Clinical Use of the Urine Biomarker [TIMP-2] × [IGFBP7] for Acute Kidney Injury Risk Assessment

The Accuracy of Urinary TIMP-2 and IGFBP7 for the Diagnosis of Cardiac Surgery-Associated Acute Kidney Injury: A Systematic Review and Meta-Analysis

Background:

Tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) are recent promising markers for identification of cardiac surgery-associated acute kidney injury (CSA-AKI). The aim of this study was systematically and quantitatively to evaluate the accuracy of urinary TIMP-2 and IGFBP7 for the diagnosis of CSA-AKI.

Methods:

Three databases including PubMed, ISI web of knowledge, and Embase were systematically searched from inception to March 2018. Two investigators conducted the processes of literature search study selection, data extraction, and quality evaluation independently. Meta-DiSc and STATA were used for all statistical analyses.

Results:

A total of 8 studies comprising 552 patients were included in this meta-analysis. Pooled sensitivity and specificity with corresponding 95% confidence intervals (CIs) were 0.79 (95% CI, 0.71-0.86, I 2 = 74.2%) and 0.76 (95% CI, 0.72-0.80, I 2 = 80.8%), respectively. Pooled positive likelihood ratio (LR), negative LR, and diagnostic odds ratio were 3.49 (95% CI, 2.44-5.00, I 2 = 61.5%), 0.31(95% CI, 0.19-0.51, I 2 = 51.8%), and 14.89 (95% CI, 7.31-30.32, I 2 = 27.9%), respectively. The area under curve estimated by summary receiver operating characteristic was 0.868 (standard error [SE] 0.032) with a Q* value of 0.799 (SE 0.032). Sensitivity analysis demonstrated that one study notably affected the stability of pooled results. One of the subgroups investigated—AKI threshold—could account for partial heterogeneity.

Conclusion:

Urinary TIMP-2 and IGFBP7 is a helpful biomarker for early diagnosis of CSA-AKI. And, the potential of this biomarker with a broader spectrum of clinical settings may be the focus of future studies.

Toward Precision Medicine in the Cardiorenal Syndrome

Although the field of oncology has made significant steps toward individualized precision medicine, cardiology and nephrology still often use a "one size fits all" approach. This applies to the intersection of the heart-kidney interaction and the cardiorenal syndrome as well. Recent studies have shown that the prognostic implications of worsening renal function (WRF) in acute heart failure are variable; thus, there is a need to differentiate the implications of WRF to better guide precise care. This may best be performed with biomarkers that can give the clinician a real-time evaluation of the physiologic state at the time of developing WRF. This review will summarize current cardiac and renal biomarkers and their status in the evaluation of cardiorenal syndrome. Although we have made progress in our understanding of this syndrome, further investigation is needed to bring precision medicine into routine clinical practice for the care of patients with cardiorenal syndrome.

Impact of Isolyte Versus 0.9% Saline on Postoperative Event of Acute Kidney Injury Assayed by Urinary [TIMP-2] × [IGFBP7] in Patients Undergoing Cardiac Surgery

OBJECTIVE

Administration of excess chloride in 0.9% normal saline (NS) decreases renal perfusion and glomerular filtration rate, thereby increasing the risk for acute kidney injury (AKI). In this study, the effect of NS versus Isolyte use during cardiac surgery on urinary levels of tissue inhibitor of metalloproteinase 2 and insulin-like growth factor-binding protein 7 [TIMP-2] × [IGFBP7] and postoperative risk of AKI were examined.

DESIGN

Prospective, randomized, and single-blinded trial.

SETTING

Single university medical center.

PARTICIPANTS

Thirty patients over 18 years without chronic renal insufficiency or recent AKI undergoing elective cardiac surgery.

INTERVENTIONS

Subjects were randomized to receive either NS or Isolyte during the intraoperative period.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the change in urinary levels of [TIMP2] × [IGFBP7] from before surgery to 24 hours postoperatively. Secondary outcomes included serum creatinine pre- and postoperatively at 24 and 48 hours, serum chloride pre- and postoperatively at 24 and 48 hours, need for dialysis prior to discharge, and arterial pH measured 24 hours postoperatively. Sixteen patients received NS and 14 patients received Isolyte. Three patients developed AKI within the first 3 postoperative days, all in the NS group. The authors found increases in [TIMP-2] × [IGFBP7] in both groups. However, the difference in this increase between study arms was not significant (p = 0.92; -0.097 to 0.107).

CONCLUSION

The authors observed no change in urinary [TIMP-] × [IGFBP7] levels in patients receiving NS versus Isolyte during cardiac surgery. Future larger studies in patients at higher risk for AKI are recommended to evaluate the impact of high- versus lower-chloride solutions on the risk of postoperative AKI after cardiac surgery.

Plasma and urinary p21: potential biomarkers of AKI and renal aging

p21 is upregulated in renal tubules in response to acute kidney injury ( AKI). and localizes in the nucleus, where it induces cell cycle arrest (CCA). These events can mitigate early injury but can also facilitate the onset of the degenerative cell senescence/"aging" process. Hence, we asked the following: 1) can AKI-induced p21 upregulation be gauged by plasma and/or urinary p21 assay; 2) might p21 serve as an AKI/CCA biomarker; and 3) does p21 accumulate during normal renal aging, and might plasma p21 reflect this process? Mice were subjected to either ischemia-reperfusion (I/R) or nephotoxic (maleate) AKI. Renal cortical p21 expression (protein, mRNA) was assessed 2-18 h later and contrasted with plasma/urine p21 concentrations (ELISA). p21 mRNA/protein levels were also measured in aging mice (2, 12, 24 mo). AKI induced marked, progressive, increases in renal cortical p21 mRNA and protein levels. These changes were marked by acute (within 2-4 h) and profound increases (up to 200×) in both plasma and urine p21 concentrations. Renal I/R also activated p21 gene expression in extrarenal organs (heart, brain), consistent with so-called "organ cross talk". p21 efflux from damaged cells was confirmed with studies of hypoxia-injured, isolated proximal tubules. Aging was associated with progressive renal cortical p21 expression, which correlated ( r, 0.83) with rising plasma p21 concentrations. We concluded that 1) during AKI, renal p21 increases can be gauged by either plasma or urine p21 assay, serving as potentially useful AKI/CCA biomarkers; 2) AKI can activate p21 in extrarenal organs; and 3) plasma p21 levels may provide an index of the renal/systemic aging process.

Innovative Use of Novel Biomarkers to Improve the Safety of Renally Eliminated and Nephrotoxic Medications

Over the last decade, the discovery of novel renal biomarkers and research on their use to improve medication effectiveness and safety has expanded considerably. Pharmacists are uniquely positioned to leverage this new technology for renal assessment to improve medication dosing and monitoring. Serum cystatin C is a relatively new, inexpensive, functional renal biomarker that responds more quickly to changing renal function than creatinine and is not meaningfully affected by age, sex, skeletal muscle mass, dietary intake, or deconditioning. Cystatin C has been proposed as an adjunct or alternative to creatinine for glomerular filtration rate assessment and estimation of drug clearance. Tissue inhibitor of metalloproteinase-2·insulin-like growth factor-binding protein 7 ([TIMP-2]·[IGFBP7]) is a composite of two damage biomarkers released into the urine at a checkpoint in mitosis when renal cells undergo stress or sense a future risk of damage. Concentrations of [TIMP-2]·[IGFBP7] increase before a rise in serum creatinine is evident, thus providing insightful information for evaluation in the context of other patient data to predict the risk for impending kidney injury. This article provides a brief overview of novel renal biomarkers being used as a mechanism to improve medication safety including a discussion of cystatin C, as part of drug-dosing algorithms and specifically for vancomycin dosing, and the use of [TIMP-2]·[IGFBP7] for risk prediction in acute kidney injury and drug-induced kidney disease. Select cases of clinical experience with novel renal biomarkers are outlined, and lessons learned and future applications are described.

Mechanisms Underlying Increased TIMP2 and IGFBP7 Urinary Excretion in Experimental AKI

BACKGROUND

Recent clinical data support the utility/superiority of a new AKI biomarker ("NephroCheck"), the arithmetic product of urinary TIMP × IGFBP7 concentrations. However, the pathophysiologic basis for its utility remains ill defined.

METHODS

To clarify this issue, CD-1 mice were subjected to either nephrotoxic (glycerol, maleate) or ischemic AKI. Urinary TIMP2/IGFBP7 concentrations were determined at 4 and 18 hours postinjury and compared with urinary albumin levels. Gene transcription was assessed by measuring renal cortical and/or medullary TIMP2/IGFBP7 mRNAs (4 and 18 hours after AKI induction). For comparison, the mRNAs of three renal "stress" biomarkers (NGAL, heme oxygenase 1, and p21) were assessed. Renal cortical TIMP2/IGFBP7 protein was gauged by ELISA. Proximal tubule-specific TIMP2/IGFBP7 was assessed by immunohistochemistry.

RESULTS

Each AKI model induced prompt (4 hours) and marked urinary TIMP2/IGFBP7 increases without an increase in renal cortical concentrations. Furthermore, TIMP2/IGFBP7 mRNAs remained at normal levels. Endotoxemia also failed to increase TIMP2/IGFBP7 mRNAs. In contrast, each AKI model provoked massive NGAL, HO-1, and p21 mRNA increases, confirming that a renal "stress response" had occurred. Urinary albumin rose up to 100-fold and strongly correlated (r=0.87-0.91) with urinary TIMP2/IGFBP7 concentrations. Immunohistochemistry showed progressive TIMP2/IGFBP7 losses from injured proximal tubule cells. Competitive inhibition of endocytic protein reabsorption in normal mice tripled urinary TIMP2/IGFBP7 levels, confirming this pathway's role in determining urinary excretion.

CONCLUSIONS

AKI-induced urinary TIMP2/IGFBP7 elevations are not due to stress-induced gene transcription. Rather, increased filtration, decreased tubule reabsorption, and proximal tubule cell TIMP2/IGFBP7 urinary leakage seem to be the most likely mechanisms.

Evaluation of KIM-1 as an early biomarker of snakebite-induced AKI in mice

Acute kidney injury (AKI) is one of the most important complications of bothropic poisoning and its early identification remains challenging. The nephrotoxicity of Bothrops insularis venom (BinsV) was previously described by our research group. In this study, we continued to evaluate the effect of BinsV on kidney function in mice and LLC-MK2 proximal tubule cells, evaluating KIM-1 protein as an early AKI biomarker. Male Swiss mice were inoculated with BinsV intramuscularly and observed for 24 h in a metabolic cage model. Urine and blood were collected for biochemical analyses and the kidneys were examined for oxide-reducing balance and submitted to histological analysis. LLC-MK2 cells incubated with BinsV were assessed for cell viability and cell death mechanism by flow cytometry. Histological analysis of the kidneys indicated AKI and the oxide-reducing analyses demonstrated a decreasing in reduced glutathione (GSH) levels and an increasing on Malondialdehyde (MDA) levels. BinsV was cytotoxic to LLC-MK2 and the cytometry analyses suggested necrosis. Within 24 h after the envenomation, urinary creatinine did not increase, but the urinary levels of KIM-1 increased. In conclusion, we found AKI evidence in the kidney tissue and the increase in the KIM-1 levels suggest it can be used as an early AKI biomarker.

Clinical Relevance and Predictive Value of Damage Biomarkers of Drug-Induced Kidney Injury

Nephrotoxin exposure accounts for up to one-fourth of acute kidney injury episodes in hospitalized patients, and the associated consequences are as severe as acute kidney injury due to other etiologies. As the use of nephrotoxic agents represents one of the few modifiable risk factors for acute kidney injury, clinicians must be able to identify patients at high risk for drug-induced kidney injury rapidly. Recently, significant advancements have been made in the field of biomarker utilization for the prediction and detection of acute kidney injury. Such biomarkers may have a role both for detection of drug-induced kidney disease and implementation of preventative and therapeutic strategies designed to mitigate injury. In this article, basic principles of renal biomarker use in practice are summarized, and the existing evidence for six markers specifically used to detect drug-induced kidney injury are outlined, including liver-type fatty acid binding protein, neutrophil gelatinase-associated lipocalin, tissue inhibitor of metalloproteinase-2 times insulin-like growth factor-binding protein 7 ([TIMP-2]·[IGFBP7]), kidney injury molecule-1 and N-acetyl-β-D-glucosaminidase. The results of the literature search for these six kidney damage biomarkers identified 29 unique articles with none detected for liver-type fatty acid binding protein and [TIMP-2]·[IGFBP7]. For three biomarkers, kidney injury molecule-1, neutrophil gelatinase-associated lipocalin and N-acetyl-β-D-glucosaminidase, the majority of the studies suggest utility in clinical practice. While many questions need to be answered to clearly articulate the use of biomarkers to predict drug-induced kidney disease, current data are promising.

Predictive value of cell cycle arrest biomarkers for cardiac surgery-associated acute kidney injury: a meta-analysis

BACKGROUND

A biomarker test based on a combination of urine tissue inhibitor of metalloproteinases 2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) has been used as a potential biomarker of acute kidney injury (AKI). This meta-analysis aimed to evaluate the predictive value of this biomarker for cardiac surgery-associated acute kidney injury (CSA-AKI).

METHODS

We searched MEDLINE, PubMed, Cochrane, and EMBASE for studies. We evaluated the methodological quality of each included study using the Quality Assessment of Diagnostic Accuracy Studies 2 criteria. Meta-DiSc and STATA were used for statistical analyses.

RESULTS

A total of 10 studies (747 patients) were included in this meta-analysis. Pooled sensitivity and specificity with corresponding 95% confidence intervals (CI) were 0.77 (95% CI: 0.70-0.83, I²=40.7%) and 0.76 (95% CI: 0.72-0.79, I²=69.1%), respectively. Pooled positive likelihood ratio (LR), negative LR, and diagnostic odds ratio were 3.26 (95% CI: 2.51-4.23, I²=50.7%), 0.32 (95% CI: 0.24-0.41, I²=6.7%), and 10.08 (95% CI: 6.85-14.84, I²=6.7%), respectively. The area under the curve estimated by summary receiver operating characteristics was 0.83 [standard error (SE) 0.023] with a Q* value of 0.759 (se 0.021). There was no heterogeneity amongst the 10 studies from both threshold and non-threshold effects. Subgroup analysis showed that the diagnostic value was related to the severity of AKI and time measurement.

CONCLUSIONS

Urinary [TIMP-2]·[IGFBP7] is an effective predictive test for cardiac surgery associated acute kidney injury with good diagnostic accuracy within 24 h. Studies examining use of biomarker-guided care bundles are indicated.

Renal protection in the 21st century

PURPOSE OF REVIEW

Among critically ill patients, acute kidney injury (AKI) is still a common and serious complication with a tremendous impact on short-term and long-term outcomes. The objective of this review is to discuss strategies for renal protection and prevention of AKI in ICU patients.

RECENT FINDINGS

It is fundamental to identify patients at risk for AKI as soon as possible and as accurately as possible. In order to achieve these goals, translational approaches implementing new biomarkers have shown promising results. Focusing on the role of potential preventive strategies, hemodynamic stabilization is the most important intervention with proven efficacy. Recent published data undermined any hope that high-dose statin therapy in statin-naïve patients could exert renoprotective effects. However, preliminary data revealed the renoprotective activity of dexmedetomidine when used as a sedative agent. Moreover, several studies demonstrated the protective effects of remote ischemic preconditioning in various organs including the kidneys. The use of balanced crystalloid instead of hyperchloremic solutions also contributes to the reduction of AKI in critically ill patients.

SUMMARY

To prevent AKI, it is crucial to identify patients at risk as early as possible. Establishing hemodynamic stability and an adequate intravascular volume state to ensure a sufficient perfusion pressure is the only effective therapeutic intervention. It is self-evident that nephrotoxic agents should be avoided whenever it is possible.

Biomarkers of Sepsis-Induced Acute Kidney Injury

Sepsis, an infection-induced systemic disease, leads to pathological, physiological, and biochemical abnormalities in the body. Organ dysfunction is caused by a dysregulated host response to infection during sepsis which is a major contributing factor to acute kidney injury (AKI) and the mortality rate for sepsis doubles due to coincidence of AKI. Sepsis-induced AKI is strongly associated with increased mortality and other adverse outcomes. More timely diagnosis would allow for earlier intervention and could improve patient outcomes. Sepsis-induced AKI is characterized by a distinct pathophysiology compared with other diseases and may also have unique patterns of plasma and urinary biomarkers. This concise review summarizes properties and perspectives of the biomarkers for their individual clinical utilization.

The use of cell cycle arrest biomarkers in the early detection of acute kidney injury. Is this the new renal troponin?

Acute kidney injury (AKI) has a high prevalence in critical care patients. Early detection might prevent patients from developing chronic kidney disease and requirement for renal replacement therapy. If we compare AKI with acute coronary syndrome, in which an increase in cardiac troponin may trigger early diagnosis and therapeutic intervention, we could extrapolate a similar technique in patients with early AKI without changes in urinary frequency or serum creatinine. The objective is to identify biomarker-positive, creatinine-negative patients that would allow therapeutic interventions to be initiated before finding changes in serum creatinine, preventing kidney damage. Tissue inhibitor of metalloproteinase 2 and insulin-like growth factor binding protein 7 are cell cycle arrest biomarkers that have demonstrated, in recent clinical trials, to have good sensitivity and specificity for early detection of AKI. Other recent studies have shown that the joint use of these biomarkers with serum creatinine and urine production could improve the prognosis of AKI in critical patients. The application of these biomarkers in clinical practice would enable the early identification of patients at risk of AKI, establishing interventions that would improve the survival of renal function.

Is acute kidney injury a harbinger for chronic kidney disease?

PURPOSE OF REVIEW

Despite abundant evidence in adults, the relationship between acute kidney injury (AKI) and chronic kidney disease (CKD) remains unanswered in pediatrics. Obstacles to overcome include the challenges defining these entities and the lack of long-term follow-up studies. This review focuses on pediatric populations at high-risk for AKI, the evidence of the long-term effect of AKI on renal health, and biomarkers to detect renal disease.

RECENT FINDINGS

AKI in critically ill children and neonates is common and independently associated with adverse outcomes. Patients with diabetes and sickle cell disease along with neonates with necrotizing enterocolitis have been identified as high-risk for AKI. Preterm birth and neonates with AKI have signs of renal dysfunction early in childhood. Urinary biomarkers may identify AKI and CKD earlier than traditional biomarkers, but more work is necessary to determine their clinical utility. Promising technological advances including the ability to determine nephron number noninvasively will expand our ability to characterize the AKI to CKD transition.

SUMMARY

AKI is common and associated with poor outcomes. It is probable that AKI is a harbinger to CKD in pediatric populations. However, we currently lack the tools to definitely answer this question and more research is needed.

Response to different furosemide doses predicts AKI progression in ICU patients with elevated plasma NGAL levels

BACKGROUND

Furosemide responsiveness (FR) is determined by urine output after furosemide administration and has recently been evaluated as a furosemide stress test (FST) for predicting severe acute kidney injury (AKI) progression. Although a standardized furosemide dose is required for FST, variable dosing is typically employed based on illness severity, including renal dysfunction in the clinical setting. This study aimed to evaluate whether FR with different furosemide doses can predict AKI progression. We further evaluated the combination of an AKI biomarker, plasma neutrophil gelatinase-associated lipocalin (NGAL), and FR for predicting AKI progression.

RESULTS

We retrospectively analyzed 95 patients who were treated with bolus furosemide in our medical-surgical intensive care unit. Patients who had already developed AKI stage 3 were excluded. A total of 18 patients developed AKI stage 3 within 1 week. Receiver operating curve analysis revealed that the area under the curve (AUC) values of FR and plasma NGAL were 0.87 (0.73-0.94) and 0.80 (0.67-0.88) for AKI progression, respectively. When plasma NGAL level was < 142 ng/mL, only one patient developed stage 3 AKI, indicating that plasma NGAL measurements were sufficient to predict AKI progression. We further evaluated the performance of FR in 51 patients with plasma NGAL levels > 142 ng/mL. FR was associated with AUC of 0.84 (0.67-0.94) for AKI progression in this population with high NGAL levels.

CONCLUSIONS

Although different variable doses of furosemide were administered, FR revealed favorable efficacy for predicting AKI progression even in patients with high plasma NGAL levels. This suggests that a combination of FR and biomarkers can stratify the risk of AKI progression in a clinical setting.

Urinary biomarkers of cell cycle arrest are delayed predictors of acute kidney injury after pediatric cardiopulmonary bypass

BACKGROUND

Several novel biomarkers that predict acute kidney injury (AKI) have recently been proposed. We have evaluated the sequential patterns of biomarker elevation after pediatric cardiopulmonary bypass (CPB) and determined their diagnostic accuracy.

METHODS

We measured the ability of neutrophil gelatinase-associated lipocalin (NGAL), interleukin-18 (IL-18), liver type fatty-acid binding protein (L-FABP), kidney injury molecule-1 (KIM-1), tissue inhibitor of metalloproteinase-2 (TIMP-2), and insulin-like growth factor binding protein 7 (IGFBP7), to predict AKI (≥50% increase in serum creatinine from baseline). Areas under the receiver-operator characteristic curves (AUCs) were calculated for each biomarker and for various biomarker combinations at multiple time points after CPB.

RESULTS

Of 150 patients examined, AKI had developed in 50 patients by 24 h after CPB, with an elevated NGAL concentration first noted at 2 h post-CPB, increases in IL-18, L-FABP, and the product of TIMP-2 and IGFBP7 first noted at 6 h, and an elevated KIM-1 level noted at 12 h. At each time point, urine NGAL remained the marker with the highest predictive ability (AUC > 0.9). The addition of any other biomarker did not increase the predictive accuracy of NGAL alone at 2 and 6 h. At 12 h, when compared to NGAL alone, the combination of NGAL, IL-18, and TIMP2 improved the AUC for AKI prediction (from 0.938 to 0.973).

CONCLUSIONS

While urine NGAL remains a superior stand-alone test at the 2 and 6 h time points after pediatric CPB, a panel of carefully selected biomarkers may prove optimal at later time points.

The cellular selection between apoptosis and autophagy: roles of vitamin D, glucose and immune response in diabetic nephropathy

BACKGROUND AND AIMS

Apoptosis, autophagy and cell cycle arrest are cellular responses to injury which are supposed to play fundamental roles in initiation and progression of diabetic nephropathy (DN). The aims of the present study is to shed light on the potential effects of vitamin D analog 22-oxacalcitriol (OCT) on different cell responses during DN, and the possible interplay between both glucose, immune system and vitamin D in determining the cell fate.

METHOD

All rats were randomly allocated into one of three groups: control, vehicle-treated DN group and OCT-treated DN group. Eight weeks after induction of diabetes, the rats were killed. Fasting blood glucose levels, serum 25 (OH) D, renal functions, cytokines and gene expression of autophagy, apoptotic and cell cycle arrest markers were assessed. In addition, the histological assessment of renal architecture was done.

RESULTS

OCT treatment remarkably improved the renal functions and albuminuria. The reductions in mesangial cell hypertrophy, extracellular matrix as well as cell loss were significantly associated with upregulation of pro-autophagy gene expressions and downregulation of both pro-apoptotic and G1-cell cycle arrest genes expression. The reno-protective effects of OCT treatment were associated with significant attenuation of the fasting blood glucose, serum IL-6, renal TLR-4 and IFN-g gene expression.

CONCLUSION

Modulator effects of OCT on glucose and immune system play important roles in renal cell fate decision and chronic kidney disease progression.

Biomarkers for Early Detection of Acute Kidney Injury

BACKGROUND

Acute kidney injury (AKI) is common in hospitalized patients and is associated with increased morbidity, mortality, and cost. Currently, AKI is diagnosed after symptoms manifest; available diagnostic tests (e.g., serum creatinine, urine microscopy, urine output) have limited ability to identify subclinical AKI. Because of the lack of treatment strategies, AKI typically is managed with supportive measures. However, strategies exist that may prevent renal insults in critically ill patients; therefore, early recognition of AKI is crucial for minimizing damage propagation.

CONTENT

Experimental and clinical studies have identified biomarkers that may facilitate earlier recognition of AKI or even identify patients at risk of AKI. Such biomarkers might aid in earlier implementation of preventive strategies to slow disease progression and potentially improve outcomes. This review describes some of the most promising novel biomarkers of AKI, including neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule 1 (KIM-1), interleukin 18 (lL-18), liver-type fatty-acid-binding protein (L-FABP), insulin-like-growth-factor-binding protein 7 (IGFBP7), and tissue inhibitor of metalloproteinase 2 (TIMP-2).

SUMMARY

We discuss biomarker test characteristics, their strengths and weaknesses, and future directions of their clinical implementation.

Practical approach to detection and management of acute kidney injury in critically ill patient

Background

Acute kidney injury (AKI) is a common complication in critically ill patients and is associated with high morbidity and mortality. This paper provides a critical review of the etiologies of AKI and a systematic approach toward its diagnosis and management with emphasis on fluid volume assessment and the use of urine biochemical profile and microscopy in identifying the nature and the site of kidney injury.

Materials and methods

The search of PubMed and selection of papers had employed observational designs or randomized control trials relevant to AKI.

Results

AKI is defined by the rate of rise of serum creatinine and a decline in urine output. The pathophysiology is diverse and requires a careful and systematic assessment of predisposing factors and localization of site of injury. The majority of AKIs are due to prerenal causes such as fluid volume deficit, sepsis, or renal as in acute tubular injury. The use of central venous and arterial blood pressure monitoring and inferior vena cava echocardiography complemented by urine analysis and microscopy allows assessment of fluid volume status and AKI etiology.

Conclusions

Timely intervention by avoidance of fluid volume deficit and nephrotoxic agents and blood pressure support can reduce the incidence of AKI in critically ill patients.

TIMP-2*IGFBP7 (Nephrocheck®) Measurements at Intensive Care Unit Admission After Cardiac Surgery are Predictive for Acute Kidney Injury Within 48 Hours

BACKGROUND/AIMS

Acute kidney injury (AKI) is a postoperative complication after cardiac surgery with a high impact on mortality and morbidity. Nephrocheck® [TIMP-2*IGFBP7] determines markers of tubular stress, which occurs prior to tubular damage. It is unknown at which time-point [TIMP-2*IGFBP7] measurement should be performed to ideally predict AKI. We investigated the association of [TIMP-2*IGFBP7] at various time-points with the incidence of AKI in patients undergoing elective cardiac surgery including cardio-pulmonary bypass.

METHODS

In a prospective cohort study, serial blood and urine samples were collected from 150 patients: pre-operative, at ICU-admission, 24h and 48h post-surgery. AKI was defined as Serum-Creatinine rise >0.3 mg/dl within 48hrs. Urinary [TIMP-2*IGFBP7] was measured at pre-operative, ICU-admission and 24h post-surgery; medical staff was kept blinded to these results.

RESULTS

A total of 35 patients (23.5%) experienced AKI, with a higher incidence in those with high [TIMP-2*IGFBP7] values at ICU admission (57.1% vs. 10.1%, p<0.001). In logistic regression [TIMP-2*IGFBP7] at ICU admission was independently associated with the occurrence of AKI (Odds Ratio 11.83; p<0.001, C-statistic= 0.74) after adjustment for EuroSCORE II and CBP-time.

CONCLUSIONS

Early detection of elevated [TIMP-2*IGFBP7] at ICU admission was strongly predictive for postoperative AKI and appeared to be more precise as compared to subsequent measurements.

Urinary Matrix Metalloproteinase-7 Predicts Severe AKI and Poor Outcomes after Cardiac Surgery

Urinary matrix metalloproteinase-7 (uMMP-7) levels consistently reflect the activity of intrarenal Wnt/β-catenin, which is activated in AKI models. To test the hypothesis that uMMP-7 is a predictor for severe AKI in patients after cardiac surgery, we performed a prospective, multicenter, two-stage cohort study in 721 patients undergoing cardiac surgery. In stage 1, we enrolled 323 children from three academic medical centers. In stage 2, we enrolled 398 adults at six centers. We analyzed levels of uMMP-7 and other injury biomarkers during the perioperative period. Severe AKI was defined as Kidney Disease Improving Global Outcomes stage 2 or 3. uMMP-7 level peaked within 6 hours after surgery in patients who subsequently developed severe AKI. After multivariate adjustment, the highest quintile of postoperative uMMP-7 level, compared with the lowest quintile, associated with 17-fold (in adults) and 36-fold (in children) higher odds of severe AKI. Elevated uMMP-7 level associated with increased risk of composite events (severe AKI, acute dialysis, and in-hospital death) and longer stay in the intensive care unit and hospital. For predicting severe AKI, uMMP-7 had an area under the receiver operating characteristic curve of 0.81 (in children) and 0.76 (in adults), outperforming urinary IL-18, angiotensinogen, neutrophil gelatinase-associated lipocalin, albumin-to-creatinine ratio, and tissue inhibitor of metalloproteinase-2·IGF-binding protein-7 and the clinical model. uMMP-7 significantly improved risk reclassification over the clinical model alone, as measured by net reclassification improvement and integrated discrimination improvement. In conclusion, uMMP-7 is a promising predictor for severe AKI and poor in-hospital outcomes in patients after cardiac surgery.

The diagnostic accuracy of urinary [TIMP-2]·[IGFBP7] for acute kidney injury in adults: A PRISMA-compliant meta-analysis

INTRODUCTION

Early diagnosis of acute kidney injury (AKI) remains a challenge. Recently, [TIMP-2]·[IGFBP7], which is a combination of urine tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor (IGF) binding protein 7 (IGFBP7), has been identified as a potential biomarker of AKI. We performed this meta-analysis to assess the diagnostic accuracy of urinary [TIMP-2]·[IGFBP7] for AKI in adult patients.

METHODS

We searched the PubMed, Embase, and Cochrane Library databases from database inception to March 2017. Two authors independently screened articles based on inclusion and exclusion criteria and assessed the methodological quality of each included study using the Quality Assessment of Diagnostic Accuracy Studies 2 criteria. Review Manager and STATA were used for all statistical analyses.

RESULTS

Nine studies (n = 1886) satisfied the inclusion criteria. Pooled analyses demonstrated that urinary [TIMP-2]·[IGFBP7] exhibited fair diagnostic accuracy for AKI (sensitivity [SEN] 0.83 [95% CI 0.75-0.89], specificity [SPE] 0.72 [95% CI 0.56-0.84], and area under the summary receiver operating characteristic [SROC] curve 0.86 [95% CI 0.82-0.88]) and AKI stage ≥ 2 (according to the 2012 Kidney Disease: Improving Global Outcomes [KDIGO] 2012 classification system; SEN 0.92 [95% CI 0.81-0.96], SPE 0.63 [95% CI 0.49-0.74], and area under the SROC curve 0.88 [95% CI 0.85-0.91]) in adult patients.

CONCLUSION

Our findings indicate that urinary [TIMP-2]·[IGFBP7] may be a reliable biomarker for the early detection of AKI. However, given the significant heterogeneity among the included studies, clinicians should be aware of the utility and limitations of this biomarker in clinical practice. Additional high-quality studies examining a larger sample of patients are required.

Urinary TIMP-2 and IGFBP7 for the prediction of acute kidney injury following cardiac surgery

Background

Acute kidney injury (AKI) following cardiac surgery is common and associated with poor patient outcomes. Early risk assessment for development of AKI remains a challenge. The combination of urinary tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor binding protein 7 (IGFBP7) has been shown to be an excellent predictor of AKI following cardiac surgery, but reported studies are for predominately non-Asian populations.

Methods

Adult patients were prospectively enrolled at Zhongshan hospital in Shanghai, China. The primary analysis was prediction of AKI and stage 2–3 AKI by [TIMP-2]*[IGFBP7] measured 4 h after postoperative ICU admission assessed using receiver operating characteristic curve (ROC) analysis. Kinetics of [TIMP-2]*[IGFBP7] following ICU admission were also examined.

Results

We prospectively enrolled 57 cardiac surgery patients, of which 20 (35%) developed AKI and 6 (11%) developed stage 2–3 AKI. The area under the ROC curve (AUC) of [TIMP-2]*[IGFBP7] at 4 h after ICU admission was 0.80 (95% confidence interval (CI): 0.68–0.91) for development of AKI and 0.83 (95% CI: 0.69–0.96) for development of stage 2–3 AKI. Urinary [TIMP-2]*[IGFBP7] values at 4 h after ICU admission were significantly (P < 0.001) higher in patients who developed AKI than in patients who did not develop AKI (mean (standard error) of 1.08 (0.34) (ng/mL)²/1000 and 0.29 (0.05) (ng/mL)²/1000, respectively). The time-profile of [TIMP-2]*[IGFBP7] suggests the markers started to elevate by the time of ICU admission in patients who developed AKI and either decreased or remained flat in patients without AKI.

Conclusion

The combination of urinary TIMP-2 and IGFBP7 4 h after postoperative ICU admission identifies patients at risk for developing AKI, not just stage 2–3 AKI following cardiac surgery.

Epidural analgesia in critically ill patients with acute pancreatitis: the multicentre randomised controlled EPIPAN study protocol

BACKGROUND

Acute pancreatitis (AP) is associated with high morbidity and mortality in its most severe forms. Most patients with severe AP require intubation and invasive mechanical ventilation, frequently for more than 7 days, which is associated with the worst outcome. Recent increasing evidence from preclinical and clinical studies support the beneficial effects of epidural analgesia (EA) in AP, such as increased gut barrier function and splanchnic, pancreatic and renal perfusion, decreased liver damage and inflammatory response, and reduced mortality. Because recent studies suggest that EA might be a safe procedure in the critically ill, we sought to determine whether EA reduced AP-associated respiratory failure and other major clinical outcomes in patients with AP.

METHODS AND ANALYSIS

The Epidural Analgesia for Pancreatitis (EPIPAN) trial is an investigator-initiated, prospective, multicentre, randomised controlled two-arm trial with assessor-blinded outcome assessment. The EPIPAN trial will randomise 148 patients with AP requiring admission to an intensive care unit (ICU) to receive EA (with patient-controlled epidural administration of ropivacaine and sufentanil) combined with standard care based on current recommendations on the treatment of AP (interventional group), or standard care alone (reference group). The primary outcome is the number of ventilator-free days at day 30. Secondary outcomes include main complications of AP (eg, organ failure and mortality, among others), levels of biological markers of systemic inflammation, epithelial lung injury, renal failure, and healthcare-associated costs.

ETHICS AND DISSEMINATION

The study was approved by the appropriate ethics committee (CPP Sud-Est VI). Informed consent is required. If the combined application of EA and standard care proves superior to standard care alone in patients with AP in the ICU, the use of EA may become standard practice in experienced centres, thereby decreasing potential complications related to AP and its burden in critically ill patients. The results will be disseminated in a peer-reviewed journal.

TRIAL REGISTRATION NUMBER

NCT02126332.

Management of patients at risk of acute kidney injury

Acute kidney injury (AKI) is a multifaceted syndrome that occurs in different settings. The course of AKI can be variable, from single hit and complete recovery, to multiple hits resulting in end-stage renal disease. No interventions to improve outcomes of established AKI have yet been developed, so prevention and early diagnosis are key. Awareness campaigns and education for health-care professionals on diagnosis and management of AKI-with attention to avoidance of volume depletion, hypotension, and nephrotoxic interventions-coupled with electronic early warning systems where available can improve outcomes. Biomarker-based strategies have not shown improvements in outcome. Fluid management should aim for early, rapid restoration of circulatory volume, but should be more limited after the first 24-48 h to avoid volume overload. Use of balanced crystalloid solutions versus normal saline remains controversial. Renal replacement therapy should only be started on the basis of hard criteria, but should not be delayed when criteria are met. On the basis of recent evidence, the risk of contrast-induced AKI might be overestimated for many conditions.

Urinary neprilysin in the critically ill patient

Background

Critically ill patients in intensive care face hazardous conditions. Among these, acute kidney injury (AKI) is frequently seen as a result of sepsis. Early diagnosis of kidney injury is of the utmost importance in the guidance of interventions or avoidance of treatment-induced kidney injury. On these grounds, we searched for markers that could indicate proximal tubular cell injury.

Methods

Urine samples of 90 patients admitted to the intensive or intermediate care unit were collected over 2 to 5 days. The biomarker neprilysin (NEP) was investigated in urine using several methods such as dot blot, ELISA and immunofluorescence of urinary casts. Fifty-five healthy donors acted as controls.

Results

NEP was highly significantly elevated in the urine of patients who suffered AKI according to the KDIGO criteria in comparison to healthy controls. It was also found to be elevated in ICU patients without overt signs of AKI according to serum creatinine changes, however they were suffering from potential nephrotoxic insults. According to our findings, urinary NEP is indicative of epithelial cell alterations at the proximal tubule. This was elaborated in ICU patients when ghost fragments and NEP⁺ microvesicles were observed in urinary sediment cytopreparations. Furthermore, NEP⁺ immunofluorescence of healthy kidney tissue showed staining at the proximal tubules.

Conclusions

NEP, a potential marker for proximal tubular epithelia, can be measured in urine. This does not originate from leakage of elevated serum levels, but indicates proximal tubular cell alterations such as brush border severing, which can heal in most cases.

Acute Kidney Injury Recognition in Low- and Middle-Income Countries

Acute kidney injury (AKI) is increasingly common around the world. Because of the low availability of effective therapies and resource limitations, early preventive and therapeutic measures are essential to decrease morbidity, mortality, and cost. Timely recognition and diagnosis of AKI requires a heightened degree of suspicion in the appropriate clinical and environmental context. In low- and middle-income countries (LMICs), early detection is impaired by limited resources and low awareness. In this article, we report the consensus recommendations of the 18th Acute Dialysis Quality Initiative meeting in Hyderabad, India, on how to improve recognition of AKI. We expect these recommendations will lead to an earlier and more accurate diagnosis of AKI, and improved research to promote a better understanding of the epidemiology, etiology, and histopathology of AKI in LMICs.

Profiling of Kidney Injury Biomarkers in Patients Receiving Cisplatin: Time-dependent Changes in the Absence of Clinical Nephrotoxicity

The success of cisplatin-containing regimens to treat solid tumors is limited, in part, by nephrotoxicity. In rodents, several urinary proteins have emerged that are sensitive indicators of cisplatin-induced kidney injury. We sought to characterize time-dependent changes in the urinary concentrations of 12 proteins, including kidney injury molecule-1 (KIM-1), calbindin, beta 2-microglobulin (β2M), and trefoil factor 3 (TFF3) after cisplatin therapy. Urine was collected at baseline, 3 days (range, 2-5 days), and 10 days (range, 9-11 days) from 57 patients with solid tumors receiving outpatient cisplatin therapy (≥25 mg/m2 ). Serum creatinine was largely unchanged after cisplatin infusion. However, compared with baseline values, several novel biomarkers were significantly increased in the urine, including β2M, which was threefold higher by day 3 (P < 0.0001). Urinary KIM-1 and TFF3 were elevated twofold by day 10 (P = 0.002 and P = 0.002, respectively), whereas calbindin levels were increased eightfold (P < 0.0001). We report novel time-dependent changes in the urinary excretion of noninvasive markers of subclinical kidney injury after cisplatin treatment.

The intensive care medicine agenda on acute kidney injury

Acute kidney injury (AKI) is a common complication in the critically ill. Current standard of care mainly relies on identification of patients at risk, haemodynamic optimization, avoidance of nephrotoxicity and the use of renal replacement therapy (RRT) in established AKI. The detection of early biomarkers of renal tissue damage is a recent development that allows amending the late and insensitive diagnosis with current AKI criteria. Increasing evidence suggests that the consequences of an episode of AKI extend long beyond the acute hospitalization. Citrate has been established as the anticoagulant of choice for continuous RRT. Conflicting results have been published on the optimal timing of RRT and on the renoprotective effect of remote ischaemic preconditioning. Recent research has contradicted that acute tubular necrosis is the common pathology in AKI, that septic AKI is due to global kidney hypoperfusion, that aggressive fluid therapy benefits the kidney, that vasopressor therapy harms the kidney and that high doses of RRT improve outcome. Remaining uncertainties include the impact of aetiology and clinical context on pathophysiology, therapy and prognosis, the clinical benefit of biomarker-driven interventions, the optimal mode of RRT to improve short- and long-term patient and kidney outcomes, the contribution of AKI to failure of other organs and the optimal approach for assessing and promoting renal recovery. Based on the established gaps in current knowledge the trials that must have priority in the coming 10 years are proposed together with the definition of appropriate clinical endpoints.

Renal Replacement Therapy in Acute Kidney Injury: Controversies and Consensus

Acute kidney injury (AKI) is a common complication among critically ill patents, and 5% of intensive care unit (ICU) patients require initiation of renal replacement therapy (RRT). In recent years, clinical trials have provided evidence-based guidance for some important aspects of RRT management in patients with AKI, such as dialysis dosing and approaches to anticoagulation in patients undergoing continuous RRT. However, there remain many areas of uncertainty, and delivery of RRT in the ICU requires clinical judgment, flexibility, and an understanding of dialysis principles. This article reviews the components of RRT prescription and provides an update on best practices.

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.

Erythrocyte superoxide dismutase as a biomarker of septic acute kidney injury

Background

Oxidative stress is a key feature of sepsis and could be a common pathophysiological pathway between septic shock and acute kidney injury (AKI) Our objective was to evaluate the erythrocyte superoxide dismutase (SOD1) activity as predictor of AKI in patients with septic shock.

Methods

This is a prospective observational study that evaluated 175 consecutive patients over the age of 18 years with septic shock upon intensive care unit (ICU) admission. However, 43 patients were excluded (27 due to AKI at ICU admission). Thus, 132 patients were enrolled in the study. At the time of the patients’ enrollment, demographic information was recorded. Blood samples were taken within the first 24 h of the patient’s admission to determine the erythrocyte SOD1 activity. All patients were followed throughout the ICU stay, and the development of AKI was evaluated. In addition, we also evaluated 17 control subjects.

Results

The mean age of patients with septic shock was 63.2 ± 15.7 years, 53 % were male and the median ICU stay was 8 days (4–16). Approximately 50.7 % developed AKI during the ICU stay. The median erythrocyte SOD1 activity was 2.92 (2.19–3.92) U/mg Hb. When compared to control subjects, septic shock patients had a higher serum malondialdehyde concentration and lower erythrocyte SOD1 activity. In univariate analysis, erythrocyte SOD1 activity was lower in patients who developed AKI. The ROC curve analysis revealed that lower erythrocyte SOD1 activity was associated with AKI development (AUC 0.686; CI 95 % 0.595–0.777; p < 0.001) at the cutoff of <3.32 U/mg Hb. In the logistic regression models, SOD1 activity higher than 3.32 U/mg Hb was associated with protection of AKI development when adjusted by hemoglobin, phosphorus and APACHE II score (OR 0.309; CI 95 % 0.137–0.695; p = 0.005) and when adjusted by age, gender, chronic kidney disease, admission category (medical or surgery) and APACHE II score (OR 0.129; CI 95 % 0.033–0.508; p = 0.003).

Conclusions

In conclusion, our data suggest that erythrocyte SOD1 activity could play a role as an early marker of septic AKI and could be seen as a new research avenue in the field of biomarker in AKI. However, our study did not show a strong correlation between SOD activity and AKI. Nevertheless, these original data do warrant further research in order to confirm or not this hypothesis.

Kidney Disease and the Nexus of Chronic Kidney Disease and Acute Kidney Injury: The Role of Novel Biomarkers as Early and Accurate Diagnostics

Chronic kidney disease (CKD) and acute kidney injury (AKI) are interconnected and the presence of one is a risk for the other. CKD is an important predictor of AKI after exposure to nephrotoxic drugs or major surgery, whereas persistent or repetitive injury could result in the progression of CKD. This brings new perspectives to the diagnosis and monitoring of kidney diseases highlighting the need for a panel of kidney-specific biomarkers that reflect functional as well as structural damage and recovery, predict potential risk and provide prognosis. This article discusses the kidney-specific biomarkers, symmetric dimethylarginine (SDMA), clusterin, cystatin B, and inosine.

The cell cycle biomarkers: promising research, but do not oversell them

This review focuses on the most recent scientific and clinical information on the development and clinical applicability of the cell cycle biomarkers TIMP-2 and IGFBP-7 in the diagnosis and prognosis of patients at risk for and suffering from acute kidney injury (AKI). A number of evaluation studies have demonstrated that compared with existing biomarkers, urinary excretion of the product of both biomarkers, [TIMP-2]•[IGFBP-7], improved diagnostic performance in assessing the risk for AKI, predicting the need for renal replacement therapy, AKI-related complications and short- and long-term prognoses. The reference intervals for these biomarkers, measured by the recently approved NephroCheck test, have been determined in apparently healthy adults and those with stable chronic morbid conditions without AKI. This review recognizes that the combination of these two cell cycle arrest markers for the early detection of AKI is promising but concludes that its clinical impact is still unproved. Clinicians should understand the utility and limitations of this test before deciding whether to make it available at their institution.