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1.  Human miRNome Profiling Identifies MicroRNAs Differentially Present in the Urine after Kidney Injury 
Clinical chemistry  2013;59(12):10.1373/clinchem.2013.210245.
Extracellular microRNAs (miRNAs) have been proposed as potentially robust and stable biomarkers of various disease conditions. The primary objective of this study was to identify miRNAs differentially occurring in the urine that could serve as potential biomarkers of acute kidney injury (AKI), because traditional AKI markers have limitations with respect to sensitivity, specificity, and timeliness of diagnosis.
We profiled 1809 miRNAs in pooled urine samples from 6 patients with AKI and from 6 healthy controls. We measured the 378 stably detectable miRNAs in the 12 samples individually and selected the top 7 miRNAs that were most different in the urine of patients with AKI compared with the non-AKI control individuals. These miRNAs were assessed in a larger cohort of patients with AKI (n = 98:71 AKI patients in the intensive care unit (ICU) and 27 kidney transplantation patients with biopsy-proven tubular injury) and patients without AKI (n = 97: 74 healthy volunteers and 23 ICU patients without AKI).
We identified 4 miRNAs capable of significantly differentiating patients with AKI from individuals without AKI: miR-21 (P = 0.0005), miR-200c (P < 0.0001), miR-423 (P = 0.001), and miR-4640 (P = 0.0355). The combined cross-validated area under the ROC curve for these 4 miRNAs was 0.91. The imprecision with respect to miRNA isolation and reverse transcription efficiency was <9% across 224 samples.
In this study we determined the entire miRNome of human urine and identified a panel of miRNAs that are both detectable noninvasively and diagnostically sensitive indicators of kidney damage.
PMCID: PMC3870155  PMID: 24153252
2.  Implementation of Novel Biomarkers in the Diagnosis, Prognosis, and Management of Acute Kidney Injury: Executive Summary from the Tenth Consensus Conference of the Acute Dialysis Quality Initiative (ADQI) 
Contributions to nephrology  2013;182:10.1159/000349962.
Detection of acute kidney injury is undergoing a dynamic revolution of biomarker technology allowing greater, earlier, and more accurate determination of diagnosis, prognosis, and with powerful implication for management. Biomarkers can be broadly considered as any measurable biologic entity or process that allows differentiation between normal function and injury or disease. The ADQI (Acute Dialysis Quality Initiative) had its Ninth Consensus Conference dedicated to synthesis and formulation of the existing literature on biomarkers for the detection of acute kidney injury in a variety of settings. In the papers that accompany this summary, ADQI workgroups fully develop key concepts from a summary of the literature in the domains of early diagnosis, differential diagnosis, prognosis and management, and concurrent physiologic and imaging measures.
PMCID: PMC3856225  PMID: 23689652
3.  Serum Cystatin C– Versus Creatinine-Based Definitions of Acute Kidney Injury Following Cardiac Surgery: A Prospective Cohort Study 
The primary aim of this study was to compare the sensitivity and rapidity of AKI detection by cystatin C relative to creatinine following cardiac surgery.
Study Design
Prospective cohort study
Settings and Participants
1,150 high-risk, adult cardiac surgery patients in the TRIBE-AKI (Translational Research Investigating Biomarker Endpoints for Acute Kidney Injury) Consortium.
Changes in serum creatinine and cystatin C
Post-surgical incidence of AKI
Serum creatinine and cystatin C were measured at the preoperative visit and daily on postoperative days 1–5. To allow comparisons between changes in creatinine and cystatin C, AKI endpoints were defined by the relative increases in each marker from baseline (25, 50 and 100%) and the incidence of AKI was compared based upon each marker. Secondary aims were to compare clinical outcomes among patients defined as having AKI by cystatin C and/or creatinine.
Overall, serum creatinine detected more cases of AKI than cystatin C: 35% developed a ≥25% increase in serum creatinine, whereas only 23% had ≥25% increase in cystatin C (p < 0.001). Creatinine also had higher proportions meeting the 50% (14% and 8%, p<0.001) and 100% (4% and 2%, p=0.005) thresholds for AKI diagnosis. Clinical outcomes were generally not statistically different for AKI cases detected by creatinine or cystatin C. However, for each AKI threshold, patients with AKI confirmed by both markers had significantly higher risk of the combined mortality/dialysis outcome compared with patients with AKI detected by creatinine alone (p=0.002).
There were few adverse clinical outcomes, limiting our ability to detect differences in outcomes between subgroups of patients based upon their definitions of AKI.
In this large multicenter study, we found that cystatin C was less sensitive for AKI detection compared with creatinine. However, confirmation by cystatin C appeared to identify a subset of AKI patients with substantially higher risk of adverse outcomes.
PMCID: PMC3496012  PMID: 22809763
4.  The Effects of Heart Failure on Renal Function 
Cardiology clinics  2010;28(3):453-465.
Heart-kidney interactions have been increasingly recognized by clinicians and researchers involved in the study and treatment of heart failure and kidney disease. A classification system has been developed to categorize the different manifestations of cardiac and renal dysfunction. Recent work has highlighted the significant negative prognostic effect of worsening renal function on outcomes for individuals with heart failure. The etiology of the concomitant cardiac and renal dysfunction remains unclear; however, increasing evidence supports alternatives to the established theory of underfilling, including effects of venous congestion and changes in intra-abdominal pressure. Conventional therapy focuses on blockade of the renin-angiotensin-aldosterone system with expanding use of direct renin and aldosterone antagonists. Novel therapeutic interventions using extracorporeal therapy and antagonists of the adenosine pathway show promise and require further investigation.
PMCID: PMC2904358  PMID: 20621250
Cardiorenal; decompensated heart failure; acute kidney injury; management; prognosis
5.  Pre-Operative Serum Brain Natriuretic Peptide and Risk of Acute Kidney Injury after Cardiac Surgery 
Circulation  2012;125(11):1347-1355.
Acute kidney injury (AKI) following cardiac surgery is associated with poor outcomes and is difficult to predict. We conducted a prospective study to evaluate whether pre-operative brain natriuretic peptide (BNP) levels predict postoperative AKI among patients undergoing cardiac surgery.
Methods and Results
The TRIBE-AKI Consortium enrolled 1,139 adults undergoing cardiac surgery at six hospitals from 2007–2009, who were selected for high AKI risk. Pre-operative BNP was categorized into quintiles. AKI was common using Acute Kidney Injury Network definitions; at least mild AKI was a ≥0.3mg/dL or 50% rise in creatinine, n=407 (36%), and severe AKI was either a doubling of creatinine or the requirement of acute renal replacement therapy, n=58 (5.1%). In analyses adjusted for pre-operative characteristics, pre-operative BNP was a strong and independent predictor of mild and severe AKI. Compared with the lowest BNP quintile the highest quintile had significantly higher risk of at least mild AKI (risk ratio [RR] 1.87; 1.40–2.49) and severe AKI (RR 3.17; 1.06–9.48). After adjustment for clinical predictors, addition of BNP improved the area under the curve to predict at least mild AKI (0.67 to 0.69, p=0.02) and severe AKI (0.73 to 0.75, p=0.11). Compared with clinical parameters alone, BNP modestly improved risk prediction of AKI cases into lower and higher risk (continuous net reclassification index at least mild AKI 0.183; 0.061, 0.314; severe AKI 0.231; 0.067, 0.506).
Pre-operative BNP level is associated with post-operative AKI in high-risk patients undergoing cardiac surgery. If confirmed in other types of patients and surgeries, pre-operative BNP may be a valuable component of future efforts to improve pre-operative risk stratification and discrimination among surgical candidates.
PMCID: PMC3312808  PMID: 22322531
brain natriuretic peptide; cardiac surgery; acute renal failure; creatinine
6.  Autologous Creatinine Clearance in a Case of Necrotizing Fasciitis and Anuria 
American Journal of Nephrology  2012;35(3):225-229.
Necrotizing fasciitis can present with concomitant acute kidney injury. The etiology of acute kidney injury is often multifactorial; potential sources include volume depletion, abdominal compartment syndrome, rhabdomyolysis, and acute tubular necrosis (which may be related to hemodynamic instability, medications, or sepsis/infection). Kidney injury, defined via changes in serum creatinine, portends increased morbidity and mortality. Thus, it is crucial to accurately diagnose and assess the severity of kidney injury. We present the case of a patient with necrotizing fasciitis who endured 31 consecutive days of complete anuria. His serum creatinine decreased over this interval without the use of extracorporeal hemofiltration or dialysis. The explanation for this novel phenomenon lies in massive daily sero-sanguineous discharge and insensible losses with subsequent volume resuscitation. The patient's own convective clearance was substantial enough to maintain a modest creatinine clearance of 15 ml/min during sustained anuria. Our case emphasizes the importance of employing the creatinine, estimated glomerular filtration rate, and urine output portions of the Acute Kidney Injury Network (AKIN) or Risk Injury Failure Loss End stage (RIFLE) criteria in assessing the severity of kidney injury. It further reinforces the imperfection in using serum creatinine as a primary measure of glomerular filtration rate.
PMCID: PMC3711005  PMID: 22343604
Necrotizing soft tissue infection; Fasciitis; Acute renal failure; Burn; Debridement
7.  Presurgical Serum Cystatin C and Risk of Acute Kidney Injury After Cardiac Surgery 
Acute kidney injury (AKI) following cardiac surgery is associated with poor outcomes, but is challenging to predict from information available prior to surgery.
Study Design
Prospective cohort study
Setting & Participants
The TRIBE-AKI Consortium enrolled 1,147 adults undergoing cardiac surgery at six hospitals from 2007–2009; participants were selected for high AKI risk.
Pre-surgical cystatin C, creatinine, and creatinine-based estimated glomerular filtration rate (eGFR) were categorized into quintiles and grouped as ‘Best’ (quintiles 1–2), ‘Intermediate’ (quintiles 3–4), and ‘Worst’ (quintile 5) kidney function.
The primary outcome was AKI Network (Acute Kidney Injury Network) Stage 1 or higher; ≥0.3mg/dL or 50% rise in creatinine.
Analyses were adjusted for characteristics used clinically for pre-surgical risk stratification.
The average age and kidney function were: 71±10 years (mean ± standard deviation), serum creatinine 1.1±0.3 mg/dL, eGFR-Cr, 74±9 mL/min/1.73m2, and cystatin C, 0.9 ±0.3 mg/L. A total of 407 (36%) participants developed AKI during hospitalization. Adjusted odds ratios for intermediate and worst kidney function by cystatin C were 1.9 (95% CI, 1.4–2.7) and 4.8 (95% CI, 2.9–7.7) compared with 1.2 (95% CI, 0.9–1.7) and 1.8 (95% CI, 1.2–2.6) for creatinine and 1.0 (95% CI, 0.7–1.4) and 1.7 (95% CI, 1.1–2.3) for eGFR-Cr categories, respectively. After adjustment for clinical predictors, the C statistic to predict AKI was 0.70 without kidney markers, 0.69 with creatinine, and 0.72 with cystatin C. Cystatin C also substantially improved AKI risk classification compared to creatinine, based on a net reclassification index of 0.21 (p<0.001).
The ability of these kidney biomarkers to predict risk for dialysis-requiring AKI or death could not be reliably assessed in our study due to a small number of patients with either outcome.
Pre-surgical cystatin C is better than creatinine or creatinine-based eGFR at forecasting the risk of AKI after cardiac surgery.
PMCID: PMC3159705  PMID: 21601336
acute renal failure; creatinine; prognosis
8.  Urine Cystatin C as a Biomarker of Proximal Tubular Function Immediately after Kidney Transplantation 
American Journal of Nephrology  2011;33(5):407-413.
Clinical methods to predict allograft function soon after kidney transplantation are ineffective.
We analyzed urine cystatin C (CyC) in a prospective multicenter observational cohort study of deceased-donor kidney transplants to determine its peritransplant excretion pattern, utility for predicting delayed graft function (DGF) and association with 3-month graft function. Serial urine samples were collected for 2 days following transplant and analyzed blindly for CyC. We defined DGF as any hemodialysis in the first week after transplant, slow graft function (SGF) as a serum creatinine reduction <70% by the first week and immediate graft function (IGF) as a reduction ≥70%.
Of 91 recipients, 33 had DGF, 34 had SGF and 24 had IGF. Urine CyC/urine creatinine was highest in DGF for all time-points. The area under the curve (95% CI) for predicting DGF at 6 h was 0.69 (0.57–0.81) for urine CyC, 0.74 (0.62–0.86) for urine CyC/urine creatinine and 0.60 (0.45–0.75) for percent change in urine CyC. On the first postoperative day, urine CyC/urine creatinine and percent change in urine CyC were associated with 3-month graft function.
Urine CyC on the day after transplant differs between degrees of perioperative graft function and modestly corresponds with 3-month function.
PMCID: PMC3100377  PMID: 21494031
Transplantation; Biomarkers; Ischemia/reperfusion; Outcomes
9.  Mechanical Ventilation and the Kidney 
Blood Purification  2009;29(1):52-68.
Acute lung injury (ALI) and acute kidney injury (AKI) are complications often encountered in the setting of critical illness. Both forms of end-organ injury commonly occur in similar settings of systemic inflammatory response syndrome, shock, and evolving multiple organ dysfunction. Recent elucidation of the pathobiology of critical illness has led to a more basic mechanistic understanding of the complex interplay between injured organs in patients with multiple organ dysfunction syndrome; this has been aptly called ‘the slippery slope of critical illness’ [Kidney Int Suppl 1998;66:S25–S33]. Distant organ effects of apparently isolated injuries to the lungs, gut, and kidneys have all been discovered in recent years. In this article, we will review the harmful bidirectional interaction between ALI and AKI, which appears to be a common clinical syndrome with routine clinical implications. We will review the current understanding of lung-kidney interactions from both perspectives, including the renal effects of ALI and mechanical ventilation, and the pulmonary sequelae of AKI. In this review of the emerging evidence of deleterious bidirectional organ cross talk between lung and kidney, we will focus on the role of ventilator-induced kidney injury in the pathogenesis of AKI in patients with ALI.
PMCID: PMC2914396  PMID: 19923815
Acute kidney injury; Critical care nephrology; Acute lung injury; Mechanical ventilation; Cytokines
10.  Urinary cystatin C as an early biomarker of acute kidney injury following adult cardiothoracic surgery 
Kidney international  2008;74(8):1059-1069.
There is a need to develop early biomarkers of acute kidney injury following cardiac surgery, where morbidity and mortality are increased by its presence. Plasma cystatin C (CyC) and plasma and urine Neutrophil Gelatinase Associated Lipocalin (NGAL) have been shown to detect kidney injury earlier than changes in plasma creatinine in critically ill patients. In order to determine the utility of urinary CyC levels as a measure of kidney injury, we prospectively collected plasma and urine from 72 adults undergoing elective cardiac surgery for analysis. Acute kidney injury was defined as a 25% or greater increase in plasma creatinine or renal replacement therapy within the first 72 hours following surgery. Plasma CyC and NGAL were not useful predictors of acute kidney injury within the first 6 hours following surgery. In contrast, both urinary CyC and NGAL were elevated in the 34 patients who later developed acute kidney injury, compared to those with no injury. The urinary NGAL at the time of ICU arrival and the urinary CyC level 6 hours after ICU admission were most useful for predicting acute kidney injury. A composite time point consisting of the maximum urinary CyC achieved in the first 6 hours following surgery outperformed all individual time points. Our study suggests that urinary CyC and NGAL are superior to conventional and novel plasma markers in the early diagnosis of acute kidney injury following adult cardiac surgery.
PMCID: PMC2745082  PMID: 18650797
cystatin C; acute kidney injury; biomarker; cardiac surgery; Neutrophil Gelatinase Associated Lipocalin

Results 1-10 (10)