Towards a biomarker panel for the assessment of AKI in children receiving intensive care

Urinary tissue inhibitor of metalloproteinase-2 as an early predictor for acute kidney injury in critically ill children

Objectives

Acute kidney injury (AKI) is one of the most devastating complications of critical illness in children. Serum creatinine (Scr) is considered the gold standard for AKI diagnosis yet noted to be late and inaccurate. This raises the need for an early and accurate biochemical parameter for the early detection of AKI. This research aimed to explore the role of urinary tissue inhibitor metalloproteinase 2 (TIMP-2) in the early prediction of AKI, compared to standard biomarkers, in critically ill children admitted to pediatric intensive care unit (PICU). Urine TIMP2 was previously explored in multiple adult studies and showed promising results; however, the study of its role in pediatric population was limited.

Methods

This study was a prospective cohort study including 42 critically ill children who are at increased risk of AKI. Cases were recruited from the PICU in the Children's Hospital of Ain-Shams University, Cairo - Egypt over 10 months' duration. Urine samples were collected to measure urinary TIMP-2 and blood samples were taken to measure the levels of Scr, creatinine clearance, and blood urea nitrogen. Urine output in 24 h was also calculated.

Results

Urinary TIMP-2 showed considerably higher levels in AKI compared to non-AKI patients as early as day 1, whereas increased levels of Scr and decreased urine output were noticed later (day 3 and day 5, respectively). A notable correlation existed between TIMP-2 at day 1 and creatinine at day 3.

Conclusion

The present study revealed that urinary TIMP-2 could have an important role in the early prediction of AKI before the increase in Scr and more deterioration in kidney functions.

Optimizing Vancomycin Therapy in Critically Ill Children: A Population Pharmacokinetics Study to Inform Vancomycin Area under the Curve Estimation Using Novel Biomarkers

Area under the curve (AUC)-directed vancomycin therapy is recommended, but Bayesian AUC estimation in critically ill children is difficult due to inadequate methods for estimating kidney function. We prospectively enrolled 50 critically ill children receiving IV vancomycin for suspected infection and divided them into model training (n = 30) and testing (n = 20) groups. We performed nonparametric population PK modeling in the training group using Pmetrics, evaluating novel urinary and plasma kidney biomarkers as covariates on vancomycin clearance. In this group, a two-compartment model best described the data. During covariate testing, cystatin C-based estimated glomerular filtration rate (eGFR) and urinary neutrophil gelatinase-associated lipocalin (NGAL; full model) improved model likelihood when included as covariates on clearance. We then used multiple-model optimization to define the optimal sampling times to estimate AUC24 for each subject in the model testing group and compared the Bayesian posterior AUC24 to AUC24 calculated using noncompartmental analysis from all measured concentrations for each subject. Our full model provided accurate and precise estimates of vancomycin AUC (bias 2.3%, imprecision 6.2%). However, AUC prediction was similar when using reduced models with only cystatin C-based eGFR (bias 1.8%, imprecision 7.0%) or creatinine-based eGFR (bias -2.4%, imprecision 6.2%) as covariates on clearance. All three model(s) facilitated accurate and precise estimation of vancomycin AUC in critically ill children.

Early diagnosis of kidney injury in a paediatric population: a prospective cohort study (E-DRIP STUDY)

BACKGROUND

Renal Angina Index (RAI) is a bedside tool for risk stratification of patients to predict acute kidney injury (AKI). Kidney biomarkers are better indicators of real-time injury and give us lead time for diagnosing impending AKI.

METHODS

We enrolled consecutive children aged 2 months-14 years admitted to a tertiary hospital in northern India over 2 years. RAI was calculated on day 0 (D0) and urinary (u) and plasma (p) neutrophil gelatinase-associated lipocalin (NGAL) were measured within 6 h of admission. Children were followed for the development of severe AKI on day 3 (D3) using Kidney Disease Improving Global Outcomes criteria to define and stage AKI.

RESULTS

Of the 253 children enrolled and analysed, 44 (17.4%) developed D3-AKI (stage 1 in 52.2%, stage 2 in 20.5% and stage 3 in 27.3%). Renal angina (RAI ≥ 8) on D0 was present in 66.7% children who developed stage 2/3 D3-AKI vs. 43.5% in children who did not develop D3-AKI /stage 1 AKI (p = 0.065). Area under ROC (AUROC) curve for D0-RAI to predict D3-severe-AKI was 0.66 (95% CI, 0.55-0.77). AUROC curve for uNGAL and pNGAL to predict D3-severe-AKI was 0.62 (95% CI, 0.50-0.74) and 0.48 (95% CI, 0.35-0.61), respectively. The severe AKI group had greater requirement of ventilation and inotropic support with mortality being thrice higher compared to the non-AKI group.

CONCLUSION

RAI ≥ 8 and uNGAL had a high negative predictive value but low sensitivity for predicting D3-severe-AKI. pNGAL had a poor predictive value for D3-severe-AKI. A higher resolution version of the Graphical abstract is available as Supplementary information.

Neutrophil Gelatinase-Associated Lipocalin (NGAL) in kidney injury- A systematic review

BACKGROUND

Neutrophil Gelatinase Associated Lipocalin (NGAL) is a secretory protein of neutrophils that can be found both in plasma and urine. Previous works have demonstrated a valuable marker for the early detection of acute kidney injury. In this systematic review, we aimed to assess whether NGAL could be helpful in the diagnosis and prognosis of systemic diseases with kidney involvement.

METHODS

MEDLINE, PubMed, and EMBASE databases were searched for NGAL, described as a human biomarker for diseases (total: 1690). Specifically, included studies describing the use of NGAL for determining kidney injury outcomes and other conditions associated with kidney dysfunction, including cardiovascular diseases, cardiac surgery, and critically ill systemic disorders.

RESULTS

A total of 24 validated studies were included in the systemic review after applying the exclusion criteria. In all these studies, NGAL appeared to have a predictive value irrespective of age, from newborn to 78 years. The results indicate that NGAL levels can accurately predict the outcome and severity of acute kidney injury occur in several disease processes, including contrast-induced AKI during cardiac surgery, kidney transplant rejection, chronic heart failure, and systemic inflammation in critically ill patients, even though the significance of NGAL is highly variable across studies. Very high plasma NGAL levels were observed in the patients before the acute rejection of the kidney, indicating the prognostic potential of the NGAL. Specifically, the assays conducted before 72 hrs provided a significant predictive value.

CONCLUSION

Urinary and serum NGAL appears to be an independent predictor of not only kidney complications but also cardiovascular and liver-related diseases. The kidney is also involved in pathogenesis.

Biomarkers of acute kidney injury in pediatric cardiac surgery

Acute kidney injury (AKI) is characterized by a sudden decrease in kidney function. Children with congenital heart disease are a special group at risk of developing AKI. We performed a systematic review of the literature to search for studies reporting the usefulness of novel urine, serum, and plasma biomarkers in the diagnosis and progression of AKI and their association with clinical outcomes in children undergoing pediatric cardiac surgery. In thirty studies, we analyzed the capacity to predict AKI and poor outcomes of five biomarkers: Cystatin C, Neutrophil gelatinase-associated lipocalin, Interleukin-18, Kidney injury molecule-1, and Liver fatty acid-binding protein. In conclusion, we suggest the need for further meta-analyses with the availability of additional studies.

Proenkephalin as a new biomarker for pediatric acute kidney injury - reference values and performance in children under one year of age

Objectives Acute kidney injury (AKI) is common in critically ill children, but current biomarkers are suboptimal. Proenkephalin A 119-159 (PENK) is a promising new biomarker for AKI in adults, but pediatric data is lacking. We determined PENK reference intervals for healthy children, crucial for clinical implementation, and explored concentrations in critically ill infants aged under 1 year. Methods Observational cohort study in healthy infants and critically ill children aged 0-1 years. Reference values were determined using generalized additive models. Plasma PENK concentrations between healthy children and critically ill children with and without AKI, were compared using linear mixed modelling. The performance of PENK as AKI biomarker was compared to cystatin C (CysC) and β-trace protein (BTP) using receiver-operating-characteristic (ROC) analysis. Results PENK concentrations in 100 healthy infants were stable during the first year of life (median 517.3 pmol/L). Median PENK concentrations in 91 critically ill children, were significantly higher in those with AKI (n=40) (KDIGO Stage 1 507.9 pmol/L, Stage 2 704.0 pmol/L, Stage 3 930.5 pmol/L) than non-AKI patients (n=51, 432.2 pmol/L) (p < 0.001). PENK appeared to relate better to AKI diagnosis than CysC and BTP (AUROC PENK 0.858, CysC 0.770 and BTP 0.711) in the first 24 h after recruitment. Conclusions PENK reference values are much higher in young infants than adults, but clearly discriminate between children with and without AKI, with comparable or better performance than CysC and BTP. Our results illustrate the importance of establishing age-normalized reference values and indicate PENK as a promising pediatric AKI biomarker.

Ability of different assay platforms to measure renal biomarker concentrations during ischaemia-reperfusion acute kidney injury in dogs

Several protein biomarkers have been shown to be useful for the early diagnosis of acute kidney injury (AKI) in animals and people. Multiplex assays for measurement of a panel of renal biomarkers in canine samples have recently become available. This study compared the use of two such assays, versus previously validated ELISAs, to measure five biomarkers in canine samples during ischaemia-reperfusion (IR) AKI. Blood and urine was collected from six male anaesthetised greyhounds that underwent 1-h of renal ischaemia (severe hypotension induced by acute haemorrhage) and 2-h of reperfusion (intravenous fluid resuscitation). Histology confirmed presence of acute tubular injury at 2 h of reperfusion. Concentrations of clusterin, cystatin C, kidney-injury molecule 1 (KIM-1), monocyte chemoattractant protein 1, and neutrophil gelatinase-associated lipocalin (NGAL) at baseline and following IR, measured by two different multiplex assays and previously-validated single analyte immunoassays, were compared. Only NGAL was significantly elevated following IR with all assays investigated. Whether concentrations of the other four biomarkers were significantly increased following IR depended on the assay used. Concentrations of cystatin C and KIM-1 measured with the multiplex assays were of a vast magnitude lower than those measured with the corresponding single analyte ELISAs. We conclude that further validation is required before these assays can reliably be used to measure AKI biomarkers in canine samples.

The Epidemiology and Management of Pediatric AKI in Asia

Because of the lack of early recognition and referral, the incidence of pediatric acute kidney injury (AKI) in Asia still is underestimated. Although each diagnostic criteria has its own merits, the Kidney Disease Improving Global Outcomes classification now is widely accepted. In Asia, the spectrum of pediatric AKI is wide-ranging, from pediatric AKI in highly sophisticated tertiary-care pediatric intensive care units in resource-rich regions due to advanced procedures such as transplantation, cardiac surgery, and other hospital-acquired causes, to primary care preventable causes, such as infectious diseases, snakebite, and so forth in rural parts of the developing world. The development and application of novel biomarkers, concepts such as the Renal Angina Index and advanced renal replacement therapy have revolutionized the era of treating AKI, but the cost and feasibility are the key determinants, especially in rural areas. In view of availability and expenses, peritoneal dialysis should be the first choice in less-developed areas, however, because of various barriers, it still needs more effort. Effective educational steps to both medical carers and families are needed urgently.

Accuracy of Urine Kidney Injury Molecule-1 in Predicting Acute Kidney Injury in Children; a Systematic Review and Meta-Analysis

INTRODUCTION

There is considerable controversy on the accuracy of Kidney Injury Molecule-1 (KIM-1) in prediction of acute kidney injury (AKI) in children. Therefore, the present study intends to provide a systematic review and meta-analysis of the value of this biomarker in predicting AKI in children.

METHODS

An extensive search was performed on the Medline, Embase, Scopus and Web of Science databases by the end of 2019. Cohort and case-control studies on children were included. Urinary KIM-1 levels were compared between AKI and non-AKI groups. Findings were reported as an overall standardized mean difference (SMD) with a 95% confidence interval (CI). Also, the overall area under the receiver operating characteristic (ROC) curve (AUC) of KIM-1 in predicting AKI in children was calculated.

RESULTS

Data from 13 articles were included. Urinary KIM-1 levels in children with stage 1 AKI were higher than the non-AKI group only when assessed within the first 12 hours after admission (SMD = 0.95; 95% CI: 0.07 to 1.84; p = 0.034). However, urinary KIM-1 levels in children with stage 2-3 AKI were significantly higher than non-AKI children (p <0.01) at all times. The AUC of urinary KIM-1 in predicting AKI in children was 0.69 (95% CI: 0.62 to 0.77).

CONCLUSION

Based on the available evidence, KIM-1 seems to have moderate value in predicting AKI in children. Since previous meta-analyses have provided other urinary and serum biomarkers that have better discriminatory accuracy than KIM-1, so it had better not to use KIM-1 in predicting AKI in children.

Early Diagnosis and Prognostic Value of Acute Kidney Injury in Critically Ill Patients

Background and objectives: In hospitalized children, acute kidney injury (AKI) remains to be a frequent and serious condition, associated with increased patient mortality and morbidity. Identifying early biomarkers of AKI and patient groups at the risk of developing AKI is of crucial importance in current clinical practice. Specific human protein urinary neutrophil gelatinase-associated lipocalin (uNGAL) and interleukin 18 (uIL-18) levels have been reported to peak specifically at the early stages of AKI before a rise in serum creatinine (sCr). Therefore, the aim of our study was to determine changes in uNGAL and uIL-18 levels among critically ill children and to identify the patient groups at the highest risk of developing AKI. Materials and methods: This single-center prospective observational study included 107 critically ill children aged from 1 month to 18 years, who were treated in the Pediatric Intensive Care Unit (PICU) of Lithuanian University of Health Sciences Hospital Kauno Klinikos from 1 December 2013, to 30 November 2016. The patients were divided into two groups: those who did not develop AKI (Group 1) and those who developed AKI (Group 2). Results: A total of 68 (63.6%) boys and 39 (36.4%) girls were enrolled in the study. The mean age of the patients was 101.30 ± 75.90 months. The mean length of stay in PICU and hospital was 7.91 ± 11.07 and 31.29 ± 39.09 days, respectively. A total of 32 (29.9%) children developed AKI. Of them, 29 (90.6%) cases of AKI were documented within the first three days from admission to hospital. In all cases, AKI was caused by diseases of non-renal origin. There was a significant association between the uNGAL level and AKI between Groups 1 and 2 both on day 1 (p = 0.04) and day 3 (p = 0.018). Differences in uNGAL normalized to creatinine in the urine (uCr) (uNGAL/uCr) between the groups on days 1 and 3 were also statistically significant (p = 0.007 and p = 0.015, respectively). uNGAL was found to be a good prognostic marker. No significant associations between uIL-18 or Uil-18/uCr and development of AKI were found. However, the uIL-18 level of >69.24 pg/mL during the first 24 h was associated with an eightfold greater risk of AKI progression (OR = 8.33, 95% CI = 1.39–49.87, p = 0.023). The AUC for uIL-18 was 73.4% with a sensitivity of 62.59% and a specificity of 83.3%. Age of <20 months, Pediatric Index of Mortality 2 (PIM2) score of >2.5% on admission to the PICU, multiple organ dysfunction syndrome with dysfunction of three and more organ systems, PICU length of stay more than three days, and length of mechanical ventilation of >five days were associated with a greater risk of developing AKI. Conclusions: Significant risk factors for AKI were age of <20 months, PIM2 score of >2.5% on admission to the PICU, multiple organ dysfunction syndrome with dysfunction of 3 and more organ systems, PICU length of stay of more than three days, and length of mechanical ventilation of > five days. uNGAL was identified as a good prognostic marker of AKI. On admission to PICU, uNGAL should be measured within the first three days in patients at the risk of developing AKI. The uIL-18 level on the first day was found to be as a biomarker predicting the progression of AKI.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C measurements for early diagnosis of acute kidney injury in children admitted to PICU

BACKGROUND

Acute kidney injury (AKI) is common in critically ill children with significant mortality and morbidity. Serum creatinine is an insensitive and late biomarker compared to newly proposed AKI biomarkers.

METHODS

Prospective study in pediatric intensive care unit (PICU) over three months to compare between serum cystatin-C (s-Cys-C) and urinary neutrophil gelatinase-associated lipocalin (uNGAL) as AKI biomarkers at multiple time points with pediatric risk, injury, failure, loss, end-stage renal disease (pRIFLE) classification in diagnosing AKI.

RESULTS

Forty children were recruited. Of these 40 children, 22 developed AKI according to pRIFLE criteria. There was no significant difference between AKI and non-AKI in age (P = 0.29). Post cardiac surgery, renal insult was the main cause of AKI (27.3%). There was a twofold increased risk of incident AKI in those patients with high baseline uNGAL at PICU admission and almost a fourfold increased risk in patients with high baseline s-Cys-C at PICU admission. uNGAL levels were highly predictive of AKI during the follow-up period [area under the curve (AUC) = 0.76, 95% confidence interval (CI) 0.61-0.92]. The cutoff point with the highest correctly classified proportion was 223 ng/mL (≥ 12 centiles) which correctly predict 80.0% patients with AKI, with a corresponding sensitivity of 72.7% and a specificity of 89.9%. AUC for s-Cys-C was 0.86 (95% CI 0.75-0.97), and the highest correctly classified proportion was 1009 µg/L (≥ 13 centiles); 75% of patients with AKI, with a corresponding sensitivity of 63.6% and a specificity of 88.9%.

CONCLUSION

uNGAL and s-Cys-C predicts AKI early in critically ill children.

Accuracy of cystatin C in prediction of acute kidney injury in children; serum or urine levels: which one works better? A systematic review and meta-analysis

BACKGROUND

There is still an ongoing discussion on the prognostic value of cystatin C in assessment of kidney function. Accordingly, the present study aimed to conduct a meta-analysis to provide evidence for the prognostic value of this biomarker for acute kidney injury (AKI) in children.

METHODS

An extensive search was performed in electronic databases of Medline, Embase, ISI Web of Science, Cochrane library and Scopus until the end of 2015. Standardized mean difference (SMD) with a 95% of confidence interval (95% CI) and the prognostic performance characteristics of cystatin C in prediction of AKI were assessed. Analyses were stratified based on the sample in which the level of cystatin C was measured (serum vs. urine).

RESULTS

A total of 24 articles were included in the meta-analysis [1948 children (1302 non-AKI children and 645 AKI cases)]. Serum (SMD = 0.96; 95% CI: 0.68-1.24; p < 0.0001) and urine (SMD = 0.54; 95% CI:0.34-0.75; p < 0.0001) levels of cystatin C were significantly higher in children with AKI. Overall area under the curve of serum cystatin C and urine cystatin C in prediction of AKI were 0.83 (95% CI: 0.80-0.86) and 0.85 (95% CI: 0.81-0.88), respectively. The best sensitivity (value = 0.85; 95% CI: 0.78-0.90) and specificity (value = 0.61; 95% CI: 0.48-0.73), were observed for the serum concentration of this protein and in the cut-off points between 0.4-1.0 mg/L.

CONCLUSION

The findings of the present study showed that cystatin C has an acceptable prognostic value for prediction of AKI in children. Since the serum level of cystatin C rises within the first 24 h of admission in patients with AKI, this biomarker can be a suitable alternative for traditional diagnostic measures.

Reference ranges and impact of selected confounders on classic serum and urinary renal markers in neonatal period

PURPOSE

Renal injury in term and pre-term neonates may be an antecedent to chronic kidney disease in the child's further life. The aim of the paper was to compile a reference range for selected serum and urinary renal markers in the neonatal period for full-term (FT) and pre-term (PT) newborns.

MATERIAL AND METHODS

The prospective study included 23 FT infants (birth weight - BW≥2500g and gestational age - GA≥37Hbd) and 32 PT children (BW<2500g and GA<37Hbd) in good general condition, without acute kidney injury (AKI) or sepsis. Between the 4th and 28th DOL, urinary concentrations of the studied renal markers (uCr, uNa, uOsm) were determined on a daily basis, while serum creatinine (SCr) was assessed minimum every 48-72h.

RESULTS

The mean GA and BW of the FT and PT infants were respectively as follows: 38.5±1.7Hbd; 3433±495.2g and 32.7±2.6Hbd; 1836.7±419.8g. For serum glomerular (SCr, eGFR) and tubular markers (FENa, RFI), the median values with normal ranges were compiled. For urinary renal markers (uCr, uNa, uOsm) and those values standardized for kg of body weight, percentile tables for 4-28DOL were elaborated.

CONCLUSIONS

The study has resulted in determining the normal ranges of serum glomerular and tubular renal markers, as well as percentile tables of selected urinary renal parameters during the neonatal period. The percentile tables may prove to be helpful for further standardization of other urinary parameters per urinary creatinine in neonatal population.

Stop adding insult to injury-identifying and managing risk factors for the progression of acute kidney injury in children

Acute kidney injury (AKI) is common in children admitted to hospital. Whilst some recover normal kidney function following an acute kidney insult, a significant proportion experience long-term sequelae. The aim of this review is to summarize current understanding of the processes that can lead to sequelae following AKI. Kidney injury, repair, recovery and progression are described. Risk factors for progression are outlined, and potential strategies to stratify the risk of progression in children with AKI are discussed. Clinical management priorities to minimize sequelae are suggested. Looking ahead, novel therapeutic targets are discussed with the potential to accelerate adaptive repair and ameliorate the progression and sequelae of AKI in the future.

Recent developments in the detection and management of acute kidney injury

Acute kidney injury (AKI) is a common condition in children admitted to hospital and existing serum and urine biomarkers are insensitive. There have been significant developments in stratifying the risk of AKI in children and also in the identification of new AKI biomarkers. Risk stratification coupled with a panel of AKI biomarkers will improve future detection of AKI, however, paediatric validation studies in mixed patient cohorts are required. The principles of effective management rely on treating the underlying cause and preventing secondary AKI by the appropriate use of fluids and medication. Further therapeutic innovation will depend on improving our understanding of the basic mechanisms underlying AKI in children.

THE IMPACT OF FIXED CONCENTRATIONS SEDATION INFUSIONS ON FLUID OVERLOAD IN CRITICALLY ILL CHILDREN

INTRODUCTION

Fluid overload of 10% at 48 hrs (100 ml/kg additional fluid) is strongly associated with morbidity in critically ill children.1 Contributors include fluid resuscitation, acute kidney injury, and administration of intravenous drugs. Acute Kidney Injury has been observed to be more prevalent in infants.2 Drug infusions are historically prepared according to bodyweight to run at large volumes to facilitate end-of-bed calculation and administration. We report the impact of using standardised concentrations on fluid overload in critically ill children in a tertiary general PICU.

METHODS

Administration of sedation infusions was prospectively documented using purposive sampling until a population-representative sample for age and weight was obtained. Infusion volumes were calculated in ml/kg/day for different weight groups - 0-5 kg, 5-20 kg and <20 kg - and compared with equivalent volumes for weight-based infusions.

RESULTS

33 patients received sedation infusions over a 5 week period. Overall drug volumes were reduced by 50.3%(41.3 to 58.7%) from 5.19 ml/kg to 2.65 ml/kg. Greatest reduction was seen in the smallest patients (total reduction 68% (16.72 ml/kg vs 5.36 ml/kg). Midazolam volumes in patients >20 kg was observed to increase (0.75 ml/kg vs. 0.95 ml/kg) but this did not have an impact on overall fluid burden.

CONCLUSIONS

Weight based sedation infusions may contribute to fluid overload related morbidity, especially in infants. An infant on morphine and midazolam at standard doses (20 mcg/kg/hr and 90 mcg/kg/hr respectively) will receive 16.7 ml/kg/day (33.4% of critical fluid overload at 48 hrs) when using weight-based infusions. Using standard concentrations reduces this volume to 5.36 ml/kg/day (10.7% of critical fluid overload at 48 hrs).