr in the adjusted model. Levels of Hg and Cd were not associated with eGFR_cr in either model. High blood levels of all three heavy metals were not associated with the risk of hypertension.

CONCLUSIONS

There was no association between increased blood levels of Pb, Hg, and Cd; eGFR_cr; and increased risk of hypertension in Korean adolescents who were exposed to relatively low levels of heavy metals.

Evaluation of novel glomerular filtration rate estimation equations in adolescents and young adults with type 1 diabetes

AIMS

Individuals with type 1 diabetes (T1D) are at an increased risk of chronic kidney disease making estimation of glomerular filtration rate (eGFR) an important component of diabetes care. Which eGFR equation is most appropriate to use in patients with T1D during the transition to adult care is unclear. We, therefore, sought to evaluate the performance of five eGFR equations in adolescents and young adults with T1D.

METHODS

Measured iohexol-based glomerular filtration rate was compared to the Chronic Kidney Disease and Epidemiology Collaboration (CKD-EPI) eGFR, Chronic Kidney Disease in Children (CKiD) eGFR, and three recently developed age-adjusted versions of these in 53 patients with T1D and preserved GFR using bias, precision, and accuracy.

RESULTS

The best performance was found in the sex-dependent CKiD equation (bias: -0.8, accuracy: 11.8 ml/min/1.73 m²). Bias and accuracy (26.4 and 26.8 ml/min/1.73 m²) were worst in the CKD-EPI equation. Age-dependent adjustment improved performance for this equation (bias: 5.3, accuracy: 13.4 ml/min/1.73 m²), but not for the CKiD equation (bias: 15.5, accuracy: 18.8 ml/min/1.73 m²).

CONCLUSION

Age-adjustment improved performance for the CKD-EPI equation, but not for the CKiD equation. The sex-adjusted CKiD equation performed best out of all equations.

Performance of the various serum creatinine-based GFR estimating equations in pediatric kidney transplant recipients, stratified by age and CKD staging

BACKGROUND

Numerous equations are used to estimate glomerular filtration rate (eGFR), based on serum creatinine (SCr), demographic and anthropometric data, none established in pediatric kidney transplant recipients. This study aimed to validate the available SCr-based eGFR equations in comparison with a measured (mGFR), stratified by chronic kidney disease (CKD) stage and age at the time of testing.

METHODS

One hundred twenty-seven pediatric kidney transplant recipients with 411 mGFR values (plasma clearance of iothalamate) were enrolled in this retrospective study. The bias, precision, and accuracy (percentage of estimates within 10% and 30% of mGFR) of five SCr eGFR equations (original Schwartz, CKiDSCr equation, Pottel, Modification of Diet in Renal Disease (MDRD), and Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI)) were assessed.

RESULTS

Height-independent Pottel equation performed well across all the categories of age and CKD staging. CKiDSCr equation performed well in CKD stages II-V. The CKiDSCr equation had a lower bias in children < 15 years of age, while MDRD and CKD-EPI equations had less bias in children > 15 years. Overall, both the Pottel and CKiDSCr equations had high accuracy (80%) and low bias (< 5 ml/min/1.73 m²). In contrast, the original Schwartz, MDRD, and CKD-EPI equations displayed high bias and low precision/accuracy.

CONCLUSIONS

Given their low bias and high accuracy across ages and CKD stages, the Pottel or the CKiDSCr equation is better to assess eGFR in pediatric kidney transplant recipients. The Pottel equation outperformed other eGFR equations in adolescents.

The spectrum of kidney function alterations in adolescents with a solitary functioning kidney

BACKGROUND

A precise assessment of glomerular filtration rate is key to delineate the care of children with a solitary functioning kidney (SFK). Data regarding measured GFR (mGFR) in this population is restricted to a single study of 77 individuals, which suggested that a GFR estimation (eGFR) method based on creatinine and cystatin C (eGFR-CKiD2) performed better than Schwartz's equation (eGFR-Schwartz).

METHODS

We measured GFR in 210 consecutive adolescents (7 to 22 years old) with an SFK referred to our institution between 2014 and 2019 and in 43 young candidates for kidney donation (18 to 25 years old). We compared the distribution of mGFR in both groups and determined the factors associated with reduced mGFR in adolescents with an SFK. We further compared different eGFR formulas with mGFR and assessed the association of mGFR and eGFRs with PTH and FGF23, two early indicators of GFR reduction.

RESULTS

While adolescents with an SFK had a similar median mGFR to healthy controls (103 ± 24ml/min/1.73m² vs. 107 ± 12 ml/min/1.73m²), the fraction of individuals with an mGFR below 90 ml/min/1.73m² was higher in patients with SFK (23% vs. 5% in controls; P = 0.005). Multiple linear regression identified older age, ipsilateral abnormalities of the urinary tract, lack of compensatory hypertrophy, and treated hypertension as independent factors associated with reduced mGFR. A smaller bias using eGFR-Schwartz (95% confidence interval (95%CI): 3 to 7) was revealed when compared to other eGFR. Compared to eGFR-Schwartz, mGFR showed a stronger correlation with PTH (r = 0.04 vs. r = 0.1) and FGF23 (r = 0.03 vs. r = 0.05).

CONCLUSION

SFK is not a benign condition, since 20% of the patients display altered kidney function. Our results raise caution regarding the use of the cystatin-based equation. mGFR shows a better ability than eGFR-Schwartz to differentiate patients showing early homeostatic adaptation to GFR reduction.

Clinical and Histopathological Factors Influencing IgA Nephropathy Outcome

IgA nephropathy (IgAN) is the most frequent primary glomerulonephritis worldwide. Due to its heterogenicity, there is a need to establish robust biomarkers for IgAN, to support treatment decisions and evaluate the risk of progression to end-stage renal disease. Using both clinical and histopathological data, derived from renal biopsies, we aimed to find predictors of renal function deterioration and proteinuria reduction. Clinical and histopathological data of 80 patients with biopsy proven IgAN were analyzed. In a multivariate logarithmic regression model, the presence of endocapillary hypercellularity (E1) predicted a decline in estimated glomerular filtration rate (eGFR)of at least 50% with an odds ratio (OR) of 15.2, whereas serum albumin concentration had a negative influence on eGFR deterioration (OR 0.2). In the second multivariate model, the extent of interstitial fibrosis predicted the worsening of eGFR by 50% (OR 1.1) and serum albumin concentration had a protective impact (OR 0.1). In the univariate logarithmic regression, both the extent of interstitial fibrosis and the presence of endocapillary hypercellularity negatively correlated with the reduction in proteinuria below 1.0 g/24 h with an OR of 0.2 and 0.9, respectively. In our paper, we confirmed the utility of histopathological variables, especially endocapillary hypercellularity and interstitial fibrosis, and clinical parameters, particularly serum albumin concentration, in the prediction of both a decline in eGFR and a reduction in proteinuria in IgA nephropathy.

[Epidemiology of pediatric chronic kidney disease]

Major advances have been made in the management of children with chronic kidney disease over the past 30 years. However, existing epidemiology data are primarily from kidney replacement therapy registries, and information available at earlier stages of chronic kidney disease is limited. The incidence and prevalence of chronic kidney disease stages 2 to 5 remain poorly understood. However, rare population-based studies suggest that the prevalence of all-stage chronic kidney disease may be as high as 1% of the pediatric population. Congenital disorders including congenital abnormalities of the kidney and urinary tract and hereditary nephropathies account for one-half to two-thirds of pediatric chronic kidney disease cases in middle and high-income countries, whereas acquired nephropathies seem to predominate in low-income countries. The progression of chronic kidney disease is slower in children with congenital disorders than in those with acquired nephropathy, particularly glomerular disease, resulting in a lower proportion of congenital abnormalities of the kidney and urinary tract as a cause of end-stage kidney disease compared to less advanced stages of chronic kidney disease. The incidence of kidney replacement therapy in the pediatric population ranged by country from 1 to 14 per million children of the same age in 2018 (approximately 8 per million children in France) in patients younger than 20 years. The prevalence of kidney replacement therapy in children under 20 years of age in 2018 ranged from 15-30 per million children in some Eastern European and Latin American countries to 100 per million children in Finland and the United States (56 per million children in France). Most children with end-stage kidney disease initiate kidney replacement therapy with dialysis (more frequently hemodialysis than peritoneal dialysis). In about 20% of cases, the initial kidney replacement therapy modality is a pre-emptive kidney transplantation. In high-income countries, 60-80% of prevalent children with end-stage kidney disease live with a functioning transplant (75% in France). While the survival of children with chronic kidney disease has continuously improved over time, mortality remains about 30 times higher than in the general pediatric population.

Safe Limits of Contrast Media for Contrast-Induced Nephropathy: A Multicenter Prospective Cohort Study

Background: The safe level of contrast media volume (CV) is an important modifiable risk factor for contrast-induced nephropathy (CIN). The safe limit of CV remains unclear and is limited to single-center studies. Our objective was to determine the association between the ratio of contrast volume-to-glomerular filtration (CV/GFR) and CIN in patients undergoing coronary angiography (CAG) or percutaneous coronary intervention (PCI). Methods: We assessed the association between CV/GFR and the risk of CIN in 4,254 patients undergoing CAG or PCI from the year 2013 to 2016 and enrolled in the REICIN (REduction of rIsk for Contrast-Induced Nephropathy), a prospective, multicenter, observational cohort study. CV/GFR was calculated at the five primary GFR equation. Results: Sixty-nine (1.7%) patients with a median contrast volume-to-chronic kidney disease epidemiology collaboration (CV/CKD-EPI) ratio of 2.16 (1.30-3.93) have suffered from CIN. The CV/CKD-EPI demonstrated the best performance of model fit, discrimination (area under curve = 0.736), calibration, reclassification, and equation conciseness (1 variable). The CV/CKD-EPI ≥1.78 was the statistical significance associated with CIN [adjusted odds ratio, 4.64 (2.84-7.56); p < 0.001]. Furthermore, similar results were found in the subgroup analyses. Conclusions: The CV/CKD-EPI showed the best performance in patients undergoing CAG or PCI. CV/CKD-EPI ≥1.78 could be a more reliable and convenient predictor of CIN. Intraprocedural preventive measures should include a priori calculation of CV/GFR to limit contrast volume.

Chronic kidney disease consecutive to chemotherapy for chondroblastic osteosarcoma: A report on 6 pediatric cases

BACKGROUND

The management of osteosarcoma in children and adolescents is based on poly-chemotherapy including several nephrotoxic drugs (e.g. ifosfamide, methotrexate, and cisplatinum). Chronic renal toxicity is a frequent complication but stage 5 chronic kidney disease requiring dialysis is rare. We report here a series of six pediatric patients with osteosarcoma displaying chronic kidney disease after chemotherapy.

CASE-DIAGNOSIS/TREATMENT

We retrospectively reviewed the medical charts, mainly for clinical history, timing between chemotherapy and development of tubulopathy and CKD, type of therapies and global evolution (chronic dialysis and further renal transplantation, n=2; death, n=1). Notably, all patients suffered from chondroblastic osteosarcoma.

CONCLUSIONS

Advanced chronic kidney disease can be a complication of osteosarcoma management that could more frequently lead to dialysis and further transplantation. It would be interesting to identify specific risk factors of such renal toxicity. The chondroblastic sub-type may be associated with such susceptibility, but this needs to be confirmed.

The Association of Low Vitamin K Status with Mortality in a Cohort of 138 Hospitalized Patients with COVID-19

It has recently been hypothesized that vitamin K could play a role in COVID-19. We aimed to test the hypotheses that low vitamin K status is a common characteristic of patients hospitalized with COVID-19 compared to population controls and that low vitamin K status predicts mortality in COVID-19 patients. In a cohort of 138 COVID-19 patients and 138 population controls, we measured plasma dephosphorylated-uncarboxylated Matrix Gla Protein (dp-ucMGP), which reflects the functional vitamin K status in peripheral tissue. Forty-three patients died within 90 days from admission. In patients, levels of dp-ucMGP differed significantly between survivors (mean 877; 95% CI: 778; 995) and non-survivors (mean 1445; 95% CI: 1148; 1820). Furthermore, levels of dp-ucMGP (pmol/L) were considerably higher in patients (mean 1022; 95% CI: 912; 1151) compared to controls (mean 509; 95% CI: 485; 540). Cox regression survival analysis showed that increasing levels of dp-ucMGP (reflecting low vitamin K status) were associated with higher mortality risk (sex- and age-adjusted hazard ratio per doubling of dp-ucMGP was 1.49, 95% CI: 1.03; 2.24). The association attenuated and became statistically insignificant after adjustment for co-morbidities (sex, age, CVD, diabetes, BMI, and eGFR adjusted hazard ratio per doubling of dp-ucMGP was 1.22, 95% CI: 0.82; 1.80). In conclusion, we found that low vitamin K status was associated with mortality in patients with COVID-19 in sex- and age-adjusted analyses, but not in analyses additionally adjusted for co-morbidities. Randomized clinical trials would be needed to clarify a potential role, if any, of vitamin K in the course of COVID-19.

Development and Validation of a Modified Full Age Spectrum Creatinine-Based Equation to Estimate Glomerular Filtration Rate : A Cross-sectional Analysis of Pooled Data

BACKGROUND

The Chronic Kidney Disease in Children Study (CKiD) equation for children and the Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation for adults are recommended serum creatinine (SCr)-based calculations for estimating glomerular filtration rate (GFR). However, these equations, as well as their combination, have limitations, notably the problem of implausible changes in GFR during the transition from adolescence to adulthood and overestimation of GFR in young adults. The full age spectrum (FAS) equation addresses these issues but overestimates GFR when SCr levels are low.

OBJECTIVE

To develop and validate a modified FAS SCr-based equation combining design features of the FAS and CKD-EPI equations.

DESIGN

Cross-sectional analysis with separate pooled data sets for development and validation.

SETTING

Research and clinical studies (n = 13) with measured GFR available.

PATIENTS

11 251 participants in 7 studies (development and internal validation data sets) and 8378 participants in 6 studies (external validation data set).

MEASUREMENTS

Clearance of an exogenous marker (reference method), SCr level, age, sex, and height were used to develop a new equation to estimate GFR.

RESULTS

The new European Kidney Function Consortium (EKFC) equation is a FAS equation with low bias (-1.2 mL/min/1.73 m² [95% CI, -2.7 to 0.0 mL/min/1.73 m²] in children and -0.9 mL/min/1.73 m² [CI, -1.2 to -0.5 mL/min/1.73 m²] in adults) across the FAS (2 to 90 years) and SCr range (40 to 490 µmol/L [0.45 to 5.54 mg/dL]) and with fewer estimation errors exceeding 30% (6.5% [CI, 3.8% to 9.1%] in children and 3.1% [CI, 2.5% to 3.6%] in adults) compared with the CKiD and CKD-EPI equations.

LIMITATION

No Black patients were included.

CONCLUSION

The new EKFC equation shows improved accuracy and precision compared with commonly used equations for estimating GFR from SCr levels.

PRIMARY FUNDING SOURCE

Swedish Research Council (Vetenskapsrådet).

Creatinine-Based Formulae Poorly Match in the Classification of Hypofiltration or Hyperfiltration in a General Population of Adolescents: A Retrospective Analysis of a Cross-Sectional Study

Pediatric formulae to estimate glomerular filtration rate (eGFR) give a broad range of values. Their consistency in assigning the subjects as hypofiltrating or hyperfiltrating is unknown. In 1993 apparently healthy adolescents (53.4% females) aged 14-17 years, we investigated the concordance of six creatinine-based formulae in the classification of the subjects into ≤ 5th or ≥95th percentile of eGFR, and the between-groups difference in the prevalence of cardiometabolic risk factors. Mean eGFR varied between 77 and 121 mL/min/1.73 m². Arbitrary setting of hypofiltration or hyperfiltration to 5% returned 46 males and 53 females. At least one formula classified 89 males and 99 females as hypofiltrating and 105 males and 114 females as hyperfiltrating. All six formulae concordantly classified 15 males and 17 females as hypofiltrating and 9 and 14, respectively, as hyperfiltrating. Pairwise, formulae consistently classified hypofiltration in 42-87% of subjects with hyperfiltration in 28-94%. According to two out of the six formulae, hyperfiltration was associated with an increased prevalence of obesity and obesity-associated comorbidities. Hypofiltrating subjects did not manifest chronic kidney disease-associated comorbidities. Further studies in different populations of healthy adolescents are needed before it is possible to conclude which creatinine-based formula is appropriate for the classification of hypofiltration and hyperfiltration in nonclinical cohorts.

Characterizing the frequency of modifiable histological changes observed on surveillance biopsies in pediatric kidney allograft recipients

BACKGROUND

Rejection is responsible for just under 50% of graft loss in the pediatric kidney transplant population. Early identification and treatment of allograft injury, specifically modifiable pathologies such as subclinical rejection (SCR), calcineurin inhibitor toxicity, and BK virus nephropathy, may improve allograft survival. Protocol surveillance biopsy (SB) currently offers the earliest opportunity for targeted interventions.

METHODS

This is a single-center retrospective review of 215 kidney SBs obtained from 2008 to 2016 in 97 pediatric kidney transplant recipients. SBs were obtained at 6, 12, and 24 months post-transplantation. Frequency of abnormal histologic findings, estimated glomerular filtration rate at time of SB, and SB-related complications were recorded. Data were analyzed to investigate possible time trends and the presence of demographic or clinical associations with abnormal histologic findings.

RESULTS

Potentially modifiable histologic findings were seen in 38.1% of all SBs. SCR was found with increasing frequency across all time points with an estimated 49% increase in the odds of a SCR finding per additional 6 months post-transplantation (aOR 1.49, 95% CI 1.06-2.09, p = 0.022). Among follow-up biopsies in patients who underwent treatment for SCR, 50% had no SCR and 18.8% showed histologic improvement. The complication rate associated with SB was 1.9% (4/215 SBs) and consisted of only minor complications.

CONCLUSIONS

SBs are safe and offer the opportunity to identify and treat modifiable histologic changes in the pediatric kidney transplant population. The performance of SBs for up to 2 years after transplantation can have meaningful clinical impact.

Optimizing Estimated Glomerular Filtration Rate to Support Adult to Pediatric Pharmacokinetic Bridging Studies in Patients with Cystic Fibrosis

BACKGROUND

The estimated glomerular filtration rate (eGFR) is often used to model drug clearance (CL) and scale doses across age and body size. Over their lifetime, patients with cystic fibrosis (CF) receive repeated courses of tobramycin, an antibiotic with eGFR-dependent CL, for the treatment of pulmonary exacerbations. Tobramycin population pharmacokinetic (PK) modeling can be used to decipher the best approach to define eGFR for pediatric bridging studies.

METHODS

Inpatients with CF who received intravenous tobramycin between 1 January 2006 and 30 May 2018 were eligible for inclusion. Encounters without tobramycin concentration measurement or missing covariate data were excluded. Population PK analysis was performed using NONMEM.Covariate models were built  following identification of the base model, with specific emphasis on the effect of different methods of estimating renal function as a covariate of tobramycin CL.

RESULTS

A total of 296 CF patients contributed 1029 care encounters (420 pediatric, 609 adult) and 4352 tobramycin concentrations to this analysis. The median (minimum, maximum) age at encounter was 19 years (0.2, 60), with serum creatinine of 0.60 mg/dL (0.10, 3.41). A two-compartment model best described the observed data, with height and eGFR as significant covariates of tobramycin CL. eGFR was best modeled using a combination of the modified Schwartz and Chronic Kidney Disease Epidemiology Collaboration (CKDEPI) equations expressed in absolute units.

CONCLUSIONS

The CKDEPI equation bridges PK data generated in adults to adolescents with CF better than the current regulatory standard. The eGFR should be expressed in absolute units (mL/min) for PK analyses.

Prospects for improved glomerular filtration rate estimation based on creatinine-results from a transnational multicentre study

BACKGROUND

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) creatinine equation is routinely used to assess renal function but exhibits varying accuracy depending on patient characteristics and clinical presentation. The overall aim of the present study was to assess if and to what extent glomerular filtration rate (GFR) estimation based on creatinine can be improved.

METHODS

In a cross-sectional analysis covering the years 2003-17, CKD-EPI was validated against measured GFR (mGFR; using various tracer methods) in patients with high likelihood of chronic kidney disease (CKD; five CKD cohorts, n = 8365) and in patients with low likelihood of CKD (six community cohorts, n = 6759). Comparisons were made with the Lund-Malmö revised equation (LMR) and the Full Age Spectrum equation.

RESULTS

7In patients aged 18-39 years old, CKD-EPI overestimated GFR with 5.0-16 mL/min/1.73 m2 in median in both cohort types at mGFR levels <120 mL/min/1.73 m2. LMR had greater accuracy than CKD-EPI in the CKD cohorts (P30, the percentage of estimated GFR within 30% of mGFR, 83.5% versus 76.6%). CKD-EPI was generally the most accurate equation in the community cohorts, but all three equations reached P30 above the Kidney Disease Outcomes Quality Initiative benchmark of 90%.

CONCLUSIONS

None of the evaluated equations made optimal use of available data. Prospects for improved GFR estimation procedures based on creatinine exist, particularly in young adults and in settings where patients with suspected or manifest CKD are investigated.

The correlation analysis between the Oxford classification of Chinese IgA nephropathy children and renal outcome - a retrospective cohort study

BACKGROUND

The 2016 Oxford Classification's MEST-C scoring system predicts outcomes in adults with IgA nephropathy (IgAN), but it lacks tremendous cohort validation in children with IgAN in China. We sought to verify whether the Oxford classification could be used to predict the renal outcome of children with IgAN.

METHODS

In this retrospective cohort study, 1243 Chinese IgAN children who underwent renal biopsy in Jinling Hospital were enregistered from 2000 to 2017. The combined endpoint was defined as either a ≥ 50% reduction in estimated glomerular filtration rate (eGFR) or end-stage renal disease (ESRD). We probed into the relevance betwixt the Oxford classification and renal prognosis.

RESULTS

There were 29% of children with mesangial proliferation(M1), 35% with endocapillary proliferation (E1), 37% with segmental sclerosis/adhesion lesion (S1), 23% with moderate tubular atrophy/interstitial fibrosis (T1 25-50% of cortical area involved), 4.3% with severe tubular atrophy/interstitial fibrosis (T2 > 50% of cortical area involved), 44% with crescent in< 25% of glomeruli(C1), and 4.6% with crescent in> 25% of glomeruli (C2). All children were followed for a medial of 7.2 (4.6-11.7) years, 171 children (14%) arrived at the combined endpoint. The multivariate COX regression model revealed that the presence of lesions S (HR2.7,95%CI 1.8 ~ 4.2, P<0.001) and T (HR6.6,95%CI 3.9 ~ 11.3, P<0.001) may be the reason for poorer prognosis in the whole cohort. In contrast, C lesion showed a significant association with the outcome only in children received no immunosuppressive treatment.

CONCLUSIONS

This study revealed that S and T lesions were useful as the long-term renal prognostic factors among Chinese IgAN children.

Augmentation index, a predictor of cardiovascular events, is increased in children and adolescents with primary nephrotic syndrome

BACKGROUND

Arterial stiffness is associated with an increased risk of cardiovascular diseases. Augmentation index (AIx@75), a measure of arterial stiffness and wave reflection, has not been evaluated in patients with primary nephrotic syndrome (PNS). We investigated whether central and peripheral vascular profiles, hemodynamic parameters, and biochemical tests are associated with AIx@75 in PNS patients.

METHODS

This observational study involved 38 children and adolescents with PNS (12.14 ± 3.65 years) and 37 healthy controls (13.28 ± 2.80 years). Arterial stiffness and vascular and hemodynamic parameters were measured noninvasively using the Mobil-O-Graph® (IEM, Stolberg, Germany). In the PNS group, biochemical tests and corticosteroid dosage/treatment time were analyzed.

RESULTS

Peripheral and central systolic blood pressure (SBPp, SBPc) Z-scores were significantly higher in the PNS patients. AIx@75 was significantly higher in the PNS patients (25.14 ± 9.93%) than in controls (20.84 ± 7.18%). In the control group, AIx@75 negatively correlated with weight (r = - 0.369; p = 0.025), height (r = - 0.370; p = 0.024), and systolic volume/body surface (r = - 0.448; p = 0.006). In the PNS group, a univariate linear correlation showed that AIx@75 negatively correlated with weight (r = - 0.360; p = 0.027), height (r = 0.381; p = 0.18), and systolic volume/body surface (r = - 0.447; p < 0.002) and positively with the Z-score of SBPp (r = 0.407; p = 0.011), peripheral diastolic blood pressure (DBPp, r = 0.452; p = 0.004), SBPc (r = 0.416; p = 0.009), DBPc (r = 0.407; p = 0.011), triglycerides (r = 0.525; p = 0.001), and cholesterol [total (r = 0.539; p < 0.001), LDLc (r = 0.420; p = 0.010), and non-HDLc (r = 0.511; p = 0.001)].

CONCLUSIONS

Early abnormalities of AIx@75 and vascular parameters suggest that patients with PNS, even in stable condition, present subclinical indicators for the development of cardiovascular disease.

Neuropsychological and neuroanatomical phenotype in 17 patients with cystinosis

Background

Cystinosis is a rare autosomal recessive disorder caused by intracellular cystine accumulation. Proximal tubulopathy (Fanconi syndrome) is one of the first signs, leading to end-stage renal disease between the age of 12 and 16. Other symptoms occur later and encompass endocrinopathies, distal myopathy and deterioration of the central nervous system. Treatment with cysteamine if started early can delay the progression of the disease. Little is known about the neurological impairment which occurs later. The goal of the present study was to find a possible neuroanatomical dysmorphic pattern that could help to explain the cognitive profile of cystinosis patients. We also performed a detailed review of the literature on neurocognitive complications associated with cystinosis.

Methods

17 patients (mean age = 17.6 years, [5.4–33.3]) with cystinosis were included in the study. Neuropsychological assessment was performed including intelligence (Intelligence Quotient (IQ) with Wechsler’s scale), memory (Children Memory Scale and Wechsler Memory Scale), visuo-spatial (Rey’s figure test) and visuo-perceptual skills assessments. Structural brain MRI (3 T) was also performed in 16 out of 17 patients, with high resolution 3D T1-weighted, 3D FLAIR and spectroscopy sequences.

Results

Intellectual efficiency was normal in patients with cystinosis (mean Total IQ = 93). However the Perceptual Reasoning Index (mean = 87, [63–109]) was significantly lower than the Verbal Comprehension Index (mean = 100, [59–138], p = 0.003). Memory assessment showed no difference between visual and verbal memory. But the working memory was significantly impaired in comparison with the general memory skills (p = 0.003). Visuospatial skills assessment revealed copy and reproduction scores below the 50th percentile rank in more than 70% of the patients. Brain MRI showed cortical and sub-cortical cerebral atrophy, especially in the parieto-occipital region and FLAIR hypersignals in parietal, occipital and brain stem/cerebellum. Patients with atrophic brain had lower Total IQ scores compared to non-atrophic cystinosis patients.

Conclusions

Patients with cystinosis have a specific neuropsychological and neuroanatomical profile. We suggest performing a systematic neuropsychological assessment in such children aiming at considering adequate management.

Estimated Glomerular Filtration Rates Calculated by New and Old Equations in Children and Adolescents With Type 1 Diabetes-What to Do With the Results?

Background: To apply and evaluate various equations for estimated glomerular filtration rates (eGFR) in a large paediatric type 1 diabetes population and compare the eGFR values with urinary creatinine clearances (UCC) in a subset of patients. Methods: Six eGFR formulae applicable for children and adolescents were used for calculation of eGFR values in 36,782 children/adolescents with type 1 diabetes. Via regression models, factors influencing eGFR values were identified. eGFR values were compared with measured UCC in 549 patients. Spearman correlation coefficients were given to assess the relation of eGFR and UCC values. Bland-Altman-Plots with corresponding linear regression were drawn to evaluate the agreement between eGFR and UCC. Results: eGFR values differed widely depending on the formula used, resulting in a percentage of pathological values <60 mL/min/1.73 m2 up to 8%. Regression models showed age, sex, and duration of diabetes as influencing factors. Microalbuminuria was associated with significantly higher eGFR values for all formulae. In comparison of eGFR with UCC, the highest correlation coefficient was 0.33, the lowest 0.01. Bland-Altman-Plots demonstrated graphically a poor agreement between eGFR and UCC, regardless of the formula used. Conclusions: The broad range of eGFR values indicate that an ideal eGFR formula for children and adolescence with T1D is yet missing. The minimal agreement between measured UCC and eGFR values urges us to be careful in application and interpretation of eGFR values regardless of the formula used.

Human C-terminal CUBN variants associate with chronic proteinuria and normal renal function

BACKGROUNDProteinuria is considered an unfavorable clinical condition that accelerates renal and cardiovascular disease. However, it is not clear whether all forms of proteinuria are damaging. Mutations in CUBN cause Imerslund-Gräsbeck syndrome (IGS), which is characterized by intestinal malabsorption of vitamin B12 and in some cases proteinuria. CUBN encodes for cubilin, an intestinal and proximal tubular uptake receptor containing 27 CUB domains for ligand binding.METHODSWe used next-generation sequencing for renal disease genes to genotype cohorts of patients with suspected hereditary renal disease and chronic proteinuria. CUBN variants were analyzed using bioinformatics, structural modeling, and epidemiological methods.RESULTSWe identified 39 patients, in whom biallelic pathogenic variants in the CUBN gene were associated with chronic isolated proteinuria and early childhood onset. Since the proteinuria in these patients had a high proportion of albuminuria, glomerular diseases such as steroid-resistant nephrotic syndrome or Alport syndrome were often the primary clinical diagnosis, motivating renal biopsies and the use of proteinuria-lowering treatments. However, renal function was normal in all cases. By contrast, we did not found any biallelic CUBN variants in proteinuric patients with reduced renal function or focal segmental glomerulosclerosis. Unlike the more N-terminal IGS mutations, 37 of the 41 proteinuria-associated CUBN variants led to modifications or truncations after the vitamin B12-binding domain. Finally, we show that 4 C-terminal CUBN variants are associated with albuminuria and slightly increased GFR in meta-analyses of large population-based cohorts.CONCLUSIONCollectively, our data suggest an important role for the C-terminal half of cubilin in renal albumin reabsorption. Albuminuria due to reduced cubilin function could be an unexpectedly common benign condition in humans that may not require any proteinuria-lowering treatment or renal biopsy.FUNDINGATIP-Avenir program, Fondation Bettencourt-Schueller (Liliane Bettencourt Chair of Developmental Biology), Agence Nationale de la Recherche (ANR) Investissements d'avenir program (ANR-10-IAHU-01) and NEPHROFLY (ANR-14-ACHN-0013, to MS), Steno Collaborative Grant 2018 (NNF18OC0052457, to TSA and MS), Heisenberg Professorship of the German Research Foundation (KO 3598/5-1, to AK), Deutsche Forschungsgemeinschaft (DFG) Collaborative Research Centre (SFB) KIDGEM 1140 (project 246781735, to CB), and Federal Ministry of Education and Research (BMB) (01GM1515C, to CB).

Human C-terminal CUBN variants associate with chronic proteinuria and normal renal function

BACKGROUNDProteinuria is considered an unfavorable clinical condition that accelerates renal and cardiovascular disease. However, it is not clear whether all forms of proteinuria are damaging. Mutations in CUBN cause Imerslund-Gräsbeck syndrome (IGS), which is characterized by intestinal malabsorption of vitamin B12 and in some cases proteinuria. CUBN encodes for cubilin, an intestinal and proximal tubular uptake receptor containing 27 CUB domains for ligand binding.METHODSWe used next-generation sequencing for renal disease genes to genotype cohorts of patients with suspected hereditary renal disease and chronic proteinuria. CUBN variants were analyzed using bioinformatics, structural modeling, and epidemiological methods.RESULTSWe identified 39 patients, in whom biallelic pathogenic variants in the CUBN gene were associated with chronic isolated proteinuria and early childhood onset. Since the proteinuria in these patients had a high proportion of albuminuria, glomerular diseases such as steroid-resistant nephrotic syndrome or Alport syndrome were often the primary clinical diagnosis, motivating renal biopsies and the use of proteinuria-lowering treatments. However, renal function was normal in all cases. By contrast, we did not found any biallelic CUBN variants in proteinuric patients with reduced renal function or focal segmental glomerulosclerosis. Unlike the more N-terminal IGS mutations, 37 of the 41 proteinuria-associated CUBN variants led to modifications or truncations after the vitamin B12-binding domain. Finally, we show that 4 C-terminal CUBN variants are associated with albuminuria and slightly increased GFR in meta-analyses of large population-based cohorts.CONCLUSIONCollectively, our data suggest an important role for the C-terminal half of cubilin in renal albumin reabsorption. Albuminuria due to reduced cubilin function could be an unexpectedly common benign condition in humans that may not require any proteinuria-lowering treatment or renal biopsy.FUNDINGATIP-Avenir program, Fondation Bettencourt-Schueller (Liliane Bettencourt Chair of Developmental Biology), Agence Nationale de la Recherche (ANR) Investissements d'avenir program (ANR-10-IAHU-01) and NEPHROFLY (ANR-14-ACHN-0013, to MS), Steno Collaborative Grant 2018 (NNF18OC0052457, to TSA and MS), Heisenberg Professorship of the German Research Foundation (KO 3598/5-1, to AK), Deutsche Forschungsgemeinschaft (DFG) Collaborative Research Centre (SFB) KIDGEM 1140 (project 246781735, to CB), and Federal Ministry of Education and Research (BMB) (01GM1515C, to CB).

Estimated GFR: time for a critical appraisal

Since 1957, over 70 equations based on creatinine and/or cystatin C levels have been developed to estimate glomerular filtration rate (GFR). However, whether these equations accurately reflect renal function is debated. In this Perspectives article, we discuss >70 studies that compared estimated GFR (eGFR) with measured GFR (mGFR), involving ~40,000 renal transplant recipients and patients with chronic kidney disease (CKD), type 2 diabetes mellitus or polycystic kidney disease. Their results show that eGFR often differed from mGFR by ±30% or more, that eGFR values incorrectly staged CKD in 30-60% of patients, and that eGFR and mGFR gave different rates of GFR decline. Errors were unpredictable, and comparable for equations based on creatinine and/or cystatin C. We argue, therefore, that the persistence of these errors (despite intensive research) suggests that the problem lies with using creatinine and/or cystatin C as markers of renal function, rather than with the mathematical methods used for GFR estimation.

Retrospective cohort study of individuals born with low birthweight: implications for screening practices

Background

Previous studies have established an association between low birthweight (LBW) and future kidney disease, but few have explored the progression of kidney dysfunction through the pediatric years leading up through adolescence and young adulthood.

Methods

To better understand the temporal effects of birthweight on kidney disease progression, we conducted a retrospective cohort study comparing the glomerular filtration rate (GFR) between LBW (<2500 grams) and normal birthweight (NBW) infants who were admitted to the neonatal intensive care unit (NICU) at our institution from 1992 to 2006.

Results

Age at follow-up ranged 1–26 years old. GFR was found to be significantly lower in participants born with LBW than those born with NBW, with a mean difference of 5.5 mL/min/1.73m² (P < 0.01). These differences were found in the adolescent and young adult age group over 9 years of age, specifically in the extremely low birthweight group (ELBW) whose birthweight was less than 1000 grams.

Conclusions

We recommend screening for CKD in ELBW individuals starting at the age of 9 years old, regardless of their previous medical history.

Fundamental problems with pediatric adaptive dosing of carboplatin using nuclear-medicine-based estimates of renal function

BACKGROUND

Carboplatin is often adaptively dosed based on glomerular filtration rate (GFR), usually estimated by nuclear medicine tests. At least five pediatric adaptive dosing formulas have been developed. In an effort to standardize dosing in Children's Oncology Group protocols, we explored methodologic variation in GFR estimation and adaptive-dosing formula performance.

PROCEDURE

Nuclear medicine GFR data from published series of ≥100 children with cancer were compared. Data from patients for whom body surface area, weight, GFR, and tracer half-life were available were used to compare formulas.

RESULTS

Differences in methods used to estimate GFR in children with cancer resulted in highly variable population results, with median GFRs ranging from 96 to 150 mL/min/1.73m² . The choice of adaptive formula had a major impact on calculated dose. When targeting an area under the curve of 7.9 mg/mL • min, the median difference between the formula yielding the lowest and highest carboplatin dose for individual subjects was 289 (range 96-1 737) mg/m² .

CONCLUSIONS

Wide variation in GFR obtained with nuclear-medicine-based tests in children with cancer primarily results from systematic methodologic errors. Formulas for calculating carboplatin dose produce additional and substantial variation that may place children with cancer at unnecessary risk for excessive toxicity or underdosing. These findings indicate a need for the development of a uniform, validated method for GFR determination in children that should be utilized in all centers. Currently, adaptive dosing of carboplatin based on GFR has serious limitations and in most clinical settings should arguably not be used in place of body-surface-area-based dosing.

Impact of errors of creatinine and cystatin C equations in the selection of living kidney donors

Background

Reliable determination of glomerular filtration rate (GFR) is crucial in the evaluation of living kidney donors. Although some guidelines recommend the use of measured GFR (mGFR), many centres still rely on estimated GFR (eGFR) obtained through equations or 24-h creatinine clearance. However, eGFR is neither accurate nor precise in reflecting real renal function. We analysed the impact of eGFR errors on evaluation and decision making regarding potential donors.

Methods

We evaluated 103 consecutive living donors who underwent mGFR via iohexol plasma clearance and eGFR by 51 creatinine- and/or cystatin C-based equations. The cut-off for living donation in our centre is GFR > 80 mL/min for donors >35 years of age or 90 mL/min for those <35 years of age. We analysed the misclassification of donors based on the cut-off for donation-based eGFR.

Results

Ninety-three subjects (90.3%) had mGFR values above (donors) and 10 [9.7% (95% confidence interval 5.4-17)] below (non-donors) the cut-off. In non-donors, most of the equations gave eGFR values above the cut-off, so donation would have been allowed based on eGFR. All non-donors were female with reduced weight, height and body surface. In donors, up to 32 cases showed eGFR below the cut-off, while mGFR was actually higher. Therefore an important number of donors would not have donated based on eGFR alone.

Conclusion

The misclassification of donors around the cut-off for donation is very common with eGFR, making eGFR unreliable for the evaluation of living kidney donors. Whenever possible, mGFR should be implemented in this setting.

Estimating glomerular filtration rate at the transition from pediatric to adult care

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/1.73m²) 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/1.73m²), resulting in a mean change of 23 mL/min/1.73m² 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/1.73m², 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 m²/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.