Neutrophil Gelatinase-Associated Lipocalin as an Early Sign of Diabetic Kidney Injury in Children

Objective:

There is some evidence indicating that histopathological changes in type 1 diabetes mellitus (T1DM) emerge before onset of microalbuminuria. The aim of our study was to determine whether urine neutrophil gelatinase-associated lipocalin (NGAL) levels can be considered as an early sign of diabetic kidney injury.

Methods:

Urine NGAL (uNGAL) levels and urinary NGAL/creatinine ratio (uNGAL/Cr) were assessed in 76 patients with T1DM and compared with the findings of 35 healthy individuals. The relationship of uNGAL levels with diabetes duration, body mass index (BMI), serum lipids, HbA1c, and microalbuminuria was also evaluated.

Results:

Mean uNGAL (100.16±108.28 ng/mL) and uNGAL/Cr (118.93-117.97 ng/mg) levels in both microalbuminuric and non-microalbuminuric diabetic patients were found to be higher than those in the control group (uNGAL: 21.46±18.59 ng/mL and uNGAL/Cr: 32.1±51.48 ng/mg) (p=0.0001).

Conclusion:

Urine NGAL level increases in the very early phase of T1DM before microalbuminuria develops. The patients with T1DM should be considered to have diabetic kidney injury from the time of diagnosis on and preventive interventions need to be initiated at an early stage to preclude the progression to end-stage renal disease.     

Modality of RRT and Recovery of Kidney Function after AKI in Patients Surviving to Hospital Discharge

Background and objectives

Observational evidence has suggested that RRT modality may affect recovery after AKI. It is unclear whether initial choice of intermittent hemodialysis or continuous RRT affects renal recovery, survival, or development of ESRD in critically ill patients when modality choice is made primarily on hemodynamics.

Design, setting, participants, & measurements

We performed a retrospective cohort study examining adults (≥18 years old) admitted to intensive care units from 2000 to 2008 who received RRT for AKI and survived to hospital discharge or 90 days. We analyzed renal recovery (alive and not requiring RRT) and reasons for nonrecovery (death or ESRD) at 90 and 365 days. Conditional multivariable logistic regression was used to assess differences in renal recovery at 90 and 365 days between continuous RRT and intermittent hemodialysis. Models were stratified by propensity for continuous RRT and adjusted for age and reference creatinine.

Results

Of 4738 patients with Kidney Disease Improving Global Outcomes stage 3 AKI, 1338 (28.2%) received RRT, and 638 (47.7%) survived to hospital discharge (353 intermittent hemodialysis and 285 continuous RRT). Recovery from AKI was lower for intermittent hemodialysis versus continuous RRT at 90 days (66.6% intermittent hemodialysis versus 75.4% continuous RRT; P=0.02) but similar at 365 days (54.1% intermittent hemodialysis versus 59.6% continuous RRT; P=0.17). In multivariable analysis, there was no difference in odds of recovery at 90 or 365 days for patients initially treated with continuous RRT versus intermittent hemodialysis (90 days: odds ratio, 1.19; 95% confidence interval, 0.91 to 1.55; P=0.20; 365 days: odds ratio, 0.93; 95% confidence interval, 0.72 to 1.2; P=0.55).

Conclusions

We found no significant difference in hazards for nonrecovery or reasons for nonrecovery (mortality or ESRD) with intermittent hemodialysis versus continuous RRT. These results suggest that, when initial RRT modality is chosen primarily on hemodynamics, renal recovery and clinical outcomes in survivors are similar between intermittent hemodialysis and continuous RRT.     

Incorporation of Biomarkers with the Renal Angina Index for Prediction of Severe AKI in Critically Ill Children

Background and objectives

Novel AKI biomarkers carry variable performance for prediction of AKI in patients with heterogeneous illness. Until utility is demonstrated in critically ill patients outside of the cardiopulmonary bypass population, AKI biomarkers are unlikely to gain widespread implementation. Operationalization of an AKI risk stratification methodology, termed renal angina, was recently reported to enhance prediction at the time of intensive care unit admission for persistent severe AKI. The renal angina index (RAI) was developed to provide the clinical context to direct AKI biomarker testing. This study tested the hypothesis that incorporation of AKI biomarkers in patients fulfilling renal angina improves the prediction of persistent severe AKI.

Design, setting, participants, & measurements

In a multicenter study of 214 patients admitted to the pediatric intensive care unit with sepsis, the discrimination of plasma neutrophil gelatinase–associated lipocalin (NGAL), matrix metalloproteinase-8 (MMP-8), and neutrophil elastase-2 (Ela-2) were determined individually and in combination with the RAI for severe AKI. Net reclassification improvement (NRI) and integrated discrimination improvement (IDI) were calculated.

Results

Individual biomarkers demonstrated marginal discrimination for severe AKI (area under curve [AUC]: NGAL, 0.72; MMP-8, 0.68; Ela-2, 0.72), inferior to prediction by the clinical model of the RAI (AUC=0.80). Incorporation of each biomarker significantly added to the renal angina model AKI prediction (AUC=0.80, increased to 0.84–0.88; P<0.05 for each). The inclusion of each biomarker with the RAI demonstrated NRI (0.512, 0.428, and 0.545 for NGAL, MMP-8, and Ela-2, respectively; all P<0.03) and IDI (0.075 for Ela-2). The inclusion of both Ela-2 and NGAL with RAI demonstrated an NRI of 0.871 (P<0.001) and an IDI of 0.1 (P=0.01).

Conclusions

This study shows that incorporation of AKI biomarkers into the RAI improves discrimination for severe AKI. The RAI optimizes the utility of AKI biomarkers in a heterogeneous, critically ill patient population.     

Improvement in the Renal Prognosis in Nephropathic Cystinosis

Summary

Background and objectives

Nephropathic cystinosis (NC) is an autosomal recessive disorder occurring in one to two per 100,000 newborns. Because of the rarity of NC, long-term outcome data are scarce.

Design, setting, participants, & measurements

245 NC patients from 18 countries provided data to the ESPN/ERA-EDTA registry. We matched NC patients on renal replacement therapy (RRT) to non-NC children on RRT.

Results

Between 1979 and 2008, mean age at the start of RRT among NC children increased by 0.15 year per calendar year (95% confidence interval, 0.10 to 0.21) from 8.8 to 12.7 years, whereas we did not observe this in non-NC children. Five-year survival after the start of RRT improved in NC patients from 86.1% (before 1990) to 100% (since 2000) as compared with the control population (89.6% and 94.0%). NC patients received a renal allograft more often (relative risk, 1.09; 95% confidence interval, 1.00 to 1.17) as compared with matched RRT children, and 5-year graft survival was better (94.0% versus 84.0%). NC dialysis patients were less often hypertensive than non-NC children matched for age, country, and dialysis modality (42.7% versus 51.7%) and had lower parathyroid hormone levels (median, 56 versus 140 pg/ml). Although height at start of RRT slightly improved during the past decade, children with NC remained significantly shorter than non-NC children at the start of RRT.

Conclusions

We demonstrated improved survival of the renal function as well as better patient and graft survival after the start of RRT in a large European cohort of NC patients over the last two decades.     

Renal Outcomes in Critically Ill Patients Receiving Propofol or Midazolam

Background and objectives

Propofol has been shown to provide protection against renal ischemia/reperfusion injury experimentally, but clinical evidence is limited to patients undergoing cardiac surgery. There are no data about its association with oliguria and AKI in critically ill patients.

Design, setting, participants, & measurements

We obtained data from the Multiparameter Intelligent Monitoring in Intensive Care II database (2001–2008). Patient selection criteria included adult patients in their first intensive care unit (ICU) admission, need for mechanical ventilation, and treatment with propofol or midazolam. Propensity score analysis (1:1) was used and renal-related outcomes (AKI, oliguria, cumulative fluid balance, and need for RRT) were evaluated during the first 7 days of ICU stay.

Results

There were 1396 propofol/midazolam-matched patients. AKI in the first 7-day ICU time period was statistically lower in propofol-treated patients compared with midazolam-treated patients (55.0% versus 67.3%, P<0.001). Propofol was associated with lower AKI incidence using both urine output (45.0% versus 55.7%, P<0.001) and serum creatinine criteria (28.8% versus 37.2%, P=0.001). Patients receiving propofol had oliguria (<400 ml/d) less frequently (12.4% versus 19.6%, P=0.001) and had diuretics prescribed less often (8.5% versus 14.3%, P=0.001). In addition, during the first 7 days of ICU stay, patients receiving propofol less frequently achieved cumulative fluid balance >5% of body weight (50.1% versus 58.3%, P=0.01). The need for RRT in the first 7 days of ICU stay was also less frequent in propofol-treated patients (3.4% versus 5.9%, P=0.03). ICU mortality was lower in propofol-treated patients (14.6% versus 29.7%, P<0.001).

Conclusions

In this large, propensity-matched ICU population, patients treated with propofol had a lower risk of AKI, fluid-related complications, and need for RRT.     

Kinetic eGFR and Novel AKI Biomarkers to Predict Renal Recovery

Background and objectives

Prompt recognition of severe renal impairment could improve the early management of critically ill patients. We compared the value of kinetic eGFR, plasma neutrophil gelatinase–associated lipocalin (NGAL), and urine tissue inhibitor of metalloproteinase-2 and urine insulin-like growth factor–binding protein 7 ([TIMP-2]*[IGFBP7]) in predicting short-term recovery from AKI and major adverse kidney events.

Design, setting, participants, & measurements

During the 6-month study period, 245 patients were admitted to our intensive care unit. This study included 57 consecutive patients presenting with AKI within the first 24 hours after admission. AKI markers were evaluated at inclusion (day 0) and 24 hours later (day 1). Kinetic eGFR was calculated on day 1 according to serum creatinine evolution. Renal recovery was defined as normalization of serum creatinine with reversal of oliguria within 48 hours. Major adverse kidney events included death, need for RRT, or persistence of renal dysfunction at hospital discharge.

Results

Plasma NGAL and [TIMP-2]*[IGFBP7] predicted renal recovery, with area under the receiver-operating characteristic curve (AUC-ROC) values between 0.70 and 0.79 at inclusion. Although plasma NGAL values frequently reached the maximal measurement range, their decrease on day 1 predicted recovery. The kinetic eGFR calculation after initial resuscitation provided the best AUC-ROC value for renal recovery, at 0.87. The best predictions for major adverse kidney events were provided by [TIMP-2]*[IGFBP7] and kinetic eGFR (equal AUC-ROCs of 0.81). Combining AKI markers in addition to clinical prediction models improved the discrimination and reclassification of patients who will recover from AKI or suffer from major adverse kidney events.

Conclusions

Biomarkers of kidney damage predicted short-term renal recovery and major adverse kidney events for an unselected cohort of critically ill patients. Calculating the kinetic eGFR imposed a delay after initial resuscitation but provided a good diagnostic and prognostic approach. The utility of functional and damage AKI marker combinations in addition to clinical information requires validation in larger prospective studies.     

Risk of poor outcomes with novel and traditional biomarkers at clinical AKI diagnosis

Summary

Background and objectives

Studies have evaluated acute kidney injury (AKI) using biomarkers in various settings, but their prognostic utility within current practice is unclear. Thus, we sought to determine the prognostic utility of newer biomarkers or traditional markers (fractional excretion of sodium [FeNa] and urea [FeUrea] and microscopy) over clinical assessment alone.

Design, setting, participants, & measurements

This is a prospective cohort study of adults on the first day of meeting AKI criteria. We measured urine concentrations of neutrophil gelatinase-associated lipocalin (NGAL), kidney injury molecule-1 (KIM-1), and IL-18 and determined FeNa, FeUrea, and microscopy score for casts and tubular cells. Primary outcome was worsened AKI stage from enrollment to peak serum creatinine or in-hospital death.

Results

In 249 recipients, 57% were ≥65 years old, 48% were from intensive care, and mean baseline GFR was 69 ± 30 ml/min per 1.73 m². AKI was considered prerenal in 164 (66%), acute tubular necrosis (ATN) in 51 (20%), and “other” in 34 (14%). All mean protein biomarker concentrations, FeNa, FeUrea, and microscopy scores were statistically different between prerenal and ATN. Seventy-two patients (29%) developed the primary outcome. There was an approximate three-fold increase in adjusted risk for the outcome for upper versus lower values of NGAL, KIM-1, IL-18, and microscopy score (P values <0.05). Net reclassification improved after adding these to baseline clinical assessment. FeNa and FeUrea were not useful.

Conclusions

On the first day of AKI, urine protein biomarkers and microscopy significantly improve upon clinical determination of prognosis, indicating their potential utility in current practice.     

Renal Arcuate Vein Microthrombi-Associated AKI

Backgrounds and objectives

This report describes six patients with AKI stages 2–3 (median admission creatinine level, 2.75 mg/dl [range, 1.58–5.44 mg/dl]), hematuria (five with hemoproteinuria), and unremarkable imaging with an unusual and unexplained histologic diagnosis on renal biopsy.

Design, setting, participants, & measurements

The patients were young adults who presented to two neighboring United Kingdom nephrology centers over a 40-month period (between July 2010 and November 2013). Four were male, and the median age was 22.5 years (range, 18–27 years). Their principal symptoms were flank pain or lower back pain. All had consumed alcohol in the days leading up to admission.

Results

Renal biopsy demonstrated microthrombi in the renal arcuate veins with a corresponding stereotypical, localized inflammatory infiltrate at the corticomedullary junction. All patients recovered to baseline renal function with supportive care (median, 17 days; range, 6–60 days), and none required RRT. To date, additional investigations have not revealed an underlying cause for these histopathologic changes. Investigations have included screening for thrombophilic tendencies, renal vein Doppler ultrasonographic studies, and testing for recreational drugs and alcohol (including liquid chromatography–mass spectrometry of urine) to look for so-called designer drugs. Inquiries to the United Kingdom National Poisons Information Centre have identified no other cases with similar presentation or histologic findings.

Conclusions

Increased awareness and additional study of future cases may lead to a greater understanding of the underlying pathophysiologic mechanisms that caused AKI in these patients.     

Associations between Intensity of RRT,Inflammatory Mediators,and Outcomes

Background and objectives

Critically ill patients requiring RRT have higher circulating plasma concentrations of inflammatory and apoptosis markers that are associated with subsequent RRT dependence and death. Whether intensive dosing of RRT is associated with changes in specific mediators is unknown.

Design, setting, participants, & measurements

A multicenter, prospective, cohort study of 817 critically ill patients receiving RRT ancillary to the Veterans Affairs/National Institutes of Health Acute Renal Failure Trial Network study was conducted between November 2003 and July 2007. Plasma inflammatory (IL-6, IL-8, IL-10, IL-18, and macrophage migration inhibitory factor) and apoptosis (TNF receptor-I [TNFR-I], TNFR-II, and death receptor-5) biomarkers on days 1 and 8 were examined after initiation of intensive RRT. Whether intensive RRT, given day 1 biomarkers, is associated with RRT independence and lower mortality at day 60 was also examined.

Results

Overall, no differences were found in day 8 biomarker concentrations between intensive and less-intensive RRT groups. When adjusted for day 1 biomarkers and clinical variables, intensive RRT was not associated with renal recovery (adjusted odds ratio [OR], 0.80; 95% confidence interval, 0.56 to 1.14) or mortality (adjusted OR, 1.15; 95% confidence interval, 0.81 to 1.64). Use of intensive RRT, however, was associated with lower day 8 concentrations when day 1 plasma IL-6, macrophage migration inhibitory factor, and TNFR-I concentrations were high (interaction P value for all markers, <0.01). In contrast, day 8 marker concentrations were higher when day 1 levels were low (P<0.01). Elevated biomarker concentrations on day 8 among 476 participants were associated with lower renal recovery (adjusted OR range, 0.19–0.87) and higher mortality (adjusted OR range, 1.26–3.18).

Conclusions

Among critically ill patients receiving RRT, intensive dosing of RRT has variable association with biomarker concentration and no association with renal recovery and mortality. However, elevated concentrations of inflammatory and apoptosis markers on day 8 of RRT were associated with RRT dependence and death.     

Follow-Up Renal Assessment of Injury Long-Term After Acute Kidney Injury (FRAIL-AKI)

Background and objectives

Novel urinary kidney damage biomarkers detect AKI after cardiac surgery using cardiopulmonary bypass (CPB-AKI). Although there is growing focus on whether AKI leads to CKD, no studies have assessed whether novel urinary biomarkers remain elevated long term after CPB-AKI. We assessed whether there was clinical or biomarker evidence of long-term kidney injury in patients with CPB-AKI.

Design, setting, participants, & measurements

We performed a cross-sectional evaluation for signs of chronic kidney injury using both traditional measures and novel urinary biomarkers in a population of 372 potentially eligible children (119 AKI positive and 253 AKI negative) who underwent surgery using cardiopulmonary bypass for congenital heart disease at Cincinnati Children’s Hospital Medical Center between 2004 and 2007. A total of 51 patients (33 AKI positive and 18 AKI negative) agreed to long-term assessment. We also compared the urinary biomarker levels in these 51 patients with those in healthy controls of similar age.

Results

At long-term follow-up (mean duration±SD, 7±0.98 years), AKI-positive and AKI-negative patients had similarly normal assessments of kidney function by eGFR, proteinuria, and BP measurement. However, AKI-positive patients had higher urine concentrations of IL-18 (48.5 pg/ml versus 20.3 pg/ml [P=0.01] and 20.5 pg/ml [P<0.001]) and liver-type fatty acid–binding protein (L-FABP) (5.9 ng/ml versus 3.9 ng/ml [P=0.001] and 3.2 ng/ml [P<0.001]) than did AKI-negative patients and healthy controls.

Conclusions

Novel urinary biomarkers remain elevated 7 years after an episode of CPB-AKI in children. However, there is no conventional evidence of CKD in these children. These biomarkers may be a more sensitive marker of chronic kidney injury after CPB-AKI. Future studies are needed to understand the clinical relevance of persistent elevations in IL-18, kidney injury molecule-1, and L-FABP in assessments for potential long-term kidney consequences of CPB-AKI.     

Urinary neutrophil gelatinase-associated lipocalin time course during cardiac surgery

Background:

NGAL is one of the most promising AKI biomarkers in cardiac surgery. However, the best timing to dose it and the reference values are still matter of discussion.

Aim of the Study:

We performed a uNGAL perioperative time course, to better understand its perioperative kinetics and its role in AKI diagnosis.

Setting of the Study:

San Raffaele University Hospital, cardiac surgery department.

Material and Methods:

We enrolled in this prospective observational study 19 patients undergoing cardiac surgery with cardiopulmonary bypass (CPB). Based on preoperative characteristics, they were divided in low-risk and high-risk patients. uNGAL measurements were collected at pre-defined times before, during, and up to 24 hours after surgery.

Statistical Analysis:

Data were analysed by use of SAS 1999-2001 program or IBM SPSS Statistics.

Results:

In low-risk patients, uNGAL had the highest value immediately after general anesthesia induction (basal dosage: uNGAL: 12.20ng×ml^-1, IQR 14.00). It later decreased significantly (3.40 ng×ml^-1, IQR 4.80; P = 0.006) during CPB, and finally return to its original value 24 hours after surgery. In high-risk patients, uNGAL increased immediately after surgery; it had the highest value on ICU arrival (38,20 ng×ml^-1; IQR 133,10) and remained high for several hours. A difference in uNGAL levels between the two groups was already observed at the end of surgery, but it became statistically significant on ICU arrival (P = 0.002).

Conclusion:

This study helps to better understand the different kinetics of this new biomarker in low-risk and high-risk cardiac patients.     

Biomarker Enhanced Risk Prediction for Adverse Outcomes in Critically Ill Patients Receiving RRT

Background and objectives

Higher plasma concentrations of inflammatory and apoptosis markers in critically ill patients receiving RRT are associated with RRT dependence and death. This study objective was to examine whether plasma inflammatory (IL-6, -8, -10, and -18; macrophage migration inhibitory factor) and apoptosis (death receptor-5, tumor necrosis factor receptor I and II) biomarkers augment risk prediction of renal recovery and mortality compared with clinical models.

Design, setting, participants, & measurements

The Biologic Markers of Recovery for the Kidney study (n=817) was a prospective, nested, observational cohort study conducted as an ancillary to the Veterans Affairs/National Institutes of Health Acute renal failure Trial Network study, a randomized trial of intensive versus less intensive RRT in critically ill patients with AKI conducted between November 2003 and July 2007 at 27 Veterans Affairs– and university-affiliated centers. Primary outcomes of interest were renal recovery and mortality at day 60.

Results

A parsimonious clinical model consisting of only four variables (age, mean arterial pressure, mechanical ventilation, and bilirubin) predicted renal recovery (area under the receiver-operating characteristic curve [AUROC], 0.73; 95% confidence interval [95% CI], 0.68 to 0.78) and mortality (AUROC, 0.74; 95% CI, 0.69 to 0.78). By contrast, individual biomarkers were only modestly predictive of renal recovery (AUROC range, 0.55–0.63) and mortality (AUROC range, 0.54–0.68). Adding plasma IL-8 to a parsimonious model augmented prediction of recovery (AUROC, 0.76; 95% CI, 0.71 to 0.81; P=0.04) and mortality (AUROC, 0.78; 95% CI, 0.73 to 0.82; P<0.01) compared with the clinical model alone.

Conclusions

This study suggests that a simple four-variable clinical model with plasma IL-8 had predictive value for renal recovery and mortality. These findings require external validation but could easily be used by clinicians.     

HMG–CoA Reductase Activation and Urinary Pellet Cholesterol Elevations in Acute Kidney Injury

Summary

Background and objectives

Experimental acute kidney injury (AKI) activates the HMG–CoA reductase (HMGCR) gene, producing proximal tubule cholesterol loading. AKI also causes sloughing of proximal tubular cell debris into tubular lumina. This study tested whether these two processes culminate in increased urinary pellet cholesterol content, and whether the latter has potential AKI biomarker utility.

Design, setting, participants, & measurements

Urine samples were collected from 29 critically ill patients with (n = 14) or without (n= 15) AKI, 15 patients with chronic kidney disease, and 15 healthy volunteers. Centrifuged urinary pellets underwent lipid extraction, and the extracts were assayed for cholesterol content (factored by membrane phospholipid phosphate content). In vivo HMGCR activation was sought by measuring levels of RNA polymerase II (Pol II), and of a gene activating histone mark (H3K4m3) at exon 1 of the HMGCR gene (chromatin immunoprecipitation assay of urine chromatin samples).

Results

AKI+ patients had an approximate doubling of urinary pellet cholesterol content compared with control urine samples (versus normal; P < 0.001). The values significantly correlated (r, 0.5; P < 0.01) with serum, but not urine, creatinine concentrations. Conversely, neither critical illness without AKI nor chronic kidney disease raised pellet cholesterol levels. Increased HMGCR activity in the AKI+ patients was supported by three- to fourfold increased levels of Pol II, and of H3K4m3, at the HMGCR gene (versus controls or AKI− patients).

Conclusions

(1) Clinical AKI, like experimental AKI, induces HMGCR gene activation; (2) increased urinary pellet cholesterol levels result; and (3) urine pellet cholesterol levels may have potential AKI biomarker utility. The latter will require future testing in a large prospective trial.     

Relative Performance of the MDRD and CKD-EPI Equations for Estimating Glomerular Filtration Rate among Patients with Varied Clinical Presentations

Summary

Background

The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) equation was developed using both CKD and non-CKD patients to potentially replace the Modification of Diet in Renal Disease (MDRD) equation that was derived with only CKD patients. The objective of our study was to compare the accuracy of the MDRD and CKD-EPI equations for estimating GFR in a large group of patients having GFR measurements for diverse clinical indications.

Design, setting, participants, and measurements

A cross-sectional study was conducted of patients who underwent renal function assessment for clinical purposes by simultaneous measurements of serum creatinine and estimation of GFR using the MDRD and CKD-EPI equations and renal clearance of iothalamate (n = 5238).

Results

Bias compared with measured GFR (mGFR) varied for each equation depending on clinical presentation. The CKD-EPI equation demonstrated less bias than the MDRD equation in potential kidney donors (−8% versus −18%) and postnephrectomy donors (−7% versus −15%). However, the CKD-EPI equation was slightly more biased than the MDRD equation in native CKD patients (6% versus 3%), kidney recipients (8% versus 1%), and other organ recipients (9% versus 3%). Among potential kidney donors, the CKD-EPI equation had higher specificity than the MDRD equation for detecting an mGFR <60 ml/min per 1.73 m² (98% versus 94%) but lower sensitivity (50% versus 70%).

Conclusions

Clinical presentation influences the estimation of GFR from serum creatinine, and neither the CKD-EPI nor MDRD equation account for this. Use of the CKD-EPI equation misclassifies fewer low-risk patients as having reduced mGFR, although it is also less sensitive for detecting mGFR below specific threshold values used to define CKD stages.     

Neutrophil Gelatinase-Associated Lipocalin in the Diagnosis of Type 1 Cardio-Renal Syndrome in the General Ward

Summary

Background and objectives

The early identification of acute heart failure (HF) patients with type 1 cardio-renal syndrome should be the first step for developing prevention and treatment strategies for these patients. This study aimed to assess the performance of neutrophil gelatinase-associated lipocalin (NGAL) and cystatin C in the early detection of type 1 cardio-renal syndrome in patients with acute HF.

Design, setting, participants, & measurements

One-hundred nineteen patients admitted with acute HF were studied. NGAL and creatinine were measured in the first hospitalization morning; creatinine was also measured at least after 48 to 72 hours. Physicians were blinded to NGAL and cystatin C levels. Type 1 cardio-renal syndrome was defined as an increase in the creatinine level of at least 0.3 mg/dl or 50% of basal creatinine.

Results

Type 1 cardio-renal syndrome developed within 48 to 72 hours in 14 patients (11.8%). Admission NGAL levels were higher in these patients: 212 versus 83 ng/dl. At a cutoff value of 170 ng/L, NGAL determined type 1 cardio-renal syndrome with a sensitivity of 100% and a specificity of 86.7%. The area under the receiver-operating characteristic curve of NGAL was 0.93 and that of cystatin C was 0.68.

Conclusions

Above a cutoff value of 170 ng/L, NGAL predicts 48- to 72-hour development of type 1 cardio-renal syndrome with a negative predictive value of 100% and a positive predictive value of 50%. NGAL independently associates with type 1 cardio-renal syndrome and might be a useful biomarker in the early recognition of these patients.     

Platelet Activation in Patients with Atherosclerotic Renal Artery Stenosis Undergoing Stent Revascularization

Summary

Background and objectives

Soluble CD40 ligand (sCD40L) is a marker of platelet activation; whether platelet activation occurs in the setting of renal artery stenosis and stenting is unknown. Additionally, the effect of embolic protection devices and glycoprotein IIb/IIIa inhibitors on platelet activation during renal artery intervention is unknown.

Design, setting, participants, & measurements

Plasma levels of sCD40L were measured in healthy controls, patients with atherosclerosis without renal stenosis, and patients with renal artery stenosis before, immediately after, and 24 hours after renal artery stenting.

Results

Soluble CD40L levels were higher in renal artery stenosis patients than normal controls (347.5 ± 27.0 versus 65.2 ± 1.4 pg/ml, P < 0.001), but were similar to patients with atherosclerosis without renal artery stenosis. Platelet-rich emboli were captured in 26% (9 of 35) of embolic protection device patients, and in these patients sCD40L was elevated before the procedure. Embolic protection device use was associated with a nonsignificant increase in sCD40L, whereas sCD40L declined with abciximab after the procedure (324.9 ± 42.5 versus 188.7 ± 31.0 pg/ml, P = 0.003) and at 24 hours.

Conclusions

Atherosclerotic renal artery stenosis is associated with platelet activation, but this appears to be related to atherosclerosis, not renal artery stenosis specifically. Embolization of platelet-rich thrombi is common in renal artery stenting and is inhibited with abciximab.     

Serum Creatinine Changes Associated with Critical Illness and Detection of Persistent Renal Dysfunction after AKI

Background and objectives

AKI is a risk factor for development or worsening of CKD. However, diagnosis of renal dysfunction by serum creatinine could be confounded by loss of muscle mass and creatinine generation after critical illness.

Design, setting, participants, & measurements

A retrospective, single center analysis of serum in patients surviving to hospital discharge with an intensive care unit admission of 5 or more days between 2009 and 2011 was performed.

Results

In total, 700 cases were identified, with a 66% incidence of AKI. In 241 patients without AKI, creatinine was significantly lower (P<0.001) at hospital discharge than admission (median, 0.61 versus 0.88 mg/dl; median decrease, 33%). In 160 patients with known baseline, discharge creatinine was significantly lower than baseline in all patients except those patients with severe AKI (Kidney Disease Improving Global Outcomes category 3), who had no significant difference. In a multivariable regression model, median duration of hospitalization was associated with a predicted 30% decrease (95% confidence interval, 8% to 45%) in creatinine from baseline in the absence of AKI; after allowing for this effect, AKI was associated with a 29% (95% confidence interval, 10% to 51%) increase in predicted hospital discharge creatinine. Using a similar model to exclude the confounding effect of prolonged major illness on creatinine, 148 of 700 patients (95% confidence interval, 143 to 161) would have eGFR<60 ml/min per 1.73 m² at hospital discharge compared with only 63 of 700 patients using eGFR based on unadjusted hospital creatinine (a 135% increase in potential CKD diagnoses; P<0.001).

Conclusion

Critical illness is associated with significant falls in serum creatinine that persist to hospital discharge, potentially causing inaccurate assessment of renal function at discharge, particularly in survivors of AKI. Prospective measurements of GFR and creatinine generation are required to confirm the significance of these findings.     

Utilization of Small Changes in Serum Creatinine with Clinical Risk Factors to Assess the Risk of AKI in Critically lll Adults

Background and objectives

Disease biomarkers require appropriate clinical context to be used effectively. Combining clinical risk factors, in addition to small changes in serum creatinine, has been proposed to improve the assessment of AKI. This notion was developed in order to identify the risk of AKI early in a patient''s clinical course. We set out to assess the performance of this combination approach.

Design, setting, participants, & measurements

A secondary analysis of data from a prospective multicenter intensive care unit cohort study (September 2009 to April 2010) was performed. Patients at high risk using this combination approach were defined as an early increase in serum creatinine of 0.1–0.4 mg/dl, depending on number of clinical factors predisposing to AKI. AKI was defined and staged using the Acute Kidney Injury Network criteria. The primary outcome was evolution to severe AKI (Acute Kidney Injury Network stages 2 and 3) within 7 days in the intensive care unit.

Results

Of 506 patients, 214 (42.2%) patients had early creatinine elevation and were deemed at high risk for AKI. This group was more likely to subsequently develop the primary endpoint (16.4% versus 1.0% [not at high risk], P<0.001). The sensitivity of this grouping for severe AKI was 92%, the specificity was 62%, the positive predictive value was 16%, and the negative predictive value was 99%. After adjustment for Sequential Organ Failure Assessment score, serum creatinine, and hazard tier for AKI, early creatinine elevation remained an independent predictor for severe AKI (adjusted relative risk, 12.86; 95% confidence interval, 3.52 to 46.97). Addition of early creatinine elevation to the best clinical model improved prediction of the primary outcome (area under the receiver operating characteristic curve increased from 0.75 to 0.83, P<0.001).

Conclusion

Critically ill patients at high AKI risk, based on the combination of clinical factors and early creatinine elevation, are significantly more likely to develop severe AKI. As initially hypothesized, the high-risk combination group methodology can be used to identify patients at low risk for severe AKI in whom AKI biomarker testing may be expected to have low yield. The high risk combination group methodology could potentially allow clinicians to optimize biomarker use.     

Urinary Biomarkers and Progression of AKI in Patients with Cirrhosis

Background and objectives

AKI is a common and severe complication in patients with cirrhosis. AKI progression was previously shown to correlate with in-hospital mortality. Therefore, accurately predicting which patients are at highest risk for AKI progression may allow more rapid and targeted treatment. Urinary biomarkers of structural kidney injury associate with AKI progression and mortality in multiple settings of AKI but their prognostic performance in patients with liver cirrhosis is not well known.

Design, setting, participants, & measurements

A multicenter, prospective cohort study was conducted at four tertiary care United States medical centers between 2009 and 2011. The study comprised patients with cirrhosis and AKI defined by the AKI Network criteria evaluating structural (neutrophil gelatinase–associated lipocalin, IL-18, kidney injury molecule-1 [KIM-1], liver-type fatty acid–binding protein [L-FABP], and albuminuria) and functional (fractional excretion of sodium [FENa]) urinary biomarkers as predictors of AKI progression and in-hospital mortality.

Results

Of 188 patients in the study, 44 (23%) experienced AKI progression alone and 39 (21%) suffered both progression and death during their hospitalization. Neutrophil gelatinase–associated lipocalin, IL-18, KIM-1, L-FABP, and albuminuria were significantly higher in patients with AKI progression and death. These biomarkers were independently associated with this outcome after adjusting for key clinical variables including model of end stage liver disease score, IL-18 (relative risk [RR], 4.09; 95% confidence interval [95% CI], 1.56 to 10.70), KIM-1 (RR, 3.13; 95% CI, 1.20 to 8.17), L-FABP (RR, 3.43; 95% CI, 1.54 to 7.64), and albuminuria (RR, 2.07; 95% CI, 1.05–4.10) per log change. No biomarkers were independently associated with progression without mortality. FENa demonstrated no association with worsening of AKI. When added to a robust clinical model, only IL-18 independently improved risk stratification on a net reclassification index.

Conclusions

Multiple structural biomarkers of kidney injury, but not FENa, are independently associated with progression of AKI and mortality in patients with cirrhosis. Injury marker levels were similar between those without progression and those with progression alone.     

Assessment of KDIGO Definitions in Patients with Histopathologic Evidence of Acute Renal Disease

Background and objectives

AKI is a clinical syndrome with various causes involving glomerular, interstitial, tubular, and vascular compartments of the kidney. Acute kidney disease (AKD) is a new concept that includes both AKI and the conditions associated with subacute decreases in GFR (AKD/non-AKI). This study aimed to investigate the correlation between AKI/AKD defined by clinical presentation and diffuse histologic criteria for acute abnormalities based on renal biopsy.

Design, setting, participants, & measurements

All 303 patients who were histologically diagnosed as having acute tubular necrosis (ATN), acute tubulointerstitial nephritis, cellular crescentic GN, acute thrombotic microangiopathy, or complex lesions on renal biopsy from January 2009 to December 2011 were enrolled in the study. The 2012 Kidney Disease Improving Global Outcomes AKD/AKI definitions were applied to classify patients as follows: AKI, AKD/non-AKI, non-AKD, or unclassified.

Results

A total of 273 patients (90.1%) met the AKD criteria; 198 patients (65.3%) were classified as having AKI according to serum creatinine (SCr) and urine output criteria. The urine output criteria added 4.3% to the SCr criteria and reclassified 6.7% of the AKI cases into higher stages. Of patients with ATN on pathology, 79.2% met AKI criteria; this was a higher percentage than for those who had other individual pathologic lesions (50%–64%). The major cause of not being defined as having AKI was a slower SCr increase than that required by the definition of AKI (98, 93.3%). Patients with AKI had more severe clinical conditions and worse short-term renal outcome than those in the non-AKI group.

Conclusions

Diffuse, acute abnormality defined by renal biopsy and AKI defined by clinical presentation are two different entities. Most patients who have diffuse acute histologic findings met the criteria for AKD, whereas only two thirds met the definition of AKI.