Validation of child serum creatinine-based prediction equations for glomerular filtration rate

Discrepancies among equations to estimate the glomerular filtration rate for drug dosing decision making in aged patients: a cross sectional study

BACKGROUND

Patients often require adjustments to drug doses due to impaired renal function. Glomerular filtration rate (GFR) estimation using various equations can result in discrepancies, potentially leading to different dose adjustment recommendations.

AIM

To determine the clinical significance of discrepancies observed between different equations used to estimate GFR for drug dose adjustments in a real-world group of patients over 65 years in primary care.

METHOD

The Cockcroft-Gault (CG), Modification of Diet in Renal Disease (MDRD), Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI), and Berlin Initiative Study 1 equations were applied to estimate GFR in a group of patients over 65 years old attending a primary care center. Results were compared using Bland-Altman plots, and limits of agreement (LoA) and overall bias were calculated. Regression analyses were conducted to identify the null difference GFR and the slope of differences for each pairwise comparison.

RESULTS

A total of 1886 patients were analyzed. Differences between patient-adjusted and body surface area (BSA)-normalized versions of the equations were not clinically relevant for dose adjustments, with LoAs below 20 mL/min. However, discrepancies among the original versions of several equations presented LoAs over 30 mL/min. Greater differences were found between CG and MDRD or CKD-EPI equations.

CONCLUSION

Clinically relevant differences in GFR estimation were observed among different equations, potentially impacting drug dose adjustments. However, discrepancies were not considered significant when comparing patient-adjusted and BSA-normalized versions of the equations, particularly for patients with BSA close to the average.

Analysis of long-term renal function in patients with malignant solid tumors: Retrospective analysis using the estimated glomerular filtration rate

BACKGROUND

Childhood cancer survivors are at an increased risk of impaired renal function. The aim of the present study was to assess the frequency of and risk factors for long-term renal dysfunction in patients with solid tumors using the estimated glomerular filtration rate (eGFR).

METHODS

We retrospectively evaluated eGFR in 52 patients with solid tumors (25 females, 27 males) who received chemotherapy and were regularly followed up in our institute. Decreased eGFR was defined as <90 ml/min/1.73 m² . Cases under treatment and of death were excluded.

RESULTS

Median age at the diagnosis of the primary disease was 2.4 years (range, 0.0-23.9 years) and the median follow-up period was 98.4 months (range, 14.4-231.6 months). The mean cumulative incidence of decreased eGFR was 24.7 ± 2.2%. Multivariate analysis showed that decreased eGFR correlated with an older age at diagnosis (≥2.3 years) (hazard ratio 7.330, p = 0.018).

CONCLUSION

Although previous studies have indicated that the risk of long-term nephrotoxicity is higher in patients treated at a younger age, the present study showed that patients treated at an older age were at an increased risk of decreased eGFR.

The salutary effect of peritoneal dialysis catheters on enhanced recovery among high-risk pediatric patients undergoing the left coronary transfer procedure: a cohort study

BACKGROUND

Evidence for peritoneal dialysis catheter (PDC) usage in pediatric patients undergoing surgery for deteriorating cardiac dysfunction is lacking. This investigation explored factors associated with PDC usage and its effectiveness in children with anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA).

METHODS

Eighty-four children undergoing left coronary artery transfer were retrospectively recruited. The primary endpoint was the postoperative ratio of the general ward/[intensive care unit (ICU)] length of stay. Univariable and multivariable analyses were fitted to assess factors related most strongly to PDC and the ratio of general ward/ICU length of stay.

RESULTS

Of the 84 patients, 17 (20.2%) underwent postoperative PDC placement. Patients with extreme cardiac dysfunction [left ventricular ejection fraction (LVEF) ≤25%] were much more likely to require a PDC (OR, 9.88; 95% CI, 2.13-45.76; P = 0.003). Moreover, univariate analysis indicated that concomitant mitral repair significantly decreased the likelihood of PDC placement (OR, 0.25; 95% CI, 0.07-0.85; P = 0.026). In those with cardiac dysfunction (LVEF ≤50%), PDC use was associated with a reduced ratio of ward/ICU length of stay (B, - 1.62; 95% CI, - 2.77- -0.46; P = 0.008), as was age ≤ 12 months (B, - 1.57; 95% CI, - 2.88- -0.26; P = 0.02). At the 1-year follow-up, cardiac improvement was significantly greater in patients with PDC usage than in those without it (P <  0.001), and the number of mitral recoveries was comparable between the groups (64.2% vs. 53.3%, P = 0.434).

CONCLUSION

In cohorts with ALCAPA, PDC placement following surgery may be necessary for patients with extreme cardiac compromise, while concomitant mitral repair can probably reduce their usage rate. PDC is beneficial in conferring an improvement in cardiac and mitral performance. Importantly, after patients are transferred from the ICU, recovery efficiency in the general ward can be enhanced by PDC placement, and hospital discharge can therefore be achieved early, especially for patients younger than 12 months or with LVEF ≤50%.

The Incidence and Risk Factors for Persistent Acute Kidney Injury Following Total Cavopulmonary Connection Surgery: A Single-Center Retrospective Analysis of 465 Children

Background: Acute kidney injury (AKI) after cardiac surgery contributes to adverse outcomes. We aimed to assess the incidence and identify the predictors for persistent AKI after total cavopulmonary connection (TCPC) surgery. Methods: A retrospective study, including 465 children undergoing TCPC surgery from 2010 to 2019, was conducted. We used pRIFLE criteria to define AKI and defined persistent AKI as AKIs occurring between post-operative day1 (POD1) and POD3 and sustaining at least on POD7. Univariate and multivariate logistic regressions were applied to analyze the predictors for persistent AKI. Results: A total of 35.3% patients developed AKI between POD1 to POD3 and 15.5% patents had persistent AKI after TCPC. Patients with persistent AKI had prolonged mechanical ventilation and ICU stay, and had higher rates of renal replacement treatment and reintubation, which was associated with higher hospitalization costs and in-hospital mortality. The independent predictors for persistent AKI were peripheral oxygen saturation (SpO2) upon admission, intraoperative fluid balance, POD0 maximal lactic acid, renal perfusion pressure (RPP), POD0 estimated glomerular filtration rate and POD0 total bilirubin. The areas under receiver operating characteristic curve (AUC) in the total cohort and the subgroup undergoing TCPC surgery after 2017 were 0.75 (95% CI, 0.66-0.82) and 0.87 (95% CI, 0.77-0.97), respectively. The acceptable AUCs (nearly 0.7) were achieved in other 5 subgroups and good calibration ability (p ≥ 0.05) were achieved in the total cohort and all six subgroups. Conclusions: Persistent AKI after TCPC was common and strongly associated with poorer in-hospital outcomes in Chinese pediatric patients. Six perioperative variables, including SpO2, intraoperative fluid balance, POD0 maximal lactic acid, RPP, POD0 moderate-to-severe kidney injury and POD0 total bilirubin, were identified as independent predictors for persistent AKI. Our findings may help to perform an early risk stratification for these vulnerable patients and improve their outcomes.

Population Pharmacokinetics of Milrinone in Infants, Children, and Adolescents

Milrinone is a type 3 phosphodiesterase inhibitor used to improve cardiac output in critically ill infants and children. Milrinone is primarily excreted unchanged in the urine, raising concerns for toxic accumulation in the setting of renal dysfunction of critical illness. We developed a population pharmacokinetic model of milrinone using nonlinear mixed-effects modeling in NONMEM to perform dose-exposure simulations in children with variable renal function. We included children aged <21 years who received intravenous milrinone per clinical care. Plasma milrinone concentrations were measured using a validated liquid chromatography-tandem mass spectrometry assay (range 1-5000 ng/mL). We performed dose-exposure simulations targeting steady-state therapeutic concentrations of 100-300 ng/mL previously established in adults and children with cardiac dysfunction. We simulated concentrations over 48 hours in typical subjects with decreasing creatinine clearance (CrCl), estimated using the updated bedside Schwartz equation. Seventy-four patients contributed 111 plasma samples (concentration range, 4-634 ng/mL). The median (range) postmenstrual age (PMA) was 3.7 years (0-18), and median weight (WT) was 13.1 kg (2.6-157.7). The median serum creatinine and CrCl were 0.5 mg/dL (0.1-3.1) and 117.2 mL/min/1.73 m2 (13.1-261.3), respectively. A 1-compartment model characterized the pharmacokinetic data well. The final model parameterization was: Clearance (L/h) = 15.9*(WT [kg] / 70)0.75 * (PMA1.12 / (67.71.12 +PMA1.12 )*(CrCl / 117)0.522 ; and Volume of Distribution (L) = 32.2*(WT [kg] / 70). A loading dose of 50 µg/kg followed by a continuous infusion of 0.5 µg/kg/min resulted in therapeutic concentrations, except when CrCl was severely impaired at ≤30 mL/min/1.73 m2 . In this setting, a 25 µg/kg loading dose and 0.25 µg/kg/min continuous infusion resulted in therapeutic exposures.

Fluid Overload in Special Pediatric Cohorts With Anomalous Origin of the Left Coronary Artery From the Pulmonary Artery Following Surgical Repair

OBJECTIVE

To investigate the prevalence, risk factors, and clinical outcomes associated with early fluid overload (FO) in a special group of pediatric patients undergoing repair of anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA).

DESIGN

It was a retrospective study performed with multiple variable regression analysis.

SETTING

A single cardiac surgical institution.

PARTICIPANTS

Eighty-eight patients younger than 18 years of age undergoing ALCAPA surgical repair with cardiopulmonary bypass were recruited at the authors' institution from June 2010 to September 2017.

INTERVENTION

None.

MEASUREMENTS AND MAIN RESULTS

Of 88 pediatric patients with ALCAPA after surgical repair, 37.5% developed early FO, defined as fluid accumulation ≥5% within the period from surgery until midnight of postoperative day 1. Patients with early FO were younger, weighed less, and had worse preoperative cardiac dysfunction. With logistic regression analysis, being underweight was confirmed to be a risk factor for FO development (odds ratio, 8.66; 95% confidence interval, 2.83-26.52; p < 0.001). Early FO also predicted severe acute kidney injury, respiratory morbidity, and low cardiac output syndrome after reimplantation procedure. Patients with early FO also had significantly longer mechanical ventilation hours (p  <  0.001), intensive care unit length of stay (p = 0.003), and hospital length of stay (p = 0.009).

CONCLUSION

Early FO ≥5% has been linked to adverse postoperative outcomes in pediatric patients undergoing repair for ALCAPA. The use of restrictive fluid management is crucial for patients who have lower weight and poor myocardial function before and after complex surgical procedures such as in ALCAPA settings.

Long-term renal follow-up of children treated with cisplatin, carboplatin, or ifosfamide: a pilot study

BACKGROUND

Childhood cancer survivors treated with cisplatin, ifosfamide, or carboplatin are at risk for late kidney and blood pressure (BP) abnormalities. Few studies have comprehensively evaluated kidney outcomes and 24-h ambulatory BP monitoring (ABPM) in this population. We aimed to describe chemotherapy-associated acute kidney injury (AKI) and late kidney outcomes using standardized definitions.

METHODS

This was a single-center longitudinal pilot study of 23 children who participated in a previous study during cisplatin, carboplatin, or ifosfamide treatment. Medical charts were reviewed retrospectively. Available patients were approached for a study visit for blood and urine collection, BP measurement, and ABPM. AKI is defined by serum creatinine (SCr) rise (Kidney Disease: Improving Global Outcomes definition [SCr-AKI]). Electrolyte-AKI is defined by hypokalemia, hypophosphatemia, or hypomagnesemia. Chronic kidney disease (CKD) is defined by estimated glomerular filtration rate < 90 mL/min/1.73 m², albuminuria, or proteinuria. Electrolyte-CKD is defined by low serum electrolyte concentration or electrolyte supplementation.

RESULTS

Median age at chemotherapy start was 8.3 years; 9/23 (39%) were boys. Fourteen out of 23 (61%) patients had SCr-AKI during therapy; all developed electrolyte-AKI. Median 5.7 years post-chemotherapy, 7/22 (32%) had CKD, 11/23 (48%) had electrolyte-CKD, and 2/20 (10%) had hypertension. Fifteen out of 23 patients (65%) had either CKD, electrolyte-CKD, or hypertension. In ten patients available for a study visit (median 4.9 years post-chemotherapy), 1/10 (10%) had hypertension by ABPM; none had masked or white coat hypertension. All ten had at least one kidney abnormality (CKD, electrolyte-CKD, office pre-hypertension, or abnormal ABPM).

CONCLUSIONS

Using standardized outcome definitions, children treated with cisplatin, carboplatin, or ifosfamide have a high prevalence of late kidney abnormalities. Research must elucidate best practice for post-cancer treatment follow-up and kidney complication treatment.

M, Mehta L. R. Recognition and management of acute kidney injury in children: The ISN 0by25 Global Snapshot study

BACKGROUND

In low and middle-income countries, reliable data on the epidemiology of childhood acute kidney injury (AKI) is lacking. The Global Snapshot, conducted by the ISN "0by25" AKI initiative, was a world-wide cross-sectional, observational study to evaluate AKI in hospitalized patients. Here we report the pediatric results of this study.

PATIENTS AND METHODS

We prospectively collected data on children who met the Kidney Disease Improving Global Outcomes AKI criteria during a 10-week window in late 2014. AKI risk factors, etiological factors, management and outcomes were recorded using standardized forms and protocols. Countries were classified according to their 2014 gross national income (GNI) per person into high-income countries (HIC), upper-middle income countries (UMIC) and low and low-middle income countries (LLMIC). Need for renal replacement therapy, mortality, and renal recovery were assessed 7 days after AKI diagnosis or at hospital discharge, whichever came first.

RESULTS

92 centers from 41 countries collected data on 354 pediatric AKI patients; 53% of the children developed AKI while hospitalized and 47% in the community. The most common etiological factors for AKI differed across GNI categories as well as between patients with community-acquired vs. hospital-acquired AKI. Children from HIC were younger, and larger proportion of AKI in this group were due to post-surgical complications vs. other etiologies when compared to other income categories. In patients with hypotension as the cause of AKI, the adjusted risk of death was almost 10-fold higher compared to patients without hypotension as an etiological factor for AKI development. Mortality was similar within AKI stages in HIC and UMIC. In LLMIC, patients with the highest AKI level of severity had higher mortality than patients in higher income categories. Patients from LLMIC and UMIC had a 57-fold and 11 fold higher adjusted risk of death, respectively, compared to patients from HIC.

CONCLUSION

In resource-limited countries, pediatric AKI-associated mortality is disproportionately higher when compared to high-resource areas, especially among patients with more severe AKI.

Comparison of methods to estimate glomerular filtration rate in paediatric oncology patients

AIMS

Glomerular filtration rate (GFR) is estimated daily in paediatric oncology patients; however, few equations, particularly ones that do not include serum creatinine, have been evaluated in this population. We aimed to compare the predictive performance of different equations available to estimate GFR in paediatric oncology patients.

METHODS

GFR was measured (mGFR) in paediatric oncology patients based on a chromium 51-labeled ethylene diamine tetraacetic acid excretion test. GFR was estimated (eGFR) in these same patients using equations identified from the literature. mGFR and eGFR values were compared, and the predictive performance of various eGFR equations was assessed in terms of their bias, precision and accuracy.

RESULTS

In total, 124 mGFR values ranging from 7 to 146 mL/min were available for analysis from 73 children. Twenty-two equations were identified from the literature. The Flanders metadata equation displayed the lowest absolute bias (mean error of 0.9 mL/min) and the greatest precision (root mean square error of 13.1 mL/min). The univariate Schwartz equation predicted the highest percentage (81.5%) of eGFR values within 30% of mGFR values, and the Rhodin fat-free mass equation predicted the highest percentage (37.1%) of eGFR values within 10% of mGFR values.

CONCLUSIONS

A number of equations were identified that could be used to estimate renal function in paediatric oncology patients; however, none was found to be highly accurate. The Flanders metadata equation and univariate Schwartz performed the best in this study, and we would suggest that these two equations may be used cautiously in paediatric oncology patients for clinical decision making, understanding their limitations.

Levosimendan for Pediatric Anomalous Left Coronary Artery From the Pulmonary Artery Undergoing Repair: A Single-Center Experience

Objectives: Our aim was to retrospectively evaluate the benefit of levosimendan in certain complicated congenital heart procedures such as the pediatric anomalous origin of the left coronary artery from the pulmonary artery (ALCAPA) with moderate or severe cardiac dysfunction and its repair. Study Design: We enrolled 40 pediatric patients with ALCAPA and moderate or severe left ventricular dysfunction. Patients who had a preoperative left ventricular ejection fraction (LVEF) of 50% or less and had undergone the surgical correction of their coronary artery through cardiopulmonary bypass met the criteria of our study. Twenty patients were given 0.1-0.2 μg/kg/min levosimendan at the induction of anesthesia, which lasted for 24 h. The remaining 20 patients were not given levosimendan. Results: The mean preoperative LVEF in the levosimendan group was significantly lower than that in the non-levosimendan group (22.5 ± 10.7% vs. 31.8 ± 8.1%, p = 0.004). On postoperative day 7, the LVEF in the levosimendan group was still significantly lower (27.1 ± 8.9% vs. 37.5 ± 11.0%, p = 0.002). There was no significant difference in ΔLVEF detected on day 7 [median 30.8%, interquartile range (IQR) -4.4 to 63.5% vs. median 15.1%, IQR -3.5 to 40.0%, p = 0.560] or at follow-up of about 180 days (median 123.5%, IQR 56.1-222.6% vs. median 80.0%, IQR 36.4-131.3%, p = 0.064). There was no significant difference between the two groups in postoperative vasoactive-inotropic score (VIS) at any of the time points of 1, 6, 12, 24, and 48 h (p = 0.093). Three patients had to be supported by extracorporeal membrane oxygenation when difficulty appeared in weaning off cardiopulmonary bypass because of low cardiac output in the non-levosimendan group, but no patient needed extracorporeal membrane oxygenation after levosimendan infusion (p = 0.231). The length of intensive care unit stay (median 10.5 days, IQR 7.3-39.3 days vs. median 4.0 days, IQR 2.0-10.0 days, p = 0.002) and duration of mechanical ventilation (median 146.0 h, IQR 76.5-888.0 h vs. median 27.0 h, IQR 11.0-75.0 h, p = 0.002) were revealed to be longer in the levosimendan group. Peritoneal dialysis occurred in eight patients (40%) in the levosimendan group and two patients (10%) in the non-levosimendan group (p = 0.028). No significant difference was revealed in all-cause mortality within 180 days, which occurred in two patients (10%) in the levosimendan group and one (5%) in the non-levosimendan group (p = 1.00). Conclusion: Levosimendan's unique pharmacological properties have strong potential for cardiac function recovery among pediatric patients with ALCAPA with impaired left ventricular function who have undergone surgical repair.However, any improvement from levosimendan on postoperative outcomes or mortality was not substantiated by this study and must be investigated further.

Validation of serum creatinine-based formulae in pediatric renal transplant recipients

BackgroundAccurate monitoring of kidney function is important post-renal transplant; however, the routine use of measured glomerular filtration rate (GFR) or addition of newer serum markers is prohibitively expensive for routine clinical use, especially in children. We validated the modified Schwartz formula in pediatric renal transplant recipients across a range of demographic and clinical characteristics.MethodsIn a retrospective cohort study with nested cross-sectional analysis, we compared 505 measurements of estimated GFR using serum creatinine to simultaneous diethylenetriaminepentaacetic acid (DTPA) nuclear GFR (nGFR) measurements from 173 pediatric kidney transplant recipients who were < 18 years of age from 1 January 2001 to 31 December 2012 accounting for repeated measures.ResultsAmong 173 children, 62% were males, 85% with nGFR of ≥60 ml/min/1.73 m², and the median age at transplant was 13.6 years (interquartile range 8.3-16 years). Overall, the modified Schwartz and Pottel formulae had better bias (0.07 and -0.03 ml/min/1.73 m², respectively) and accuracy within 30% (both 84.4%) in comparison to Lyon and Zappitelli formulae. The 30% accuracy varied for girls and children <5 and >15 years.ConclusionModified Schwartz is a practical, non-invasive, and a valid bedside tool that provides a valid measurement of GFR in pediatric kidney transplant recipients.

The incidence of pediatric acute kidney injury is increased when identified by a change in a creatinine-based electronic alert

A prospective national cohort study was undertaken to collect data on all cases of pediatric (under 18 yrs of age) acute kidney injury (AKI) identified by a biochemistry-based electronic alert using the Welsh National electronic AKI reporting system. Herein we describe the utility and limitation of using this modification of the KDIGO creatinine-based system data set to characterize pediatric AKI. Of 1,343 incident episodes over a 30-month period, 34.5% occurred in neonates of which 83.8% were AKI stage 1. Neonatal 30-day mortality was 4.1%, with 73.3% of this being accounted for by patients treated in an Intensive Care Unit. In the non-neonatal group, 76.1% were AKI stage 1. Hospital-acquired AKI accounted for 40.1% of episodes while community-acquired AKI represented 29.4% of cases within which 33.9% were admitted to hospital and 30.5% of cases were unclassified. Non-neonatal 30-day mortality was 1.2%, with half of this accounted for by patients treated in the Intensive Care Unit. Nonrecovery of renal function at 30 days occurred in 28% and was significantly higher in patients not admitted to hospital (45% vs. 20%). The reported incidence of AKI in children was far greater than previously reported in studies reliant on clinical identification of adult AKI or hospital coding data. Mortality was highest in neonates and driven by those in the Intensive Care Unit. Nonrecovery of renal function and persistent renal impairment was more common in non-neonates and was especially high in patients with community-acquired AKI who were not hospitalized.

Applicability of various estimation formulas to assess renal function in Chinese children

BACKGROUND

This study was to evaluate the relative applicability of the most commonly used estimation formulas for renal glomerular filtration rate (GFR) of Chinese children with chronic kidney disease (CKD).

METHODS

One hundred CKD patients of less than 17 years old were divided into two groups by sex which was further categorized into five subgroups based on CKD staging according to the "reference" GFR (rGFR) determined by Tc-99m-DTPA renal dynamic imaging. Four GFR markers including serum cystatin C (CysC), β2-microglobulin, creatinine, and blood urea nitrogen were measured.

RESULTS

Among all four markers, CysC best reflected the extent of glomerular damages for CKD stage 1. The value for estimation of GFR (eGFR) was derived from five different formulas either over-estimated or underestimated GFR as referenced to rGFR, and the extent of deviations was dependent on gender, age and CKD stage. The Counahan-Barratt formula and the Schwartz formula gave the most accurate estimations of GFR for CKD stages 1 and 2-3, respectively regardless of gender and age differences. Receiver operating characteristic analyses indicated that the Counahan-Barratt formula has the highest diagnostic accuracy.

CONCLUSION

The Counahan-Barratt formula provides the best approximation to rGFR, thereby the highest applicability to Chinese children with CKD of different genders, ages and CKD stages.

Estimation of glomerular filtration rate with and without height: effect of age and renal function level

BACKGROUND

The current glomerular filtration rate (GFR) equation (CKiD) may be less accurate in adolescents and children with higher GFR.

METHODS

This was a retrospective study (n = 161, 247 (99)mTc DTPA-GFRs). Six equations were evaluated for bias, accuracy, and low GFR diagnosis: (1) CKiD; (2) historic center; (3) Hoste(age); (4) Hoste(height); (5) modified Pottel; (6) Gao. Children with ≥ vs. <90 ml/min/1.73 m(2)) and < vs. ≥16 years were compared. Two adult equations were evaluated in children ≥16 years.

RESULTS

Most equations underestimated GFR by 1-14 % in the higher GFR group, least so for Hoste(age). In the low GFR group, Hoste(age) and historic center overestimated GFR significantly more than CKiD (p < 0.05). Accuracy (within 30 % GFR) was similar across equations and GFR subgroups (66-86 %). In the ≥16 years group, CKiD underestimated GFR by ∼10 %, vs. ∼3 % for Hoste(height). Accuracy was 5-10 % lower in the older group and most equations were more sensitive than specific for detecting low GFR; this discrepancy was less for the Hoste equations. Adult equations were highly inaccurate.

CONCLUSIONS

GFR estimation in older children and with higher GFR is suboptimal. The Hoste(height) may be an alternative GFR estimation method; Hoste(age) may allow for height-independent GFR estimation in patients with normal GFR.

Association of definition of acute kidney injury by cystatin C rise with biomarkers and clinical outcomes in children undergoing cardiac surgery

IMPORTANCE

Research has identified improved biomarkers of acute kidney injury (AKI). Cystatin C (CysC) is a better glomerular filtration rate marker than serum creatinine (SCr) and may improve AKI definition.

OBJECTIVE

To determine if defining clinical AKI by increases in CysC vs SCr alters associations with biomarkers and clinical outcomes.

DESIGN, SETTING, AND PARTICIPANTS

Three-center prospective cohort study of intensive care units in New Haven, Connecticut, Cincinnati, Ohio, and Montreal, Quebec, Canada. Participants were 287 patients 18 years or younger without preoperative AKI or end-stage renal disease who were undergoing cardiac surgery. The study dates were July 1, 2007, through December 31, 2009.

EXPOSURES

For biomarker vs clinical AKI associations, the exposures were first postoperative (0-6 hours after surgery) urine interleukin 18, neutrophil gelatinase-associated lipocalin, kidney injury molecule 1, and liver fatty acid-binding protein. For clinical AKI outcome associations, the exposure was Kidney Disease: Improving Global Outcomes AKI definition (based on SCr or CysC).

MAIN OUTCOMES AND MEASURES

Clinical AKI, length of stay, and length of mechanical ventilation. We determined areas under the receiver operating characteristic curve and odds ratios for first postoperative biomarkers to predict AKI.

RESULTS

The SCr-defined vs CysC-defined AKI incidence differed substantially (43.6% vs 20.6%). Percentage agreement was 71% (κ = 0.38); stage 2 or worse AKI percentage agreement was 95%. Interleukin 18 and kidney injury molecule 1 discriminated for CysC-defined AKI better than for SCr-defined AKI. For interleukin 18 and kidney injury molecule 1, the areas under the receiver operating characteristic curve were 0.74 and 0.65, respectively, for CysC-defined AKI, and 0.66 and 0.58, respectively, for SCr-defined AKI. Fifth (vs first) quintile concentrations of both biomarkers were more strongly associated with CysC-defined AKI. For interleukin 18 and kidney injury molecule 1, the odds ratios were 16.19 (95% CI, 3.55-73.93) and 6.93 (95% CI, 1.88-25.59), respectively, for CysC-defined AKI vs 6.60 (95% CI, 2.76-15.76) and 2.04 (95% CI, 0.94-4.38), respectively, for SCr-defined AKI. Neutrophil gelatinase-associated lipocalin and liver fatty acid-binding protein associations with both definitions were similar. The CysC definitions and SCr definitions were similarly associated with clinical outcomes of resource use.

CONCLUSIONS AND RELEVANCE

Compared with the SCr-based definition, the CysC-based definition is more strongly associated with urine interleukin 18 and kidney injury molecule 1 in children undergoing cardiac surgery. Consideration should be made for defining AKI based on CysC in clinical care and future studies.

Long-term mortality associated with acute kidney injury in children following congenital cardiac surgery

OBJECTIVE

Children undergoing congenital cardiac surgery (CCS) are at increased risk for acute kidney injury (AKI) due to a number of factors. Recent evidence suggests AKI may influence mortality beyond the immediate postoperative period and hospitalization. We sought to determine the association between renal failure and longer-term mortality in children following CCS.

METHODS

Our Study population included all patients that underwent cardiac surgery at our institution during a period of 3 years from 2004 through 2006. The primary definition of acute renal injury was based on pRIFLE using estimated creatinine clearance (pRIFLE eCCL).

RESULTS

Predictors of mortality. Age, single ventricle status, and renal failure as defined by pRIFLE stage F were associated with mortality. The hazard ratio for a patient with renal failure as defined by pRIFLE stage F was 3.82 (CI 1.89-7.75). Predictors of AKI as defined by pRIFLE. Duration of cardiopulmonary bypass (CPB) and age were the only variables associated with pRIFLE by univariate analysis. However, in the ordinal or survival model, age was the only variable associated with renal failure as defined by pRIFLE. As patient age increases from 0.30 to 3.5 years, the risks of having renal injury (pRIFLE stage I) or failure (pRIFLE stage F) decreases (OR 0.44, CI 0.21-0.94).

CONCLUSION

Mortality risk following CCS is increased in younger patients and those experiencing postoperative renal failure as defined by pRIFLE for a period of time that extends well beyond the immediate postoperative period and the time of hospitalization.

Evaluation of renal function after successful treatment for unilateral, non-syndromic Wilms tumor

Impaired renal function may occur in experimental animals following surgical removal of most functioning renal tissue ("hyperfiltration injury"). Although end-stage renal disease is uncommon among long-term survivors of unilateral, non-syndromic Wilms tumor, concern has been expressed that there may be an increased risk of less serious, but progressive, renal function impairment among these individuals. The recent development of equations for estimating glomerular filtration rate (eGFR) has facilitated the study of renal function in Wilms tumor survivors. However, the estimating equations were developed to categorize individuals with chronic kidney disease and have significant limitations with regard to the accuracy of individual GFR estimates. These limitations must be considered when utilizing the estimating equations in cross-sectional or longitudinal evaluations of renal function in cohorts of patients who have been treated successfully for Wilms tumor or other childhood cancers.

A new equation to estimate the glomerular filtration rate in children, adolescents and young adults

BACKGROUND

A new estimated glomerular filtration rate (eGFR) equation, designed for isotope dilution mass spectrometry-standardized serum creatinine (Scr), is presented for use in children, adolescent boys and girls and young adults.

METHODS

The new equation, eGFR = 107.3/(Scr/Q), is based on the concept of normalized Scr: Q is the normalization value and is considered as the Scr concentration for the average healthy child, adolescent or young adult of a specific height (L) and is modeled as a height-dependent polynomial of the fourth degree.

RESULTS

The well-known Schwartz equation [eGFR = kL/Scr, k = 0.413 (Schwartz) or k = 0.373 (Schwartz-Lyon)] for children between 1 and 14 years can be seen as a special case of the new equation for which the Q-polynomial is simplified to a linear equation: Q = 0.0035 × L (cm). The new eGFR equation has been validated in a data set of n = 750 children, adolescents and young adults aged 10-25, against the true GFR (inulin method), and outperforms the selected (but most used) creatinine-based eGFR equations for children, mainly in the healthy GFR region.

CONCLUSIONS

The new Q(height)-eGFR equation serves as an excellent screening tool for kidney disease in 1-25-year-old children, adolescents and young adults.

The reproducibility of measurements of differential renal function in paediatric 99mTc-MAG3 renography

OBJECTIVES

The aims of this study were to establish the reproducibility of estimates of differential renal function (DRF) obtained using the software supplied by different vendors, assess the effects of age, glomerular filtration rate (GFR) and degree of asymmetry of renal function on reproducibility and ascertain whether the software gives the same estimates of DRF.

METHODS

A stratified sample of 172 renograms covering a wide range of DRF estimates, age and renal function was drawn from an electronic archive containing raw data from 1416 renograms. The renograms were processed by one operator using seven different methods, five times for each method. For each renogram and each method the DRF for the left kidney and difference between the maximum and minimum of the five estimates of DRF were calculated.

RESULTS

There were differences in reproducibility among the seven methods [Friedman analysis of variance, χ(2)(N=172, d.f.=6)=367.0, P=0.0001]. Reproducibility was good with all methods in most children. The appreciable minority in whom reproducibility was not as good tended to be less than 6 months old or had GFRs below 90 ml/min/1.73 m(2) or both. The median of the DRF estimates of the left kidney obtained using the seven methods differed [Friedman analysis of variance, χ(2)(N=172, d.f.=6)=284.7, P<0.0001]. The largest difference between any two methods was 5%.

CONCLUSION

Although reproducibility was good in the majority of children, an appreciable minority showed poor reproducibility, which could impact clinical decision making. It is essential that these studies be identified. This can be done by processing each renogram several times, ideally using different methods. Those with poorer reproducibility tended to be less than 6 months old or to have a low GFR.

Renal dysfunction and elevated blood pressure in long-term childhood cancer survivors

BACKGROUND AND OBJECTIVES

Little is known about renal function and blood pressure (BP) in long-term childhood cancer survivors. This cross-sectional study evaluated prevalence of these outcomes and associated risk factors in long-term childhood cancer survivors at their first visit to a specialized outpatient clinic.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Estimated GFR; percentages of patients with albuminuria, hypomagnesemia, and hypophosphatemia; and BP were assessed in 1442 survivors ≥5 years after diagnosis. Multivariable logistic regression analyses were used to estimate effect of chemotherapy, nephrectomy, and radiation therapy on the different outcomes.

RESULTS

At a median age of 19.3 years (interquartile range, 15.6-24.5 years), 28.1% of all survivors had at least one renal adverse effect or elevated BP. The median time since cancer diagnosis was 12.1 years (interquartile range, 7.8-17.5 years). High BP and albuminuria were most prevalent, at 14.8% and 14.5%, respectively. Sixty-two survivors (4.5%) had an estimated GFR <90 ml/min per 1.73 m(2). Survivors who had undergone nephrectomy had the highest risk for diminished renal function (odds ratio, 8.6; 95% confidence interval [CI], 3.4-21.4). Combined radiation therapy and nephrectomy increased the odds of having elevated BP (odds ratio, 4.92; 95% CI, 2.63-9.19), as did male sex, higher body mass index, and longer time since cancer treatment.

CONCLUSION

Almost 30% of survivors had renal adverse effects or high BP. Therefore, monitoring of renal function in high-risk groups and BP in all survivors may help clinicians detect health problems at an early stage and initiate timely therapy to prevent additional damage.

Updated height- and creatinine-based equation and its validation for estimation of glomerular filtration rate in children from developing countries

BACKGROUND

Since the original Schwartz formula overestimates glomerular filtration rate (GFR), it is proposed that the constant (k) that accounts for the method of creatinine estimation be derived locally. We derived a new k for height (cm)/serum creatinine (mg/dl) (ht/scr) equation by regression analysis.

METHODS

In a cross-sectional observational study, 197 children (2-18 years) with chronic kidney disease (CKD), who underwent reference GFR measurement by plasma clearance of diethylenetriamine pentaacetic acid (dGFR) at a tertiary care hospital, formed the index dataset for deriving the prediction equations for estimating GFR. Serum creatinine was estimated by the kinetic Jaffe method. The prediction equations were validated on a separate cohort of 225 children with CKD.

RESULTS

The median creatinine was 0.7 mg/dl and dGFR was 80.5 (interquartile range 18.1-137.5) ml/min/1.73 m(2). The new k (regression coefficient of height/creatinine) was 0.42 (R(2) = 0.61) and the updated equation was GFR = 0.42 × (ht/scr). Addition of age and mid-arm circumference (MAC) to this equation improved R (2) to 62.3%. Based on the above parameters, the new equation for estimating GFR was GFR (ml/min/1.73 m(2)) = 0.257 × [ht/scr](0.95) × [age (year)](-0.19) × [MAC (cm)](0.397). The two equations performed comparably, with a mean bias <2 ml/min/1.73 m(2). The updated ht/scr equation yielded 74% and 24% estimated GFR values that were within 30% and 10% of the measured dGFR, respectively.

CONCLUSIONS

The updated equation, with a k value of 0.42, provides a reasonably accurate bedside estimate of GFR in children in countries where creatinine is estimated by the kinetic Jaffe method.

Long-term risk of CKD in children surviving episodes of acute kidney injury in the intensive care unit: a prospective cohort study

BACKGROUND

The development of standardized acute kidney injury (AKI) definitions has allowed for a better understanding of AKI epidemiology, but the long-term renal outcomes of AKI in the pediatric critical care setting have not been well established. This study was designed to: (1) determine the incidence of chronic kidney disease (CKD) in children 1-3 years after an episode of AKI at a tertiary-care pediatric intensive care unit (ICU), (2) identify the proportion of patients at risk of CKD, and (3) compare ICU admission characteristics in those with and without CKD.

DESIGN

Prospective cohort study.

SETTING & PARTICIPANTS

Patients admitted to the British Columbia Children's Hospital pediatric ICU from 2006-2008 with AKI, as defined by AKI Network (AKIN) criteria. Surviving patients, most with short-term recovery from their AKI, were assessed at 1, 2, or 3 years after AKI.

PREDICTORS

Severity of AKI as defined by AKIN and several ICU admission characteristics, including demographics, diagnosis, severity of illness, and ventilation data.

OUTCOMES & MEASUREMENTS

CKD was defined as the presence of albuminuria and/or glomerular filtration rate (GFR) < 60 mL/min/1.73 m2. Being at risk of CKD was defined as having a mildly decreased GFR (60-90 mL/min/1.73 m2), hypertension, and/or hyperfiltration (GFR ≥ 150 mL/min/1.73 m2).

RESULTS

The proportion of patients with AKI stages 1, 2, and 3 were 44 of 126 (35%), 47 of 126 (37%), and 35 of 126 (28%), respectively. The number of patients with CKD 1-3 years after AKI was 13 of 126 (10.3% overall; 2 of 44 [4.5%] with stage 1, 5 of 47 [10.6%] with stage 2, and 6 of 35 [17.1%] with stage 3; P = 0.2). In addition, 59 of 126 (46.8%) patients were identified as being at risk of CKD.

LIMITATIONS

Several patients identified with AKI were lost to follow-up, with the potential of underestimating the incidence of CKD.

CONCLUSIONS

In tertiary-care pediatric ICU patients, ∼10% develop CKD 1-3 years after AKI. The burden of CKD in this population may be higher with further follow-up because several patients were identified as being at risk of CKD. Regardless of the severity of AKI, all pediatric ICU patients should be monitored regularly for long-term kidney damage.

Implications for kidney disease in obese children and adolescents

Increasing attention has been focused on the implications of obesity in adults on the development of kidney disease, but data on the obese pediatric population are lacking. The aim of this study was to investigate whether changes in various renal function indexes/markers, as expressed by the glomerular filtration rate [GFR, as estimated by the Schwartz formula (eGFR)], serum cystatin C (CysC) level, albumin excretion rate (AER), and modifications in nitric oxide (NO; an important modulator of renal function and morphology), urinary isoprostanes (markers of oxidative stress), and blood pressure (BP), can be detected in obese children and adolescents when compared to normal weight controls. Blood and urinary samples were collected to evaluate markers of renal function, serum and urinary NO, and urinary isoprostanes in 107 obese Caucasian subjects and 50 controls. Ambulatory BP monitoring (ABPM) was performed in all cases. Obesity was expressed by the body mass index standard deviation score (SDS-BMI), and insulin resistance by the homeostasis model assessment of insulin resistance (HOMA-IR). CysC and eGFR did not significantly differ between the two groups; AER was increased in obese children. CysC and GFR were related to HOMA-IR, and AER was related to HOMA-IR and SDS-BMI. Obese subjects had reduced NO levels and increased urinary isoprostanes and BP measurements; all three parameters were related to SDS-BMI and insulin resistance. ABPM showed an increased incidence of hypertension and non-dipping in the obese group. Based on our comparison of obese and nonobese children, we conclude that renal involvement is not an early clinically evident manifestation of adiposity in childhood, since no overt changes in eGFR and only a mild albuminuria were detected. A longer exposure to obesity is probably needed before renal function impairment appears.

Acute kidney injury in childhood: should we be worried about progression to CKD?

While emerging evidence indicates that the incidence of both acute kidney injury (AKI) and chronic kidney disease (CKD) in children is rising and that the etiologies are dramatically changing, relatively little is currently known regarding the potential for transition from AKI to CKD. Major barriers to assessing for a potential AKI to CKD link have included lack of a standard pediatric AKI definition, narrow focus only on children with AKI who receive renal replacement therapy, and reliance on serum creatinine as the main biomarker to detect and diagnose AKI and CKD. Recent data have validated a multi-dimensional AKI classification system for children and have suggested chronic kidney sequelae in pediatric populations with AKI or at risk for AKI. In addition, a number of novel AKI biomarkers are being rigorously validated as early indicators of incipient CKD. Our goals for this article are to (1) review the recent changes in pediatric AKI and CKD epidemiology, (2) explore the evidence for a potential AKI to CKD link, and (3) propose new clinical and research paradigms to better elucidate the progression from AKI to CKD.

Estimating glomerular filtration rate in children at serial follow-up when height is unknown

BACKGROUND AND OBJECTIVES

Estimation of GFR in children from serum creatinine measures in regional databases is limited by a lack of height data. Furthermore, the ability of GFR estimating equations to quantify changes in GFR over time is unknown. Two methods of estimating GFR when height is unknown and the ability of several GFR equations to quantify GFR changes over time were evaluated.

DESIGN, SETTING, PARTICIPANTS & MEASUREMENTS

This retrospective study included 195 children (mean age 11.9 ± 4.6 years, GFR = 78.8 ± 34.5) who underwent iothalamate GFR, serum creatinine, and height measurements; 93 children underwent a second GFR measurement and 47 a third GFR measurement. Four equations were evaluated for bias and precision and for quantifying GFR change over time: (1) Schwartz, using measured height; (2) Schwartz, using estimated height (based on previous height percentile); (3) a locally derived modification of a previously derived height-independent equation.

RESULTS

The Schwartz (measured height) displayed the least bias (-2 to +7%), followed by the modified height-independent equation and Schwartz (estimated height). All equations were imprecise. All equations performed similarly at capturing change in measured GFR over time, with no significant difference between estimated and measured GFR percentage change over time. The height-estimated Schwartz formula performed similarly to the height-measured Schwartz in all aspects of equation performance.

CONCLUSIONS

Pediatric GFR follow-up studies may be possible using height-independent equations. Estimating height from prior height measurements enhances GFR estimation when height is unknown. These findings will hopefully help advance future pediatric renal function database studies.

On the relationship between glomerular filtration rate and serum creatinine in children

The Schwartz formula (eGFR = kL/Scr, with k = 0.55) to determine the estimated glomerular filtration rate (eGFR) in children with chronic kidney disease (CKD), based on length (L) and serum creatinine (Scr) has recently been updated for enzymatic serum creatinine concentrations, resulting in k = 0.413. Based on a meta-analysis, we evaluated the validity of this updated equation and other published equations for healthy children. This is the first time that publicly available data for healthy children of uncorrected and body surface area (BSA)-corrected median GFR have been combined with median serum creatinine values and median lengths and weights from different sources in the literature to evaluate several statistical models to estimate GFR in children. For enzymatic serum creatinine, we show that the simple model for uncorrected GFR (uGFR = k'L(3)/Scr, with k' = 1.32 x 10(-5)) and the BSA-corrected GFR (cGFR = kL/Scr, analogous to the Schwartz formula), with an important age-dependent adaptation for k (k = 0.0414 x 1n (Age) + 0.3018), correlate extremely well with chromium-51-ethylenediamine tetra-acetic acid ((51)Cr-EDTA) data for children between 1 month and 14 years of age. With this age-dependent modification for k, presented here, the simple bedside calculation tool derived by Schwartz can be used for screening all children for CKD. When height information is not available, the Lund-Malmö equation is an excellent alternative.

Determinants of eGFR at start of renal replacement therapy in paediatric patients

BACKGROUND

Few studies have investigated the determinants of glomerular filtration rate (GFR) in paediatric patients starting on dialysis or with a transplant.

METHODS

Data were collected as part of the European Society of Paediatric Nephrology/European Renal Association-European Dialysis and Transplant Association registry from 14 European countries and referred to incident paediatric patients starting on renal replacement therapy (RRT) between 2002 and 2007 under the age of 18 years. Estimated glomerular filtration rate (eGFR) was calculated using the Schwartz formula. Data were adjusted for age, gender, treatment modality at start, primary cause of renal failure (PRD) and regions in Europe (eGFR(adj)).

RESULTS

Median eGFR in the 938 patients starting RRT was 10.4 mL/min/1.73 m(2) (5th and 95th percentile: 4.0-26.9). Twenty-six patients (2.8%), mainly infants with Finnish-type nephropathy, started with eGFR levels >50 mL/min/1.73 m(2). Younger age, female gender, starting on dialysis and having a short time between the first visit to a paediatric nephrologist (PN) and start of RRT were associated with lower eGFR at start of RRT. Gender differences were only present during adolescent age and disappeared when using the same K value for both genders. The various PRDs showed large differences in the rate of decline in eGFR between the first visit to a PN and start of RRT; however, this did not result in differences in eGFR(adj) at start of RRT.

CONCLUSIONS

The main determinants of eGFR at start of RRT were age, gender, treatment modality at start, and the time between the first visit to a PN and start of RRT. Research is needed to determine the consequences of these differences.

Metabolic syndrome risk factors and estimated glomerular filtration rate among children and adolescents

The aim of this study was to seek the possible relationship between estimated glomerular filtration rate (e-GFR) and anthropometric indexes, lipids, insulin sensitivity, and metabolic syndrome risk factors among healthy children and adolescents. Sufficient evidence suggest that obesity is related with a novel form of glomerulopathy named obesity-related glomerulopathy (ORG) among adults, children, and adolescents. Glomerular filtration rate was estimated from serum creatinine in 166 healthy children and adolescents [79 males, 87 females; age 10.6 +/- 3.3 (3-18) years]. Anthropometric indexes and systolic and diastolic blood pressure were measured. Fasting insulin, glucose, creatinine, uric acid, total cholesterol, high-density lipoprotein (HDL)-cholesterol, low-density lipoprotein (LDL)-cholesterol, and triglycerides were estimated. Insulin sensitivity was estimated from known formulas. The presence of certain metabolic syndrome risk factors was checked among the studied population. Boys showed higher e-GFR rates than girls (f = 8.49, p = 0.004). We found a strong positive correlation between e-GFR and body weight (r = 0.415), body mass index (BMI) (r = 0.28), waist circumference (r = 0.419), hip circumference (r = 0.364), birth weight (r = 0.164), systolic blood pressure (SBP) (r = 0.305), and mean arterial pressure (MAP) (r = 0.207). A negative correlation was found between e-GFR and fasting glucose (r = -0.19), total cholesterol (r = -0.27) and LDL-cholesterol (r = -0.26). Clustering of metabolic syndrome risk factors among certain individuals was correlated with higher e-GFR rates (f = 3.606, p = 0.007). The results of this study suggest that gender, anthropometric indexes, and SBP are strong positive determinants of e-GFR among children and adolescents. Waist circumference is the most powerful determinant of e-GFR. Fasting glucose and lipid abnormalities are negative determinants of e-GFR among the studied population. Clustering of metabolic syndrome risk factors is coupled with higher e-GFR rates.

Screening for kidney disease in children on World Kidney Day in Jalisco, Mexico

World Kidney Day (WKD) is intended to raise awareness and increase detection of chronic kidney disease (CKD), but most emphasis is placed on adults rather than children. We examined yield of screening for CKD and hypertension among poor children in Mexico. On WKD (2006, 2007), children (age < 18 years) without known CKD were invited to participate at two screening stations. We measured body mass index (BMI), blood pressure, and serum creatinine, and performed dipstick urinalysis. The Schwartz equation was used to estimate glomerular filtration rate (GFR; reduced GFR defined as < 60 ml/min per 1.73 m(2)). Proteinuria and hematuria were defined by a reading of >or= 1+ protein or blood on dipstick. Hypertension was defined by gender, age, and height-specific norms. In total, 240 children were screened (mean age 8.9 +/- 4.1 years; 44.2% male). Proteinuria and hematuria were detected in 38 (16.1%) and 41 (17.5%), respectively; 15% had BMI > 95th percentile for age. Reduced GFR was detected in four (1.7%) individuals. Systolic hypertension was more prevalent in younger children (age 0-8 years, 19.6%; age 9-13 years, 7.1%; age 14-17 years, 5.3%) suggesting a possible white-coat effect. Hematuria, proteinuria, hypertension and obesity were frequently detected among children in a community based screening program in Mexico. This form of screening might be useful in identifying children with CKD and hypertension in developing nations.

Determination and modelling of clinical laboratory data of healthy individuals and patients with end-stage renal failure

The analyses of 18 biochemical parameters (alanine aminotransferase, albumin, aspartate aminotransferase, calcium, cholesterol, chloride, creatinine, iron, glucose, γ- glutamyl transferase, alkaline phosphatase, phosphorus, potassium, sodium, total protein, triglycerides, uric acid, and urea nitrogen) were performed for 166 healthy individuals and 108 patients with end-stage renal failure (ESRF). The application of cluster analysis proved that there were points of similarity among all 18 biochemical parameters that formed major groups; these groups corresponded to the authors’ assumption of the existence of several overall patterns of biochemical parameters that may be termed “enzyme-specific”; “general health indicator”; “major component excretion”; “blood-specific indicator”; and “protein-specific”. These patterns also appear in the subsets of males and females that were obtained by separation of the general dataset. In addition, the performance of factor analysis similarly proved the validity of this assumption. This projection and modelling method indicated the existence of seven latent factors, which explained 70.05% of the total variance in the system for healthy individuals and more than 72% of the total variance in the system for patients with ESRF. All these results support the probability that a general health indicator could be constructed by taking into account the existing classification groups in the list of biochemical parameters.

New equations to estimate GFR in children with CKD

The Schwartz formula was devised in the mid-1970s to estimate GFR in children. Recent data suggest that this formula currently overestimates GFR as measured by plasma disappearance of iohexol, likely a result of a change in methods used to measure creatinine. Here, we developed equations to estimate GFR using data from the baseline visits of 349 children (aged 1 to 16 yr) in the Chronic Kidney Disease in Children (CKiD) cohort. Median iohexol-GFR (iGFR) was 41.3 ml/min per 1.73 m(2) (interquartile range 32.0 to 51.7), and median serum creatinine was 1.3 mg/dl. We performed linear regression analyses assessing precision, goodness of fit, and accuracy to develop improvements in the GFR estimating formula, which was based on height, serum creatinine, cystatin C, blood urea nitrogen, and gender. The best equation was: GFR(ml/min per 1.73 m(2))=39.1[height (m)/Scr (mg/dl)](0.516) x [1.8/cystatin C (mg/L)](0.294)[30/BUN (mg/dl)](0.169)[1.099](male)[height (m)/1.4](0.188). This formula yielded 87.7% of estimated GFR within 30% of the iGFR, and 45.6% within 10%. In a test set of 168 CKiD patients at 1 yr of follow-up, this formula compared favorably with previously published estimating equations for children. Furthermore, with height measured in cm, a bedside calculation of 0.413*(height/serum creatinine), provides a good approximation to the estimated GFR formula. Additional studies of children with higher GFR are needed to validate these formulas for use in screening all children for CKD.

Ascertainment and epidemiology of acute kidney injury varies with definition interpretation

BACKGROUND AND OBJECTIVES

Differences in defining acute kidney injury (AKI) may impact incidence ascertainment. We assessed the effects of different AKI definition interpretation methods on epidemiology ascertainment.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Two groups were studied at Texas Children's Hospital, Houston, Texas: 150 critically ill children (prospective) and 254 noncritically ill, hospitalized children receiving aminoglycosides (retrospective). SCr was collected for 14 d in the prospective study and 21 d in the retrospective study. Children with known baseline serum creatinine (bSCr) were classified by the pediatric Risk, Injury, Failure, Loss, End-Stage Kidney Disease (pRIFLE) AKI definition using SCr change (pRIFLE(DeltaSCr)), estimated creatinine clearance (eCCl) change (pRIFLE(DeltaCCl)), and the Acute Kidney Injury Network (AKIN) definition. In subjects without known bSCr, bSCR was estimated as eCCl = 100 (eCCl(100)) and 120 ml/min per 1.73 m(2) (eCCl(120)), admission SCr (AdmSCr) and lower/upper normative values (NormsMin, NormsMax). The differential impact of each AKI definition interpretation on incidence estimation and severity distribution was evaluated.

RESULTS

pRIFLE(DeltaSCr) and AKIN led to identical AKI distributions. pRIFLE(DeltaCCl) resulted in 14.5% (critically ill) and 11% (noncritical) more patients diagnosed with AKI compared to other methods (P 0.05). Different bSCr estimates led to differences in AKI incidence, from 12% (AdmSCr) to 87.8% (NormsMin) (P 0.05) in the critically ill group and from 4.6% (eCCl(100)) to 43.1% (NormsMin) (P 0.05) in the noncritical group.

CONCLUSIONS

AKI definition variation causes interstudy heterogeneity. AKI definition should be standardized so that results can be compared across studies.

Monitoring renal function and limitations of renal function tests

Chronic kidney disease (CKD) is a world-wide public health problem, with adverse outcomes of kidney failure, cardiovascular disease, and premature death. The National Kidney Foundation, through its Kidney Disease Quality Outcome Initiative (K/DOQI) and other National institutions, recommend glomerular filtration rate (GFR) estimates for the definition, classification, screening, and monitoring of CKD. Prediction equations based on serum creatinine values were chosen both for adults (Cockcroft-Gault [C-G] and Modification of Diet in Renal Disease [MDRD] study equations) and for children (Schwartz and Counahan-Barratt equations). This review aims to evaluate from recent literature the clinical efficiency and relevance of these equations in terms of bias, precision, and reproducibility in different specific indications (eg, screening CKD, assessment of disease progression, or therapy efficacy) in different populations. Because these prediction equations based on serum creatinine have limitations, especially in the normal or near-normal GFR range, kidney transplant recipients, and pediatric populations, other prediction equations based on serum cystatin C value were also considered as possibly more sensitive GFR surrogate markers. Recent guidelines state that the cystatin C-based prediction equation cannot be recommended for use in clinical practice. With prediction equations based on serum creatinine, the National Kidney Disease Education Program (NKDEP) recommendations are to report a numerical estimate in round numbers only for GFR values <60 mL/min per 1.73 m(2). The MDRD equation generally outperforms the C-G equation but may still have a high level of bias, depending on creatinine assay calibration, and low precision with, at best, approximately 80% of estimated GFR in the "accuracy range" of 70-130% of the measured GFR value, even in patients with known CKD. According to Kidney Disease Improving Global Outcomes (KDIGO) recommendations, many indications remain for GFR measurements using a clearance method. In that context, it should be recalled that radiolabeled-tracer plasma or urinary clearance methods, are safe, simple, accurate and reproducible.

Evaluation of activity, chronicity and tubulointerstitial indices for childhood lupus nephritis

Few data exist on use of the National Institutes of Health (NIH) activity index (AI) and chronicity index (CI) in childhood lupus nephritis (LN). A tubulointerstitial activity index (TIAI) has been derived but not validated. We evaluated clinicopathologic correlations of the AI, CI and TIAI in children with LN who had undergone initial renal biopsy (n=25, age 12.4+/-2.7 years, biopsy 1) and 1 year after treatment (n=15, biopsy 2). The TIAI correlated with the AI at biopsy 1 (r=0.76, P=0.001) and biopsy 2 (r=0.52, P=0.05), but not with CI scores. Mean AI and CI scores changed substantially from biopsy 1 to biopsy 2 (P<0.05), but TIAI scores did not. Higher AI and TIAI scores correlated with proteinuria at both biopsies (r=0.51-0.76, P<0.05); CI scores correlated with estimated creatinine clearance (r=0.46-0.58, P<0.05). Improved AI score from biopsy 1 to biopsy 2 was associated with decrease in proteinuria. These results suggest that the AI and CI are useful in childhood LN. The TIAI may be a valid measure to evaluate the tubulointerstitium, but research is needed to define its responsiveness to change with therapy.

Bias and precision of estimated glomerular filtration rate in children

Determining true glomerular filtration rate (GFR) using an exogenous marker is time-consuming and cumbersome. Therefore, creatinine-based estimates of GFR are used. Recent papers using new population-specific/local parameters in their prediction equations, standardizing creatinine determination or adding other endogenous surrogate markers of GFR, like cystatin C, could demonstrate an improvement of bias inherent in the results of the prediction equations. Precision, however, is still poor. Currently, we have to accept a precision (as defined in the so-called Bland-Altman plot) of +/-20% in adults and +/-30-40% in children. This problem of poor precision/uncertainty is especially bothering in the higher, near normal GFR range. Caution should be exercised when applying prediction equations in individuals in need of an accurate GFR determination. In that case, a real clearance procedure has to be performed. In the long run, the true clearance procedure should be simplified using new exogenous GFR markers and developing new devices, allowing GFR measurements to be performed, for example, transcutaneously. Such a procedure would be more acceptable for both patients and physicians.