Variation in clinical usefulness of biomarkers of acute kidney injury in young children undergoing cardiac surgery

Tissue Inhibitor of Metalloproteinases-2 (TIMP-2) as a Prognostic Biomarker in Acute Kidney Injury: A Narrative Review

Acute kidney damage (AKI) is a serious and common consequence among critically unwell individuals. Traditional biomarkers, such as serum creatinine, frequently fail to detect AKI in its early stages, necessitating the development of new accurate early biomarkers. Tissue inhibitor of metalloproteinases 2 (TIMP-2) has emerged as a promising biomarker for predicting early AKI. The present narrative review investigates the role of TIMP-2 in AKI prediction in a variety of clinical scenarios. In the NephroCheck® test, TIMP-2 exceeds established biomarkers for the early identification of AKI in terms of sensitivity and specificity when combined with insulin-like growth factor-binding protein 7 (IGFBP-7). Elevated levels of these biomarkers can provide a warning signal for AKI two to three days before clinical symptoms appear. TIMP-2 and IGFBP-7 have high predictive values, with an area under the curve (AUC) typically above 0.8, indicating good predictive capacity. For example, the [TIMP-2] × [IGFBP-7] product produced an AUC of 0.85 in surgical patients at high risk. In critically ill patients, a threshold of 0.3 (ng/mL)2/1000 demonstrated 92% sensitivity and 72% specificity. Elevated TIMP-2 levels have been correlated with higher mortality rates and the need for renal replacement therapy (RRT). In sepsis-associated AKI (SA-AKI), TIMP-2 levels combined with clinical prognostic models improved predictive accuracy (AUC: 0.822). Furthermore, elevated urine TIMP-2 levels were good predictors of AKI in pediatric patients after cardiac surgery, with AUC-ROC values of up to 0.848. Urine output and the presence of concomitant disorders may influence the prognostic accuracy of these biomarkers; therefore, more research is needed to fully understand their utility. The predictive value of TIMP-2 could be strengthened by combining it with other clinical parameters, reinforcing its role in the early detection and treatment of AKI.

Simultaneous determination of multiple urine biomarkers for kidney injury using SPE combined with LC-MS/MS

BACKGROUND AND OBJECTIVES

Urinary biomarkers such as low molecular weight proteins and small molecular weight metabolites are crucial in the diagnosis of kidney injury. The objective of this study was to develop and preliminarily validate a sensitive and specific method using solid-phase extraction (SPE) in conjunction with liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous measurement of these biomarkers in human urine.

METHOD

This study presents the development of a solid-phase extraction method integrated with LC-MS/MS analyzing biomarkers including creatinine, urea, β2-microglobulin, α1-microglobulin, and cystatin C in human urine. An enhanced solid-phase cartridge technique was employed for peptide purification and dilution of small molecule metabolites during sample preparation.

RESULTS

The developed LC-MS/MS method achieved satisfactory separation of the five analytes within 15 min. Accuracy levels ranged from -8.6% to 13.6%. Both intra-assay and inter-assay imprecision rates were maintained below 7.9% for all analytes.

CONCLUSIONS

The established LC-MS/MS method effectively quantifies creatinine, urea, β2-microglobulin, α1-microglobulin and cystatin C concurrently. This offers a viable alternative for the detection of kidney injury biomarkers in human urine, demonstrating potential for clinical application in kidney injury diagnosis.

Association of Urine Biomarkers With Acute Kidney Injury and Fluid Overload in Infants After Cardiac Surgery: A Single Center Ancillary Cohort of the Steroids to Reduce Systemic Inflammation After Infant Heart Surgery Trial

To examine the association between three perioperative urine biomarker concentrations (urine cystatin C [uCysC], urine neutrophil gelatinase-associated lipocalin [uNGAL], and urine kidney injury molecule 1 [uKIM-1]), and cardiac surgery-associated acute kidney injury (CS-AKI) and fluid overload (FO) in infants with congenital heart disease undergoing surgery on cardiopulmonary bypass. To explore how urine biomarkers are associated with distinct CS-AKI phenotypes based on FO status.

DESIGN

Ancillary prospective cohort study.

SETTING

Single U.S. pediatric cardiac ICU.

PATIENTS

Infants less than 1 year old enrolled in the Steroids to Reduce Systemic Inflammation after Infant Heart Surgery trial (NCT03229538) who underwent heart surgery from June 2019 to May 2020 and opted into biomarker collection at a single center. Infants with preoperative CS-AKI were excluded.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Forty infants met inclusion criteria. Median (interquartile) age at surgery was 103 days (5.5-161 d). Modified Kidney Disease Improving Global Outcomes-defined CS-AKI was diagnosed in 22 (55%) infants and 21 (53%) developed FO. UCysC and uNGAL peaked in the early postoperative period and uKIM-1 peaked later. In unadjusted analysis, bypass time was longer, and Vasoactive-Inotropic Score at 24 hours was higher in infants with CS-AKI. On multivariable analysis, higher uCysC (odds ratio [OR], 1.023; 95% CI, 1.004-1.042) and uNGAL (OR, 1.019; 95% CI, 1.004-1.035) at 0-8 hours post-bypass were associated with FO. UCysC, uNGAL, and uKIM-1 did not significantly correlate with CS-AKI. In exploratory analyses of CS-AKI phenotypes, uCysC and uNGAL were highest in CS-AKI+/FO+ infants.

CONCLUSIONS

In this study, uCysC and uNGAL in the early postoperative period were associated with FO at 48 hours. UCysC, uNGAL, and uKIM-1 were not associated with CS-AKI. Further studies should focus on defining expected concentrations of these biomarkers, exploring CS-AKI phenotypes and outcomes, and establishing clinically meaningful endpoints for infants post-cardiac surgery.

The Use of Renal Biomarkers in Pediatric Cardiac Patients With Acute Kidney Injury

Acute kidney injury (AKI) is a common and serious condition that occurs in approximately 30% to 50% of pediatric patients that undergo cardiac surgery. Currently used parameters to measure kidney function (serum creatinine and urine output) are often unreliable and delay the prediction of AKI, despite their adoption into clinical guidelines. Emerging evidence suggests that biomarkers such as neutrophil gelatinase-associated lipocalin, cystatin C, interleukin-18, kidney injury molecule 1, and liver-type fatty acid– binding protein may be useful in the identification and location of pediatric renal injury. Ontogeny-related changes in tubular function and nephrogenesis result in reference values that differ based on age and sex. In addition, changes in endogenous concentrations may result from factors such as cardiopulmonary bypass. The use of urine samples to measure renal biomarkers offers a significant advantage compared with routine blood sampling, especially in the neonatal patient population. Future research is warranted to determine age-dependent changes in AKI biomarkers and the relationship with pharmacokinetic clearance of commonly used medications in the postoperative cardiac patient.

Novel Biomarkers of Heart Failure in Pediatrics

Novel biomarkers of heart failure are the subject of numerous studies. Biomarkers of heart failure can be determined in the blood and in the urine. Seven groups of biomarkers of heart failure based on pathophysiological mechanisms are presented in this review, namely biomarkers of myocardial stretch, myocyte injury, myocardial remodeling, biomarkers of inflammation, renal dysfunction, neurohumoral activation, and oxidative stress. Studies of biomarkers in the pediatric population are scarce, therefore, further investigation is needed for reliable prognostic and therapeutic implications. The future of biomarker use is in multimarker panels that include a combination of biomarkers with different pathophysiological mechanisms in order to improve their diagnostic and prognostic predictive value.

Assessing the value of serum and urinary interleukins for diagnosis of acute kidney injury in children and adolescents: A systematic review and meta-analysis

Introduction

Method

Results

Conclusion

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Urinary level of IL-18 is significantly higher in AKI children in comparison with non-AKI children.

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Serum levels of IL-6 and IL-8 are significantly higher in AKI children in comparison with non-AKI children.

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Overall, the sensitivity and specificity of these markers are not desirable for diagnosing AKI.

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Future studies should be directed towards unifying cut-off points for these markers.