N-GAL: diagnosing AKI as soon as possible

Urinary tract trauma as a predictor of acute kidney injury in severely injured patients: A retrospective analysis of observational studies

AIM

The main objective of this study was to determine whether urinary trauma increases the risk of acute kidney injury (AKI) in patients with severe trauma. As a secondary objective, we assessed the reliability of neutrophil gelatinase-associated lipocalin (NGAL) in the early prediction of AKI in this patient population.

METHODS

Retrospective analysis of two prospective observational studies involving 179 adult patients with severe trauma (Injury Severity Score >16). NGAL levels were measured by taking a blood sample 24 h after admission. AKI was diagnosed according to the Kidney Disease Improving Global Outcomes (KDIGO) classification.

RESULTS

The overall incidence of AKI was 29%. Kidney or vascular injury was an independent risk factor for AKI (risk ratio [RR] = 3.1, 95% confidence interval [CI] 1.93-4.90). Trauma to urinary passages was also associated with an increased risk of AKI (RR = 4.2, 95% CI 2.70-6.46). Among patients without urinary tract injury, serum NGAL levels were significantly higher in trauma patients who developed AKI during the first 5 days in the intensive care unit (ICU) compared to patients without this organ dysfunction (214.6 µg/L [IQR 167.3] vs. 90.6 µg/L [IQR 58.4]; P<0.001). In patients with urinary tract trauma, there was no difference in the NGAL levels between the two groups (184.6 µg/L [IQR 139.9] vs. 118.3 µg/L [IQR 118.1]; P=0.216). NGAL was not a reliable predictor of AKI in patients with urinary trauma (AUC 0.660).

CONCLUSION

Urinary tract injury is associated with a significant increase in AKI in patients with severe trauma during the first 5 days of hospitalization in the intensive care unit. In these patients, NGAL is not a reliable predictor of the development of AKI.

Lipocalin-2 as a biomarker for diabetic nephropathy

Diabetes is a major global public health issue. The prevalence of type 1 diabetes is comparatively static, as hereditary and genetic causes are involved, while type 2 diabetes (T2D) prevalence is increasing day by day. T2D is associated with chronic complications, including diabetic neuropathy (DN), nephropathy, retinopathy, and other complications like diabetic foot. DN is the main complication of both types of diabetes. DN can be diagnosed by routine laboratory tests, microalbuminuria > 300 mg/24 h, and a gradual decrease in glomerular filtration rate. As the appearance of microalbuminuria is a late manifestation, an early marker for renal damage is needed. Lipocalin-2, also known as neutrophil gelatinase-associated lipocalin (NGAL), is a small protein purified from neutrophil granules and a good marker for kidney disease. NGAL is a transporter protein responsible for many physiological processes, such as inflammation, generation of the immune response, and metabolic homeostasis. NGAL has been reported to depict the early changes in renal damage when urine microalbumin is still undetecable. Therefore, elucidating the role of NGAL in detecting DN and understanding its mechanism can help establish it as a potential early marker for DN.

suPAR: An Inflammatory Mediator for Kidneys

Background

Inflammation is a common feature of many kidney diseases. The implicated inflammatory mediators and their underlying molecular mechanisms however are often not clear.

Summary

suPAR is the soluble form of urokinase-type plasminogen activator receptor (uPAR), associated with inflammation and immune activation. It has evolved into a unique circulating kidney disease factor over the last 10 years. In particular, suPAR has multiple looks due to enzymatic cleavage and alternative transcriptional splicing of the uPAR gene. Most recently, suPAR has emerged as a systemic mediator for COVID-19 infection, associated with lung as well as kidney dysfunction. Like membrane-bound uPAR, suPAR could interact with integrins (e.g., αvβ3 integrin) on podocytes, providing the molecular basis for some glomerular kidney diseases. In addition, there have been numerous studies suggesting that suPAR connects acute kidney injury to chronic kidney disease as a special kidney risk factor. Moreover, the implication of circulating suPAR levels in kidney transplantation and plasmapheresis not only indicates its relevance in monitoring for recurrence but also implies suPAR as a possible therapeutic target. In fact, the therapeutic concept of manipulating suPAR function has been evidenced in several kidney disease experimental models.

Key Messages

The last 10 years of research has established suPAR as a unique inflammatory mediator for kidneys. While open questions remain and deserve additional studies, modulating suPAR function may represent a promising novel therapeutic strategy for kidney disease.

Utility of suPAR and NGAL for AKI Risk Stratification and Early Optimization of Renal Risk Medications among Older Patients in the Emergency Department

Diagnosis of acute kidney injury (AKI) based on plasma creatinine often lags behind actual changes in renal function. Here, we investigated early detection of AKI using the plasma soluble urokinase plasminogen activator receptor (suPAR) and neutrophil gelatinase-sssociated lipocalin (NGAL) and observed the impact of early detection on prescribing recommendations for renally-eliminated medications. This study is a secondary analysis of data from the DISABLMENT cohort on acutely admitted older (≥65 years) medical patients (n = 339). Presence of AKI according to kidney disease: improving global outcomes (KDIGO) criteria was identified from inclusion to 48 h after inclusion. Discriminatory power of suPAR and NGAL was determined by receiver-operating characteristic (ROC). Selected medications that are contraindicated in AKI were identified in Renbase®. A total of 33 (9.7%) patients developed AKI. Discriminatory power for suPAR and NGAL was 0.69 and 0.78, respectively, at a cutoff of 4.26 ng/mL and 139.5 ng/mL, respectively. The interaction of suPAR and NGAL yielded a discriminatory power of 0.80, which was significantly higher than for suPAR alone (p = 0.0059). Among patients with AKI, 22 (60.6%) used at least one medication that should be avoided in AKI. Overall, suPAR and NGAL levels were independently associated with incident AKI and their combination yielded excellent discriminatory power for risk determination of AKI.

Association of Platelets and White Blood Cells Subtypes with Trauma Patients' Mortality Outcome in the Intensive Care Unit

Background: White blood cell (WBC) subtypes have been suggested to reflect patients’ immune-inflammatory status. Furthermore, the derived ratio of platelets and WBC subtypes, including monocyte-to-lymphocyte ratio (MLR), neutrophil-to-lymphocyte ratio (NLR), and platelet-to-lymphocyte ratio (PLR), is proposed to be associated with patient outcome. Therefore, this study aimed to identify the association of platelets and white blood cells subtypes with the mortality outcome of trauma patients in the intensive care unit (ICU). Method: The medical information from 2854 adult trauma patients admitted to the ICU between 1 January 2009 and 31 December 2019 were retrospectively retrieved from the Trauma Registry System and classified into two groups: the survivors group (n = 2524) and the death group (n = 330). The levels of monocytes, neutrophils, lymphocytes, platelets, and blood-drawn laboratory data detected upon patient arrival to the emergency room and the derived MLR, NLR, and PLR were calculated. Multivariate logistic regression analysis was used to determine the independent effects of univariate predictive variables on mortality occurrence. Result: The results revealed the patients who died had significantly lower platelet counts (175,842 ± 61,713 vs. 206,890 ± 69,006/μL, p < 0.001) but higher levels of lymphocytes (2458 ± 1940 vs. 1971 ± 1453/μL, p < 0.001) than the surviving patients. However, monocyte and neutrophil levels were not significantly different between the death and survivor groups. Moreover, dead patients had a significantly lower PLR than survivors (124.3 ± 110.3 vs. 150.6 ± 106.5, p < 0.001). However, there was no significant difference in MLR or NLR between the dead patients and the survivors. Multivariate logistic regression revealed that male gender, old age, pre-existing hypertension, coronary artery disease and end-stage renal disease, lower Glasgow Coma Scale (GCS), higher Injury Severity Score (ISS), higher level of lymphocytes and lower level of red blood cells and platelets, longer activated partial thromboplastin time (aPTT), and lower level of PLR were independent risk factors associated with higher odds of trauma patient mortality outcome in the ICU. Conclusion: This study revealed that a higher lymphocyte count, lower platelet count, and a lower PLR were associated with higher risk of death in ICU trauma patients.

Ultramarathon and Renal Function: Does Exercise-Induced Acute Kidney Injury Really Exist in Common Conditions?

Background: Increasing ultramarathons participation, investigation into strenuous exercise and kidney function has to be clarified.

Study Design: Prospective observational study.

Methods and Protocol: The study used data collected among ultra-marathon runners completing the 2017 edition of the 120 km “Infernal trail” race. Samples were collected within 2 h pre-race (start) and immediately post-race (finish). Measurements of serum creatinine (sCr), cystatin C (Cys), creatine kinase, and urine albumin were completed. Acute Kidney Injury (AKI) as defined by the RIFLE criteria. “Risk” of injury was defined as increased serum Creatinine (sCr) × 1.5 or Glomerular Filtration Rate (GFR) decrease >25%. Injury was defined as 2 × sCr or GFR decrease >50%. These two categories of AKI were combined to calculate total incidence at the finish line. GFR was estimated by two methods, using measure of sCr and using measure of cystatin C. Urinary biomarkers [neutrophil gelatinase-associated lipocalin (NGAL)] were also used to define AKI. Outcome results before and after the race were compared by using McNemar test for qualitative data and Wilcoxon signed-rank test for quantitative data, in modified intent-to-treat and per-protocol analyses.

Results: A sample of 24 included finishers, with no use of non-steroidal anti-inflammatory drugs (NSAIDs) was studied. Depending the methodology used to calculate GFR, the prevalence of AKI was observed from 0 to 12.5%. Urinary biomarkers of kidney damage were increased following the race but with no significant decrease in GFR.

Discussion/Conclusion: Our study showed a very low prevalence of AKI and no evidence that ultra-endurance running can cause important kidney damage in properly hydrated subjects with no use of NSAIDs. Whether the increase in urinary biomarkers of kidney damage following the race reflects structural kidney injury or a simple metabolic adaptation to strenuous exercise needs to be clarified.

Predictive Value of Osteoprotegerin and Neutrophil Gelatinase-associated Lipocalin on Multiple Organ Failure in Multiple Trauma

BACKGROUND/AIM

Multiple organ dysfunction syndrome (MODS) is the leading cause of late posttraumatic mortality. This study analyzed the prognostic values of osteoprotegerin (OPG) and neutrophil gelatinase-associated lipocalin (NGAL/lipocalin 2) compared to interleukin-6 (IL-6) in multiply injured patients.

PATIENTS AND METHODS

A retrospective observational cohort study on multiply injured patients with an injury severity score (ISS) of ≥16 was performed. OPG, NGAL and IL-6 blood concentrations were measured. Statistical analysis comprised receiver-operating-characteristic (ROC) analysis with the corresponding area under the curve (AUC).

RESULTS

Thirty-nine patients with a mean ISS of 34±11 were included. Fourteen patients (36%) developed MODS and 8 patients (21%) died. Plasma levels of NGAL, OPG, and IL-6 were significantly elevated in the MODS+ group. Each biomarker positively correlated with MODS score and diagnosis of MODS.

CONCLUSION

NGAL and OPG might be indicative of MODS and could have the potential to be biomarkers in the early detection of patients at risk of posttraumatic MODS.

Quantification of NGAL in Urine of Endurance Cycling Athletes

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a glycoprotein released during early phases of a postischemic kidney in response to kidney injury, inflammation, and oxidative stress. It can be detected in urine after 2 hours of an ischemic event. The aim was to measure and to correlate the level of urine NGAL (uNGAL) with urea, creatinine, and glomerular filtration rate (GFR) of endurance cycling athletes (n = 19) and physically active individuals (control, n = 17).

METHODS

Quantification of urea and creatinine were performed by dry chemical method, and GFR was calculated using the modification of diet in renal disease formula, according to Brazilian Society of Nephrology. uNGAL analyses were performed by enzyme linked immunoabsorbent assay. Analyses were performed 48 hours after exercises.

RESULTS

uNGAL (in ng/mL) levels, expressed as median, minimum, and maximum, in cyclist group, 387.7 (109.7-1691.0), was significantly higher than that observed in control (physically active) group, 141.5 (4.8-657.0), (P < .05). No significant correlations were observed between uNGAL and creatinine, urea, or GFR (P > .05).

CONCLUSIONS

Results have pointed to increased uNGAL levels in endurance cycling athletes. Increase of uNGAL in absence of clinical signs or alterations in creatinine, urea, or GFR might suggest that there is metabolic adaptation to endurance exercise, or possibly predisposition to acute kidney injury over time.

The Role of Urinary Neutrophil Gelatinase-Associated Lipocalin in Predicting Acute Kidney Dysfunction in Patients With Liver Cirrhosis

Background

Early detection of acute kidney dysfunction (AKD) in cirrhotic patients is crucial. Urinary neutrophil gelatinase-associated lipocalin (uNGAL) has been identified as an early marker of AKD. The aim of the study was to evaluate serial uNGAL as a marker and predictor of AKD in liver cirrhosis patients.

Methods

Serial uNGAL and serum creatinine (sCr) levels were measured daily during the first 6 days of admission. Furthermore, sCr levels and the estimated glomerular filtration rate (eGFR) were measured after 3 - 6 weeks. The uNGAL levels in patients with and without abnormal sCr were compared.

Results

Fifty-seven consecutive cirrhotic patients were enrolled in the study. Eight of 14 patients (57%) who developed abnormal uNGAL level also had abnormal sCr level (odds ratio (OR) = 3.4, 95% CI: 0.99 - 12.03, P = 0.05). After 6 weeks, 41% of patients exhibited an abnormal uNGAL level and abnormal sCr (OR = 6.7, 95% CI: 1.55 - 28.85, P = 0.01). Area under the curve (AUROC) and the best cut-off point for highest NGAL in 6 days were 0.64 and 72.55 ng/mL, respectively.

Conclusions

There is a modest association between highest uNGAL in the first 6 days of admission and sCr at week 6 in all participants. This may indicate that in cirrhotic patients, uNGAL level during the first 6 days of admission has a potential predictability for the development of high sCr and low eGFR 6 weeks later. The AUROC of 0.64 quantifies the overall ability of uNGAL to discriminate between those individuals who will have a raised sCr levels and those who will not.

Use of biomarkers in pediatric sepsis: literature review

Despite advances in recent years, sepsis is still a leading cause of hospitalization and mortality in infants and children. The presence of biomarkers during the response to an infectious insult makes it possible to use such biomarkers in screening, diagnosis, prognosis (risk stratification), monitoring of therapeutic response, and rational use of antibiotics (for example, the determination of adequate treatment length). Studies of biomarkers in sepsis in children are still relatively scarce. This review addresses the use of biomarkers in sepsis in pediatric patients with emphasis on C-reactive protein, procalcitonin, interleukins 6, 8, and 18, human neutrophil gelatinase, and proadrenomedullin. Assessment of these biomarkers may be useful in the management of pediatric sepsis.

Evaluation of serum neutrophil gelatinase-associated lipocalin in predicting acute kidney injury in critically ill patients

Objective

This investigation evaluated the real-time point-of-care testing (RT-POCT) of neutrophil gelatinase-associated lipocalin (NGAL) for detecting acute kidney injury (AKI) and prognosis of critically ill patients.

Methods

A total of 249 critically ill patients in the emergency department (ED), who were diagnosed with acute decompensated heart failure, sepsis or diabetic ketoacidosis were enrolled in this study. All enrolled patients were followed up for 28 days or to death and the mortalities were recorded. Serum creatinine (sCr) and NGAL were measured.

Results

40.6% enrolled patients deteriorated to AKI during the observation period. The NGAL level was significantly higher in the AKI versus non-AKI group. The NGAL levels in the non-survivors group at 7-day and 28-day were significantly higher than in the survivors group. NGAL was detected as an independent risk factor of AKI, and 7-day and 28-day morality. The receiver operating characteristic curve of NGAL was calculated for diagnosing AKI; the area under the curve (AUC) was significantly higher than that of 1-day eGFR.

Conclusions

NGAL is an independent predictor of AKI, and 7-day and 28-day mortality in critically ill ED patients, and can be an early alert for AKI and useful for determining prognosis.

Short-term preconditioning enhances the therapeutic potential of adipose-derived stromal/stem cell-conditioned medium in cisplatin-induced acute kidney injury

The development of new strategies to preserve renal function after acute kidney injury (AKI) is necessary due to limited clinical intervention options. The organ-protective effects of mesenchymal stromal/stem cells (MSCs) and their conditioned medium (CM) have been investigated demonstrating that both separately promoted tubular recovery and ameliorated the outcome of AKI. Nevertheless, strategies to optimise the regenerative potential of both are highly needed. Here we investigated the effects of CM from adipose-derived MSCs (ASCs) preincubated in a hypoxic environment (Hyp). Protective factors were investigated by PCR analysis and a protein array in vitro. The expression of 64 of the 308 proteins assayed was found to be more than two-fold increased after Hyp. CM of Hyp-pretreated ASCs (pCM) was used to enhance regeneration in a mouse model of cisplatin-induced AKI (cisAKI). Renal function was assessed by measurements of markers for AKI and serum cytokine levels. The pCM significantly ameliorated serum creatinine and neutrophil gelatinase-associated lipocalin values, and also the levels of inflammatory cytokines IL-1β and IL-6 in the serum of mice with AKI. Our work clearly showed that a Hyp preconditioning significantly increases the release of protective factors in ASCs and enhances the therapeutic effects of CM in cisAKI in mice.

Effect of Kidney Function on Drug Kinetics and Dosing in Neonates, Infants, and Children

Neonates, infants, and children differ from adults in many aspects, not just in age, weight, and body composition. Growth, maturation and environmental factors affect drug kinetics, response and dosing in pediatric patients. Almost 80% of drugs have not been studied in children, and dosing of these drugs is derived from adult doses by adjusting for body weight/size. As developmental and maturational changes are complex processes, such simplified methods may result in subtherapeutic effects or adverse events. Kidney function is impaired during the first 2 years of life as a result of normal growth and development. Reduced kidney function during childhood has an impact not only on renal clearance but also on absorption, distribution, metabolism and nonrenal clearance of drugs. 'Omics'-based technologies, such as proteomics and metabolomics, can be leveraged to uncover novel markers for kidney function during normal development, acute kidney injury, and chronic diseases. Pharmacometric modeling and simulation can be applied to simplify the design of pediatric investigations, characterize the effects of kidney function on drug exposure and response, and fine-tune dosing in pediatric patients, especially in those with impaired kidney function. One case study of amikacin dosing in neonates with reduced kidney function is presented. Collaborative efforts between clinicians and scientists in academia, industry, and regulatory agencies are required to evaluate new renal biomarkers, collect and share prospective pharmacokinetic, genetic and clinical data, build integrated pharmacometric models for key drugs, optimize and standardize dosing strategies, develop bedside decision tools, and enhance labels of drugs utilized in neonates, infants, and children.

Urine neutrophil gelatinase-associated lipocalin: a diagnostic and prognostic marker for acute kidney injury (AKI) in hospitalized cirrhotic patients with AKI-prone conditions

BACKGROUND

Acute kidney injury (AKI) is known to increase mortality in hospitalized cirrhotic patients; therefore early identification is utmost significance. There are only a few studies evaluating the cut-off level of urine neutrophil gelatinase-associated lipocalin (uNGAL) for diagnosing AKI and its prognostic value in cirrhotic patients. We aimed to determine the accuracy of uNGAL as a biomarker for early identification of AKI and to determine the cut-off level of uNGAL for diagnosing AKI in hospitalized cirrhotic patients; and (2) to explore the association of 30-day liver-related mortality with uNGAL level.

METHODS AND MATERIAL

We prospectively enrolled cirrhotic patients admitted at the King Chulalongkorn Memorial Hospital during May 1, 2011 to Dec 31, 2013. UNGAL levels were measured within 24 h after admission. Clinical and laboratory data were obtained. Patients were followed up to 30 days.

RESULTS

Of 137 cirrhotic hospitalized patients, 121 cirrhotic patients (88.3 %) with AKI-prone conditions were included with mean age of 57.3 ± 14.7 years. Thirty-five patients (29 %) developed AKI within 72 h of admission. The causes of AKI were prerenal azotemia (68.6 %), acute tubular necrosis (25.7 %), hepatorenal syndrome (5.7 %), respectively. The mean uNGAL level was significantly higher in the patients who developed AKI compared with those who did not (290.6 ± 356.3 vs. 54.4 ± 73.7 ng/mL; P = 0.0001). The AUC of uNGAL for diagnosing AKI was 0.83 (95 % [CI]: 0.76-0.91) with the optimal cut-off level of 56 ng/mL, providing 77.1 % sensitivity and 73.3 % specificity. Fourteen percent of subjects died during the 30-day follow-up period. The mean uNGAL levels were significantly higher in the mortality group. The AUC of uNGAL in predicting mortality was 0.75 (95 % [CI]: 0.66-0.85), with a best cut-off level of 72 ng/mL providing 70.6 % sensitivity and 69.2 % specificity. However, in multivariate logistic regression analysis, uNGAL is not an independent factor for 30-day liver-related mortality prediction.

CONCLUSIONS

uNGAL is a valid marker for the early detection of AKI in hospitalized cirrhotic patients with AKI-prone conditions; however, its level could not independently predict 30-day liver-related mortality.

The role of urine neutrophil gelatinase--associated lipocalin (NGAL) in acute heart failure in patients with ST--elevation myocardial infarction

BACKGROUND

Neutrophil gelatinase-associated lipocalin (NGAL) is a novel early marker of acute kidney injury for which has been shown that it can also be released from the injured myocardium. Our aim was to correlate urine NGAL with markers of in-hospital heart failure in patients with acute ST-elevation myocardial infarction (STEMI).

METHODS

We prospectively included 61 consecutive STEMI patients after primary percutaneous coronary intervention and estimated admission and in-hospital urine NGAL, serum creatinine, troponin I, leucocytes, CRP, N-terminal pro brain natriuretic peptide (NT-proBNP) levels and ejection fraction by echocardiography. Urine NGAL levels were compared between patients with and without HF defined as serum NT-proBNP > 400 pmol/l and were correlated to markers of heart failure, inflammations and of kidney function.

RESULTS

Urine NGAL levels and CRP was significantly higher in participants with heart failure compared to those with NT-proBNP below 400 pmol/l. Urine NGAL level of 50 ng/ml had 90 % specificity for HF, the sensitivity was low at 25 %. Comparison of participants with NGAL levels < 50 ng/ml and ≥ 50 ng/ml at admission and after 12 h revealed a significant difference in NT-proBNP levels, left ventricle ejection fraction, markers of inflammation and of kidney function. Urine NGAL level was independently associated with NT-proBNP level.

CONCLUSIONS

The level of urine NGAL early after myocardial infarction is associated with NT-proBNP concentration and even NGAL levels below 137 ng/ml, the usually reported normal cut-off value, had high specificity for HF in our sample.

Complex alpine extrication: case report of mountain and speleological rescue cooperation

Mountain sporting activities are an increasingly popular practice that exposes mountaineers to a high risk of adverse events. This report describes a unique case of recovery in an austere environment that involved explosives. In June 2012, a 52-year-old man ascended a cliff tower in the Eastern Alps, Italy. A landslide occurred, and a boulder crushed the climber against a large stone located farther down the cliff, causing compression of the lower limbs and the pelvis with consequent severe musculoskeletal trauma. The National Alpine and Cave Rescue Unit (NACRU) arrived and proceeded with stabilization of the injured climber, which took 6 hours and involved a difficult extrication supported by the Cave Rescue division of NACRU. Unfortunately, during transport to the trauma center of Borgo Trento, Verona, the patient exhibited signs of progressive traumatic shock because of crush syndrome, hypovolemia, and acidosis, which led to cardiac arrest and death. Based on an extensive literature review, this report was determined to be the only one of a mountain rescue using explosives for the extrication of a victim in the Northeast Italian Alps. This case describes how a rescue in austere environments can represent a high-risk situation, and it shows how improvisation and cooperation between rescue teams are crucial for a successful recovery.

Clinical and prognostic implications of plasma NGAL and NT-proBNP in adult patients with congenital heart disease

BACKGROUND

Prognostic value of NT-proBNP is well established in patients with congenital heart disease. Growing evidence suggests that plasma NGAL is elevated in heart failure but data is limited in congenital heart disease. This study investigates the combined prognostic value of plasma NGAL with plasma NT-proBNP in adult patients with congenital heart disease.

METHODS

Plasma levels of NT-proBNP and NGAL were measured in 76 consecutive adult patients (33 men, mean age 31.7 ± 14 yrs) with congenital heart disease and normal values of serum creatinine. Patients were divided in three groups: A: simple cardiac lesions, B: complex cardiac lesions and C: cyanotic lesions. Patients were also monitored for long-term major cardiovascular events: death, hospitalization, NYHA class worsening, new onset of arrhythmias, surgical or percutaneous intervention.

RESULTS

NGAL value was significantly different between groups: In group A median NGAL value was 64.5 ± 36.7 ng/ml, in group B median NGAL value was 88.77 ± 36.17 ng/ml and in group C median NGAL value was 121 ± 40 ng/ml (group A vs. group B: p = 0.048, group B vs. group C: p = 0.037, group A vs. group C: p = 0.003). Plasma NT-proBNP predicted all events (HR = 1.001, CI = 1.001-1.002, p = 0.0006) as well as cardiovascular death alone (HR = 1.001, CI = 1.001-1.002, p = 0.0004); plasma NGAL was the only predictor of cardiovascular death (HR = 1.017, CI = 1.001-1.033, p = 0.037).

CONCLUSION

Plasma NGAL levels were lower in patients with simple congenital disease compared to patients with complex congenital heart disease and cyanotic congenital heart disease. Plasma NGAL levels correlated with NT-proBNP and could predict cardiovascular death in this small cohort of patients.

Rapid Detection of Acute Kidney Injury by Urinary Neutrophil Gelatinase-Associated Lipocalin in Patients Undergoing Cardiopulmonary Bypass

OBJECTIVE

Acute kidney injury (AKI) is common following cardiopulmonary bypass (CPB). The aim of this study is to determine the accuracy of urinary neutrophil gelatinase-associated lipocalin (NGAL) levels following cardiac surgery to establish the severity of renal impairment as compared to serum creatinine levels.

METHODS

A total number of 28 patients undergoing elective cardiopulmonary bypass were included. Diagnostic criteria of AKI was established in case of a percentage increase in serum creatinine concentration of >50%. Serum creatinine levels were recorded in the preoperative period before induction and in the postoperative period at 24, 48, and 72 hours. Urinary NGAL measurement was performed before induction and in the 4(th) postoperative hour. The duration of CPB surgery, hospital stay, and cross-clamp time were recorded.

RESULTS

Based on AKI criteria, subjects were grouped as AKI (n=11) and no AKI (n=19). Postoperative urinary NGAL levels were significantly higher in the group with AKI (11.8 ng mL(-1) vs. 104.0 ng mL(-1), p=0.003). In the AKI group, CPB time bypass (111.9 min vs. 82.7 min) and cross-clamp time (76.9 min vs. 59.1 min) were significantly higher. A cut-off of 25.5 ng mL(-1) yielded a sensitivity of 81.82% and a specificity of 94.12% at the postoperative 4(th) hour with an AUC of 0.947 for predication of AKI.

CONCLUSION

Urine NGAL rose significantly much earlier as compared to serum creatinine levels in the early postoperative period. Although larger case series are needed, we are of the opinion that urinary NGAL measurements may be used as an early clinical marker of AKI following CPB.

Urinary neutrophil gelatinase-associated lipocalin and the occurrence of delayed graft function after kidney transplant

OBJECTIVES

To investigate the predictive value of urinary neutrophil gelatinase-associated lipocalin in the occurrence of delayed graft function after kidney transplant.

MATERIALS AND METHODS

In this prospective cohort study of 67 consecutive patients who received a living-related (40 patients [61%]) or deceased-donor kidney transplant (27 patients [39%]), urinary neutrophil gelatinase-associated lipocalin was determined in the first 100 mL perfusate of the donor kidney and in urine at 6 hours after transplant. Patients were followed (11 ± 7 mo) for changes in estimated glomerular filtration rate and delayed graft function.

RESULTS

The mean urinary neutrophil gelatinase-associated lipocalin level at 6 hours after transplant was significantly higher after deceased-donor (781 ± 452 ng/mL) than living-donor transplant (229 ± 223 ng/mL; P ≤ 0.001). The decrease in estimated glomerular filtration rate from 6 to 12 months after transplant was positively correlated with the urinary neutrophil gelatinase-associated lipocalin levels in the perfusate in living-donor transplant. A significant correlation was noted between the occurrence of delayed graft function and the urinary neutrophil gelatinase-associated lipocalin level at 6 hours after living-donor transplant. In the deceased-donor group, the occurrence of delayed graft function was correlated with urinary neutrophil gelatinase-associated lipocalin levels in the perfusate. In deceased-donor kidney transplant, the mean urinary neutrophil gelatinase-associated lipocalin level in the perfusion fluid was significantly greater from donors who had terminal serum creatinine > 150 μmol/L, and urinary neutrophil gelatinase-associated lipocalin level at 6 hours after transplant was significantly greater in transplants with longer cold ischemia time and donors who had hypertension.

CONCLUSIONS

Urinary neutrophil gelatinase-associated lipocalin levels in the donor kidney perfusate and 6 hours after transplant may be a useful predictor of delayed graft function and decreased graft function from 6 to 12 months after transplant.

Novel biomarkers for the prediction of acute kidney injury in patients undergoing liver transplantation

AIM

Because of the delayed rise of serum creatinine concentrations, novel biomarkers such as NGAL, GST and KIM-1 are proposed to detect acute kidney injury (AKI). In this study we evaluated these biomarkers.

MATERIALS & METHODS

Twenty-six consecutive adult liver transplantations were evaluated. Markers were measured at four different time points during an intensive care unit admission.

RESULTS

Plasma NGAL detected AKI with an optimal area under the curve at 8 h after admission (0.86; p = 0.004) and at 4 h after admission for urinary NGAL (0.80; p = 0.012). The other markers failed to detect AKI.

CONCLUSION

NGAL is a promising biomarker for detecting AKI in patients after liver transplantation.

Prognostic value of plasma neutrophil gelatinase-associated lipocalin for mortality in patients with heart failure

BACKGROUND

In patients with heart failure, renal dysfunction is associated with a poor outcome. We aimed to assess the prognostic value of plasma neutrophil gelatinase-associated lipocalin (NGAL), a novel marker of renal tubular damage, in patients with heart failure with or without renal dysfunction, and compare it with 2 frequently used biomarkers of chronic kidney disease.

METHODS AND RESULTS

Plasma NGAL, estimated glomerular filtration rate (eGFR), and cystatin C were assessed in 562 patients with heart failure. Chronic kidney disease was defined as eGFR<60 mL/min per 1.73 m2. Outcome was all-cause mortality at 36 months. Mean age was 71±11 years, 61% were men, and 97% were in New York Heart Association functional class II/III. Mean baseline eGFR was 54±20 mL/min per 1.73 m2, mean cystatin C was 11.2 (7.7-16.2) mg/L, and median plasma NGAL was 85 (60-123) ng/mL. Higher plasma NGAL levels were independently associated with an increased risk of all-cause mortality, in patients with and without chronic kidney disease (hazard ratio [per SD increase in log NGAL]=1.45 [1.22-1.72]; P<0.001 and hazard ratio=1.51 [1.06-2.16]; P=0.023, respectively). Similarly, both in patients with high and low cystatin C (median cut-off), higher plasma NGAL levels were independently associated with an increased risk of all-cause mortality. Moreover, when NGAL was entered in the multivariable risk prediction model, eGFR (P=0.616) and cystatin C (P=0.937) were no longer associated with mortality.

CONCLUSIONS

Plasma NGAL predicts mortality in patients with heart failure, both in patients with and without chronic kidney disease and is a stronger predictor for mortality than the established renal function indices eGFR and cystatin C.

[Analysis of neutrophil gelatinase-associated lipocalin in the critical patient]

OBJECTIVE

To determine if NGAL value exceeding 150 ng/mL is a good diagnostic test for acute renal failure in critically ill patients.

DESIGN

Prospective, observational cohort.

SETTING

Intensive Care Unit and Cardiac Surgery Intensive Care Service at Hospital Germans Trias I Pujol.

PARTICIPANTS

Patients admitted to the Intensive Care department the Designated days in the studio.

INTERVENTIONS

Analysis of serum creatinine blood given from 7 days prior to the start of the study, and daily during 4 weeks and by determination of NGAL urine test in frozen sample, analyzer ARCHITECT (Abbott Diagnostics) determined by immunoassay the day baseline and 2 times a week for 4 weeks, analysis of the stay and mortality.

RESULTS

A total of 529 NGAL samples were obtained from 46 patients. 37% of patients had a value of NGAL>150 ng/mL. The Sensivity of the test to diagnose acute renal failure was 69%, Specifity was 75,7%. However, the Positive Predictive Test Value was 53%, which means that 47% of patients with high NGAL did not develop AKI. A NGAL >150 mg/dL was associated with a significantly higher SOFA and a longer stay in the ICU. The mortality of patients with elevated NGAL was 58.8%.

CONCLUSIONS

A NGAL>150 ng/mL does not seem to be an excellent test for AKI in critically ill patients but is associated with a worse prognosis.

Urinary neutrophil gelatinase-associated lipocalin (NGAL) is associated with mortality in a community-based cohort of older Swedish men

OBJECTIVE

Neutrophil gelatinase-associated lipocalin (NGAL) indicates tubular kidney damage, neutrophil activation and possibly atherogenesis, however the prospective association between urinary NGAL (u-NGAL) and cardiovascular death in the community is not known.

METHODS

This study evaluates the association between urinary and serum NGAL and mortality in a Swedish population of 597 men aged 78 years. During the study (median follow-up 8.1 years) 261 men died, 90 of cardiovascular causes.

RESULTS

U-NGAL was associated with increased all-cause and cardiovascular mortality (HR 2.0 for quartile 4 vs. quartile 1, 95% CI 1.0-4.0, P < 0.05) in Cox regression models independently of cardiovascular risk factors, CRP and cystatin C estimated glomerular filtration rate (eGFRCysC) but not urinary Albumin (u-Alb). A combination of low eGFRCysC (≤60 mL/min), high u-Alb (≥3 mg/mmol Cr) and high u-NGAL (≥1.19 μg/mmol Cr) was associated with a 9-fold increased cardiovascular mortality (P < 0.001) and a 3-fold increased all-cause mortality (P < 0.001). Serum NGAL was associated with increased all-cause mortality risk independent of other cardiovascular risk factors (HR 1.4 for quartile 4 vs.1, 95% CI 1.0-1.9, P < 0.05) but not after adjustment with CRP, eGFRCysC or u-Alb.

CONCLUSION

This community study is the first to show that the tubular kidney biomarker u-NGAL associated with increased cardiovascular and all-cause mortality independent of cardiovascular risk factors and glomerular filtration. Additional research is needed to evaluate the utility of NGAL in clinical practice.

Association between plasma neutrophil gelatinase associated lipocalin level and obstructive sleep apnea or nocturnal intermittent hypoxia

BACKGROUND

Both obstructive sleep apnea (OSA) and a novel lipocalin, neutrophil gelatinase associated lipocalin (Ngal), have been reported to be closely linked with cardiovascular disease and loss of kidney function through chronic inflammation. However, the relationship between OSA and Ngal has never been investigated.

OBJECTIVES

To evaluate the relationship between Ngal and OSA in clinical practice.

METHODS

In 102 patients, polysomnography was performed to diagnose OSA and plasma Ngal levels were measured. The correlations between Ngal levels and OSA severity and other clinical variables were evaluated. Of the 46 patients who began treatment with continuous positive airway pressure (CPAP), Ngal levels were reevaluated after three months of treatment in 25 patients.

RESULTS

The Ngal level correlated significantly with OSA severity as determined by the apnea hypopnea index (r = 0.24, p = 0.01) and 4% oxygen desaturation index (ODI) (r = 0.26, p = 0.01). Multiple regression analysis showed that the Ngal level was associated with 4%ODI independently of other clinical variables. Compliance was good in 13 of the 25 patients who used CPAP. Although the OSA (4%ODI: 33.1±16.7 to 1.1±1.9/h, p<0.01) had significantly improved in those with good compliance, the Ngal levels were not significantly changed (60.5±18.1 before CPAP vs 64.2±13.9 ng/ml after CPAP, p = 0.27).

CONCLUSIONS

Plasma Ngal levels were positively associated with the severity of OSA. However, the contribution rate of OSA to systemic Ngal secretion was small and changes in Ngal levels appeared to be influenced largely by other confounding factors. Therefore, it does not seem reasonable to use the Ngal level as a specific biomarker of OSA in clinical practice.

Day-to-day variation of urinary NGAL and rational for creatinine correction

OBJECTIVES

The number of clinical studies evaluating the new tubular biomarker urinary neutrophil gelatinase-associated lipocalin (U-NGAL) in urine are increasing. There is no consensus whether absolute U-NGAL concentrations or urinary NGAL/creatinine (U-NGAL/Cr) ratios should be used when chronic tubular dysfunction is studied. The aim was to study the biological variation of U-NGAL in healthy subjects and the rational for urinary creatinine (U-Cr) correction in two different study samples.

DESIGN AND METHODS

To study biological variation of U-NGAL and U-NGAL/Cr ratio and the association between U-NGAL and U-Cr in healthy subjects 13 young males and females (median age 29 years) collected morning urine in 10 consecutive days. Additionally, a random subsample of 400 males from a population-based cohort (aged 78 years) collecting 24-hour urine during 1 day was studied.

RESULTS

The calculated biological variation for absolute U-NGAL was 27% and for U-NGAL/Cr ratio, 101%. Absolute U-NGAL increased linearly with U-Cr concentration (the theoretical basis for creatinine adjustment) in the older males (R=0.19, P<0.001) and with borderline significance in the young adults (R=0.16, P=0.08). The U-NGAL/Cr ratio was, however, negatively associated with creatinine in the older males (R=-0.14, P<0.01) and in the young adults (R=-0.16, P=0.07) indicating a slight "overadjustment."

CONCLUSIONS

The study provides some support for the use of U-NGAL/Cr ratio but the rather large biological variation and risk of possible overadjustment need to be considered. Both absolute U-NGAL and U-NGAL/Cr ratios should be reported for the estimation of chronic tubular dysfunction.

The appropriate use of biomarkers in heart failure

Natriuretic peptides and troponins have been extensively studied and used in heart failure, and their value has been extensively discussed. Renal markers, such as cystasin-C, NGAL, and KIM-1, have shown growing utility in heart failure. The activation of compensatory pathways and ongoing hemodynamic changes result in the release of biomarkers that can be monitored to chart disease progression and possibly target for therapy.

Enabling innovative translational research in acute kidney injury

Acute kidney injury (AKI) is a common, heterogeneous, and detrimental clinical condition that has significant attributable morbidity and mortality. Despite major advances in understanding the epidemiology, pathogenesis, and outcomes of AKI, preventive measures remain inadequate and therapeutic approaches (except for renal replacement therapy) have largely proven futile so far. Critical to the process of designing rational therapies is translational research, which involves the transition between the basic research discoveries and everyday clinical applications to prevent, diagnose, and treat human diseases. Progress in innovative approaches has been hampered due in part to the reliance on functional markers (serum creatinine and blood urea nitrogen) that are neither sensitive nor specific to diagnose AKI. This limitation has created a great deal of interest and intense investigation to identify a "troponin-like marker" that would facilitate recognition of AKI and allow for timely implementation of the precise therapeutic agent. The other major obstacle in this field is the diverse and complex nature of AKI that involves multiple independent and overlapping pathways, making it difficult to cure AKI with a single approach. In this review, we will summarize the advances, ongoing studies, and future perspectives in the field of translational research of AKI.

Intraoperative hyperglycemia augments ischemia reperfusion injury in renal transplantation: a prospective study

Background. Diabetes is a risk factor for delayed graft function in kidney transplantation, and hyperglycemia increases ischemia reperfusion injury in animal models. Methods. To explore the role of perioperative hyperglycemia in ischemia reperfusion injury, we conducted a prospective study of 40 patients undergoing living donor renal transplantation. Blood glucose levels were monitored intraoperatively, and serum samples were obtained at the time anesthesia was induced and one hour after allograft reperfusion. The percentage change in neutrophil gelatinase-associated lipocalin (NGAL), a protein whose expression is increased with renal ischemia, was then used to determine the extent of injury. Results. In a multivariate model including recipient, donor, and transplant factors, recipient blood glucose >160 mg/dL at the time of allograft reperfusion (β 0.19, P-value < 0.01), warm ischemia time >30 minutes (β 0.11, P-value 0.13), and recipient age (β 0.05, P-value 0.05) were associated with percentage change in NGAL. These same predictors were associated with the percentage change in creatinine on postoperative day 2. Conclusions. Hyperglycemia is associated with increased ischemic injury in renal transplantation. Both creatinine and NGAL, a marker of ischemic injury and renal function, fall less rapidly in patients with elevated blood glucose.

Albuminuria, proteinuria, and novel urine biomarkers as predictors of long-term allograft outcomes in kidney transplant recipients

BACKGROUND

Proteinuria is an established marker of decreased kidney function after kidney transplant. It recently has been suggested that albuminuria might be a more reliable marker. Although albuminuria often is regarded as a marker of glomerular damage, because chronic renal allograft damage is believed to be predominantly an interstitial process, albuminuria in this case might reflect tubular damage. Accordingly, we investigated the value of albuminuria, proteinuria, and tubular damage markers (KIM-1 [kidney injury molecule 1], NAG [N-acetyl-β-d-glucosaminidase], NGAL [neutrophil gelatinase-associated lipocalin], and H-FABP [heart fatty acid binding protein]) in predicting graft outcome in kidney transplant recipients.

STUDY DESIGN

Prospective observational cohort study.

SETTING & PARTICIPANTS

606 patients visiting our outpatient kidney transplant clinic in 2001-2003 were included and used in the analysis for death-censored graft failure. Median follow-up was 4.7 (25th-75th percentile, 3.8-5.2) years. 577 patients had follow-up longer than 1 year and were included in the analysis for estimated glomerular filtration rate (eGFR) decrease. Median follow-up was 3.2 (25th-75th percentile, 2.7-3.7) years.

PREDICTORS

Urine protein, albumin, and tubular damage markers in 24-hour urine samples.

OUTCOMES

Death-censored graft failure and decrease in eGFR.

RESULTS

There were 42 patients with graft failure; mean eGFR change was -0.46 ± 3.7 (standard deviation) mL/min/1.73 m(2)/y. The area under the receiver operating characteristic curve for death-censored graft failure showed that albuminuria (0.78; 95% CI, 0.59-0.76) was significantly higher than proteinuria (0.67; 95% CI, 0.59-0.76; P = 0.001), NGAL (0.63; 95% CI, 0.52-0.74; P = 0.02), and H-FABP (0.62; 95% CI, 0.53-0.73; P = 0.005) and not significantly different from KIM-1 (0.74; 95% CI, 0.66-0.82) and NAG (0.75; 95% CI, 0.67-0.83). Results were similar for the eGFR decrease outcome.

LIMITATIONS

Single-center observational study.

CONCLUSIONS

Measuring albuminuria may provide superior predictions for long-term renal outcomes after kidney transplant than total proteinuria. Additional assessment of urinary excretion of tubular damage markers may have limited value.

Neutrophil gelatinase-associated lipocalin at ICU admission predicts for acute kidney injury in adult patients

RATIONALE

Measured at intensive care unit admission (ICU), the predictive value of neutrophil gelatinase-associated lipocalin (NGAL) for severe acute kidney injury (AKI) is unclear.

OBJECTIVES

To assess the ability of plasma and urine NGAL to predict severe AKI in adult critically ill patients.

METHODS

Prospective-cohort study consisting of 632 consecutive patients.

MEASUREMENTS AND MAIN RESULTS

Samples were analyzed by Triage immunoassay for NGAL expression. The primary outcome measure was occurrence of AKI based on Risk-Injury-Failure (RIFLE) classification during the first week of ICU stay. A total of 171 (27%) patients developed AKI. Of these 67, 48, and 56 were classified as RIFLE R, I, and F, respectively. Plasma and urine NGAL values at ICU admission were significantly related to AKI severity. The areas under the receiver operating characteristic curves for plasma and urine NGAL were for RIFLE R (0.77 ± 0.05 and 0.80 ± 0.04, respectively), RIFLE I (0.80 ± 0.06 and 0.85 ± 0.04, respectively), and RIFLE F (0.86 ± 0.06 and 0.88 ± 0.04, respectively) and comparable with those of admission estimated glomerular filtration rate (eGFR) (0.84 ± 0.04, 0.87 ± 0.04, and 0.92 ± 0.04, respectively). Plasma and urine NGAL significantly contributed to the accuracy of the "most efficient clinical model" with the best four variables including eGFR, improving the area under the curve for RIFLE F prediction to 0.96 ± 0.02 and 0.95 ± 0.01. Serial NGAL measurements did not provide additional information for the prediction of RIFLE F.

CONCLUSIONS

NGAL measured at ICU admission predicts the development of severe AKI similarly to serum creatinine-derived eGFR. However, NGAL adds significant accuracy to this prediction in combination with eGFR alone or with other clinical parameters and has an interesting predictive value in patients with normal serum creatinine.

From kidney to cardiovascular diseases: NGAL as a biomarker beyond the confines of nephrology

Neutrophil gelatinase-associated lipocalin (NGAL), a small 25 kDa stress-protein released from injured tubular cells after various damaging stimuli, is already known by nephrologists as one of the most promising biomarkers of incoming Acute Kidney Injury. Moreover, recent studies seem to suggest a potential involvement of this factor also in the genesis and progression of chronic kidney diseases. This brief review explores the new interesting involvement of NGAL in the experimental and clinical field of cardiovascular diseases, such as the pathogenesis and clinical manifestations of atherosclerosis, acute myocardial infarction and heart failure. It does not seem difficult that, in the next future, NGAL may become a new missing link between the kidney and the cardiovascular system.

Year in review 2008: Critical Care--nephrology

We summarize original research in the field of critical care nephrology accepted or published during 2008 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Three main topics have been identified for a rapid overview. (1) The classification of acute kidney injury, with particular attention to differences and similarities between the RIFLE and AKIN classifications. (2) Fluid balance in patients requiring renal replacement therapy (RRT) has been shown as an independent risk factor for mortality in critically ill patients: current evidence and uncertainties are described. (3) Management of anticoagulation during RRT has been explored by several researchers in 2008: diagnosis of heparin-induced thrombocytopenia, the use of tirofiban and optimal anticoagulation during drotrecogin A activated treatment have been evaluated.

Plasma neutrophil gelatinase-associated lipocalin is an early marker of acute kidney injury in adult critically ill patients: a prospective study

PURPOSE

The aim of the study was to assess the ability of plasma neutrophil gelatinase-associated lipocalin (pNGAL) to predict acute kidney injury (AKI) in adult intensive care unit (ICU) patients.

METHODS

All consecutives patients admitted to 3 ICUs were enrolled in this prospective-observational study. Plasma neutrophil gelatinase-associated lipocalin was analyzed at ICU admission. Risk, injury, failure, loss, and end-stage kidney (RIFLE) criteria were calculated at admission and for each day during the first week. Patients were classified according to whether they met the threshold for RIFLE criteria (RIFLE 0 or 1) at admission and during the first week. Four groups were identified: RIFLE (0-0), (1-1), (1-0), and (0-1).

RESULTS

During this 1-month period, 88 patients were included in the study. Thirty-six patients met the criteria for RIFLE 0-0 with a mean pNGAL of 98 +/- 60 nmol/L, 22 for RIFLE 1-1 with a mean pNGAL of 516 +/- 221 nmol/L, and 20 patients had no AKI at admission but develop AKI at 48 hours (24-96 hours) (RIFLE 0-1) with a pNGAL of 342 +/- 183 nmol/L. Ten patients met the criteria for RIFLE 1-0 and had a mean pNGAL of 169 +/- 100 nmol/L. Using a cutoff of 155 nmol/L, sensitivity and specificity to predict AKI were 82% and 97%, respectively (area under the curve [AUC] = 0.92 [0.852-0.972]; P = .001). Looking at the patients without AKI at admission (n = 56) and who developed (n = 20) or did not develop (n = 36) AKI, receiver operating characteristic curve analysis was as follows: AUC = 0.956 (0.864-0.992). Sensitivity was 85% and specificity was 97%. Of the 7 patients who required renal replacement therapy, all of them had pNGAL of more than 303 nmol/L (AUC = 0.788 [0.687-0.868]).

CONCLUSION

Plasma neutrophil gelatinase-associated lipocalin at ICU admission is an early biomarker of AKI in adult ICU patients. Plasma neutrophil gelatinase-associated lipocalin increased 48 hours before RIFLE criteria.

NGAL: a biomarker of acute kidney injury and other systemic conditions

Neutrophil gelatinase-associated lipocalin (NGAL) is a 25 kDa protein belonging to the lipocalin superfamily. It was initially found in activated neutrophils, however, many other cells, like kidney tubular cells, may produce NGAL in response to various insults. Recently, it has been found to have a role in iron metabolism by virtue of its binding with siderophores. It has also been found to have a role in kidney development and tubular regeneration after injury. In experimental studies, it was found to be highly expressed in response to tubular injury. In subsequent clinical studies, urine NGAL has been found to be an early predictor for acute kidney injury (AKI). Newer devices for early bedside detection of NGAL are now available. Since serum creatinine is known to be an inadequate and late marker of AKI, NGAL might soon emerge as a troponin-like early marker for AKI. Recent evidence also suggests its role as a biomarker in a variety of other renal and non-renal conditions.

Assays of urine levels of HNL/NGAL in patients undergoing cardiac surgery and the impact of antibody configuration on their clinical performances

BACKGROUND

Acute kidney injury (AKI) is one of the most serious postoperative complications of cardiac surgery. The lack of early and powerful markers for AKI makes the morbidity and mortality still very high. HNL (Human neutrophil lipocalin)/NGAL (Neutrophil gelatinase-associated lipocalin) was recently shown as a novel biomarker for AKI after cardiac surgery.

METHODS

Serial urine samples from 59 patients undergoing cardiac surgery were analyzed by polyclonal antibody based radioimmunoassay (RIA), monoclonal-polyclonal antibody based enzyme-linked immunosorbent assay (ELISA).

RESULTS

We found 10 to 100-fold increases in urine HNL/NGAL levels in about half of the patients 2 h after termination of the operation and elevated levels in all patients 72 h post operation. The urine levels of HNL/NGAL showed a weak, but significant relation with kidney function as measured by plasma levels of cystatin C or creatinine. The 2 h-HNL/NGAL levels were positively correlated to extracorporeal circulation time (p<0001). The assays were well correlated, but had different clinical performances.

CONCLUSIONS

We confirmed that urine HNL/NGAL may be a useful early biomarker of postoperative kidney injury. The results indicate that the antibody configuration of the assay has an impact on the clinical performance of the assay.

Year in review 2007: Critical Care--nephrology

We summarize original research in the field of critical care nephrology that was accepted for publication or published in 2007 in Critical Care and, when considered relevant or directly linked to this research, in other journals. Four main topics were identified for a brief overview. The first of these was the definition of acute kidney injury and recent evidence showing the validity of RIFLE (Risk, Injury, Failure, Loss and End-stage kidney disease) criteria and the recent Acute Kidney Injury Network review of the same criteria. Second, we cover the clinical and experimental utilization of novel biomarkers for diagnosis of acute kidney injury, giving special attention to neutrophil gelatinase-associated lipocalin protein. The third area selected for review is outcomes of acute kidney injury during the past 10 years, described by a recent Austrailian epidemiological study. Finally, specific technical features of renal replacement therapies were examined in 2007, specifically regarding anticoagulation and vascular access.

Emerging urinary biomarkers in the diagnosis of acute kidney injury

BACKGROUND: Acute kidney injury (AKI) represents a common and devastating problem in clinical medicine. The lack of early biomarkers for AKI has led to a delay in initiating potentially effective therapies. OBJECTIVE: Identification of novel urinary biomarkers for AKI that have progressed to the clinical phase of the biomarker discovery process. METHODS: A literature review (PubMed, MedLine) from 2000 to the present. RESULTS/CONCLUSIONS;: The most promising AKI biomarkers include neutrophil gelatinase-associated lipocalin, IL-18, kidney injury molecule-1 and liver-type fatty acid binding protein. Studies to validate the sensitivity and specificity of these biomarkers in clinical samples from large cohorts and from multiple clinical situations are in progress, facilitated by the development of commercial tools for their measurement.