Matthew E. Lissauer

Discovery and validation of cell cycle arrest biomarkers in human acute kidney injury

IntroductionAcute kidney injury (AKI) can evolve quickly and clinical measures of function often fail to detect AKI at a time when interventions are likely to provide benefit. Identifying early markers of kidney damage has been difficult due to the complex nature of human AKI, in which multiple etiologies exist. The objective of this study was to identify and validate novel biomarkers of AKI.MethodsWe performed two multicenter observational studies in critically ill patients at risk for AKI - discovery and validation. The top two markers from discovery were validated in a second study (Sapphire) and compared to a number of previously described biomarkers. In the discovery phase, we enrolled 522 adults in three distinct cohorts including patients with sepsis, shock, major surgery, and trauma and examined over 300 markers. In the Sapphire validation study, we enrolled 744 adult subjects with critical illness and without evidence of AKI at enrollment; the final analysis cohort was a heterogeneous sample of 728 critically ill patients. The primary endpoint was moderate to severe AKI (KDIGO stage 2 to 3) within 12 hours of sample collection.ResultsModerate to severe AKI occurred in 14% of Sapphire subjects. The two top biomarkers from discovery were validated. Urine insulin-like growth factor-binding protein 7 (IGFBP7) and tissue inhibitor of metalloproteinases-2 (TIMP-2), both inducers of G1 cell cycle arrest, a key mechanism implicated in AKI, together demonstrated an AUC of 0.80 (0.76 and 0.79 alone). Urine [TIMP-2]·[IGFBP7] was significantly superior to all previously described markers of AKI (P <0.002), none of which achieved an AUC >0.72. Furthermore, [TIMP-2]·[IGFBP7] significantly improved risk stratification when added to a nine-variable clinical model when analyzed using Cox proportional hazards model, generalized estimating equation, integrated discrimination improvement or net reclassification improvement. Finally, in sensitivity analyses [TIMP-2]·[IGFBP7] remained significant and superior to all other markers regardless of changes in reference creatinine method.ConclusionsTwo novel markers for AKI have been identified and validated in independent multicenter cohorts. Both markers are superior to existing markers, provide additional information over clinical variables and add mechanistic insight into AKI.Trial registrationClinicalTrials.gov number NCT01209169.

Validation of Cell-Cycle Arrest Biomarkers for Acute Kidney Injury Using Clinical Adjudication

RATIONALE We recently reported two novel biomarkers for acute kidney injury (AKI), tissue inhibitor of metalloproteinases (TIMP)-2 and insulin-like growth factor binding protein 7 (IGFBP7), both related to G1 cell cycle arrest. OBJECTIVES We now validate a clinical test for urinary [TIMP-2]·[IGFBP7] at a high-sensitivity cutoff greater than 0.3 for AKI risk stratification in a diverse population of critically ill patients. METHODS We conducted a prospective multicenter study of 420 critically ill patients. The primary analysis was the ability of urinary [TIMP-2]·[IGFBP7] to predict moderate to severe AKI within 12 hours. AKI was adjudicated by a committee of three independent expert nephrologists who were masked to the results of the test. MEASUREMENTS AND MAIN RESULTS Urinary TIMP-2 and IGFBP7 were measured using a clinical immunoassay platform. The primary endpoint was reached in 17% of patients. For a single urinary [TIMP-2]·[IGFBP7] test, sensitivity at the prespecified high-sensitivity cutoff of 0.3 (ng/ml)(2)/1,000 was 92% (95% confidence interval [CI], 85-98%) with a negative likelihood ratio of 0.18 (95% CI, 0.06-0.33). Critically ill patients with urinary [TIMP-2]·[IGFBP7] greater than 0.3 had seven times the risk for AKI (95% CI, 4-22) compared with critically ill patients with a test result below 0.3. In a multivariate model including clinical information, urinary [TIMP-2]·[IGFBP7] remained statistically significant and a strong predictor of AKI (area under the curve, 0.70, 95% CI, 0.63-0.76 for clinical variables alone, vs. area under the curve, 0.86, 95% CI, 0.80-0.90 for clinical variables plus [TIMP-2]·[IGFBP7]). CONCLUSIONS Urinary [TIMP-2]·[IGFBP7] greater than 0.3 (ng/ml)(2)/1,000 identifies patients at risk for imminent AKI. Clinical trial registered with www.clinicaltrials.gov (NCT 01573962).

Gene expression profiles differentiate between sterile SIRS and early sepsis.

Introduction:The systemic inflammatory response syndrome (SIRS) occurs frequently in critically ill patients and presents similar clinical appearances despite diverse infectious and noninfectious etiologies. Despite similar phenotypic expression, these diverse SIRS etiologies may induce divergent genotypic expressions. We hypothesized that gene expression differences are present between sepsis and uninfected SIRS prior to the clinical appearance of sepsis. Methods:Critically ill uninfected SIRS patients were followed longitudinally for the development of sepsis. All patients had whole blood collected daily for gene expression analysis by Affymetrix Hg_U133 2.0 Plus microarrays. SIRS patients developing sepsis were compared with those remaining uninfected for differences in gene expression at study entry and daily for 3 days prior to conversion to sepsis. Acceptance criteria for differentially expressed genes required: >1.2 median fold change between groups and significance on univariate and multivariate analysis. Differentially expressed genes were annotated to pathways using DAVID 2.0/EASE analysis. Results:A total of 12,782 (23.4%) gene probes were differentially expressed on univariate analysis 0 to 48 hours before clinical sepsis. 626 (1.1%) probes met acceptance criteria, corresponding to 459 unique genes, 65 (14.2%) down and 395 (85.8%) up expressed. These genes annotated to 10 pathways that functionally categorized to 4 themes involving innate immunity, cytokine receptors, T cell differentiation, and protein synthesis regulation. Conclusions:Sepsis has a unique gene expression profile that is different from uninfected inflammation and becomes apparent prior to expression of the clinical sepsis phenotype.

TIMP2•IGFBP7 biomarker panel accurately predicts acute kidney injury in high-risk surgical patients

BACKGROUND Acute kidney injury (AKI) is an important complication in surgical patients. Existing biomarkers and clinical prediction models underestimate the risk for developing AKI. We recently reported data from two trials of 728 and 408 critically ill adult patients in whom urinary TIMP2•IGFBP7 (NephroCheck, Astute Medical) was used to identify patients at risk of developing AKI. Here we report a preplanned analysis of surgical patients from both trials to assess whether urinary tissue inhibitor of metalloproteinase 2 (TIMP-2) and insulin-like growth factor–binding protein 7 (IGFBP7) accurately identify surgical patients at risk of developing AKI. STUDY DESIGN We enrolled adult surgical patients at risk for AKI who were admitted to one of 39 intensive care units across Europe and North America. The primary end point was moderate-severe AKI (equivalent to KDIGO [Kidney Disease Improving Global Outcomes] stages 2–3) within 12 hours of enrollment. Biomarker performance was assessed using the area under the receiver operating characteristic curve, integrated discrimination improvement, and category-free net reclassification improvement. RESULTS A total of 375 patients were included in the final analysis of whom 35 (9%) developed moderate-severe AKI within 12 hours. The area under the receiver operating characteristic curve for [TIMP-2]•[IGFBP7] alone was 0.84 (95% confidence interval, 0.76–0.90; p < 0.0001). Biomarker performance was robust in sensitivity analysis across predefined subgroups (urgency and type of surgery). CONCLUSION For postoperative surgical intensive care unit patients, a single urinary TIMP2•IGFBP7 test accurately identified patients at risk for developing AKI within the ensuing 12 hours and its inclusion in clinical risk prediction models significantly enhances their performance. LEVEL OF EVIDENCE Prognostic study, level I.

Differential expression of toll-like receptor genes: sepsis compared with sterile inflammation 1 day before sepsis diagnosis.

Toll-like receptors (TLRs) are critical components of innate immunity. This study was designed to evaluate differential expression of genes for TLR and associated signal transduction molecules in critically ill patients developing sepsis compared with those with sterile inflammation. Uninfected critically ill patients with systemic inflammatory response syndrome were prospectively followed daily for development of sepsis. They were divided into two groups and compared in a case-control manner: (a) preseptic patients (n = 45) who subsequently developed sepsis, and (b) uninfected systemic inflammatory response syndrome patients (n = 45) who remained uninfected. Whole blood RNA was collected (PAXGene tube) at study entry and 1, 2, and 3 days before clinical sepsis diagnosis (or time-matched uninfected control) and analyzed via Affymetrix Hg_U133 Plus 2.0 microarrays. Genes were considered differentially expressed if they met univariate significance controlled for multiple comparisons at P < 0.005. Differentially expressed probes were uploaded into the Database for Annotation, Visualization and Integrated Discovery. The TLR pathway (Kyoto Encyclopedia of Genes and Genomes-KEGG) significance was determined via Expression Analysis Systematic Explorer (EASE) scoring. A total of 2,974 Affymetrix probes representing 2,190 unique genes were differentially expressed 1 day before sepsis diagnosis. Thirty-six probes representing 25 genes were annotated to the TLR pathway (KEGG) via the Database for Annotation, Visualization and Integrated Discovery with an EASE score at P < 0.0004. Notable TLR genes demonstrating increased expression include TLR-4 (median, 1.43-fold change), TLR-5 (2.08-fold change), and MAPK14 (1.90-fold change). An additional 11 unique genes were manually annotated into the TLR pathway based on known relevance such as TLR-8 (1.54-fold change). The total 36 genes contained 28 showing increased expression and 8 showing decreased expression. Differential gene expression was noted for TLR receptors (eight genes), TLR intracellular signal transduction cascade molecules (27 genes), and TLR-related effector molecules (one gene). The TLR and downstream signaling genes are differentially expressed in critically ill patients developing sepsis compared with those with sterile inflammation. These expression differences occur before phenotypic-based diagnosis of clinical sepsis.

Automated Prediction of Early Blood Transfusion and Mortality in Trauma Patients

BACKGROUND Prediction of blood transfusion needs and mortality for trauma patients in near real time is an unrealized goal. We hypothesized that analysis of pulse oximeter signals could predict blood transfusion and mortality as accurately as conventional vital signs (VSs). METHODS Continuous VS data were recorded for direct admission trauma patients with abnormal prehospital shock index (SI = heart rate [HR] / systolic blood pressure) greater than 0.62. Predictions of transfusion during the first 24 hours and in-hospital mortality using logistical regression models were compared with DeLong’s method for areas under receiver operating characteristic curves (AUROCs) to determine the optimal combinations of prehospital SI and HR, continuous photoplethysmographic (PPG), oxygen saturation (SpO2), and HR-related features. RESULTS We enrolled 556 patients; 37 received blood within 24 hours; 7 received more than 4 U of red blood cells in less than 4 hours or “massive transfusion” (MT); and 9 died. The first 15 minutes of VS signals, including prehospital HR plus continuous PPG, and SpO2 HR signal analysis best predicted transfusion at 1 hour to 3 hours, MT, and mortality (AUROC, 0.83; p < 0.03) and no differently (p = 0.32) from a model including blood pressure. Predictions of transfusion based on the first 15 minutes of data were no different using 30 minutes to 60 minutes of data collection. SI plus PPG and SpO2 signal analysis (AUROC, 0.82) predicted 1-hour to 3-hour transfusion, MT, and mortality no differently from pulse oximeter signals alone. CONCLUSION Pulse oximeter features collected in the first 15 minutes of our trauma patient resuscitation cohort, without user input, predicted early MT and mortality in the critical first hours of care better than the currently used VS such as combinations of HR and systolic blood pressure or prehospital SI alone. LEVEL OF EVIDENCE Therapeutic/prognostic study, level II.

Blood alcohol content, injury severity, and adult respiratory distress syndrome

BACKGROUND Elevated blood alcohol content (BAC) is a risk factor for injury. Associations of BAC with adult respiratory distress syndrome (ARDS) have not been conclusively established. We evaluated the association of a BAC greater than 0 mg/dL with the intermediate outcomes, Injury Severity Score (ISS) and Glasgow Coma Scale (GCS) score, and their association with ARDS development. METHODS This is an observational retrospective cohort study of 26,305 primary trauma admissions to a statewide referral trauma center from July 11, 2003, to October 31, 2011. Logistic regression was performed to assess the relationship between admission BAC, ISS, GCS score, and ARDS development within 5 days of admission. RESULTS The case rate for ARDS was 5.5% (1,447). BAC greater than 0 mg/dL was associated with ARDS development in adjusted analysis (odds ratio, 1.50; 95% confidence interval [CI], 1.33–1.71; p < 0.001). High ISS (≥16) had a stronger association with ARDS development (odds ratio, 17.99; 95% CI, 15.51–20.86), as did low GCS score (⩽8) (odds ratio, 8.77; 95% CI, 7.64–10.07; p < 0.001). Patients with low GCS score and high ISS had the most frequent ARDS (33.6%) and the highest case-fatality rate without ARDS (24.7%). CONCLUSION Elevated BAC is associated with ARDS development. In the analysis of alcohol exposure, ISS and GCS score occur after alcohol ingestion, making them intermediate outcomes. ISS and GCS score were strong predictors of ARDS and may be useful to identify at-risk patients. Elevated BAC may increase the frequency of the ARDS through influence on injury severity or independent molecular mechanisms, which can be discriminated only in experimental models. LEVEL OF EVIDENCE Epidemiologic study, level III.

Risk factors for central line-associated bloodstream infections in the era of best practice.

BACKGROUND: Best clinical practice aims to eliminate central line-associated blood stream infections (CLABSIs). However, CLABSIs still occur. This studys aim was to identify risk factors for CLABSI in the era of best practice. METHODS: Critically ill surgical patients admitted over 2 years to the intensive care unit (ICU) for ≥4 days were studied. Patients with CLABSI as cause for ICU admission were excluded. Patients who developed CLABSI (National Healthcare Safety Network definition) were compared with those who did not. Hand hygiene, maximal sterile barriers, chlorhexidine scrub, avoidance of femoral vein, and proper maintenance were emphasized. Variables collected included demographics, diagnosis, and severity of illness using the Acute Physiology and Chronic Health Evaluation (APACHE) IV database and the hospital central data repository. RESULTS: Of 961 patients studied, 51 patients (5.2%) developed 59 CLABSIs. Mean time from ICU admission to CLABSI was 26 days ± 26 days. The CLABSI group was more likely to be male (odds ratio [OR] 1.93, 95% confidence interval [CI] 1.02–3.68), more critically ill on ICU admission (APACHE IV score 85.2 ± 21.9 vs. 65.6 ± 23.2, p < 0.01), more likely admitted to the emergency surgery service (OR 1.92, 95% CI 1.02–3.61), and had an association with reopening of recent laparotomy (OR 2.08, 95% CI 1.10–3.94). CONCLUSION: In the era of best practice, patients who develop CLABSI are clinically distinct from those who do not develop CLABSI. These CLABSIs may be due to deficiencies of the CLABSI definition or represent patient populations requiring enhanced prevention techniques. LEVEL OF EVIDENCE: III, prognostic study.

Epidemiology and outcomes of acute kidney injury in critically ill surgical patients

PURPOSE Acute kidney injury (AKI) is common in critically ill patients but is poorly defined in surgical patients. We studied AKI in a representative cohort of critically ill surgical patients. METHODS This was a retrospective 1-year cohort study of general surgical intensive care unit patients. Patients were identified from a prospective database, and clinical data were reviewed. Acute kidney injury events were defined by risk, injury, failure, loss, and end-stage renal classification criteria. Outcomes were inpatient and 1-year mortality, inpatient lengths of stay, and discharge renal function. Risk factors for AKI and outcomes were compared by univariate and multivariate analyses. RESULTS Of 624 patients, 296 (47%) developed AKI. Forty-two percent of events were present upon admission, whereas 36% occurred postoperatively. Risk, injury, failure, loss, and end-stage renal classification distributions by grade were as follows: risk, 152 (51%); injury, 69 (23%); and failure, 75 (25%). Comorbid diabetes, emergency admission, major surgery, sepsis, and illness severity were independently associated with renal dysfunction. Patients with AKI had significantly worse outcomes, including increased inpatient and 1-year mortality. Acute kidney injury starting before admission was associated with worse renal dysfunction and greater renal morbidity than de novo inpatient events. CONCLUSIONS Acute kidney injury is common in critically ill surgical patients and is associated with increased mortality, persisting renal impairment and greater resource use.

Increased ICU resource needs for an academic emergency general surgery service

Objective:ICU needs of nontrauma emergency general surgery patients are poorly described. This study was designed to compare ICU utilization of emergency general surgery patients admitted to an acute care emergency surgery service with other general surgery patients. Our hypothesis is that tertiary care emergency general surgery patients utilize more ICU resources than other general surgical patients. Design:Retrospective database review. Setting:Academic, tertiary care, nontrauma surgical ICU. Patients:All patients admitted to the surgical ICU over age 18 between March 2004 and June 2012. Interventions:None. Measurements and Main Results:Six thousand ninety-eight patients were evaluated: 1,053 acute care emergency surgery, 1,964 general surgery, 1,491 transplant surgery, 995 facial surgery/otolaryngology, and 595 neurosurgery. Acute care emergency surgery patients had statistically significantly longer ICU lengths of stay than other groups: acute care emergency surgery (13.5 ± 17.4 d) versus general surgery (8.7 ± 12.9), transplant (7.8 ± 11.6), oral-maxillofacial surgery (5.5 ± 4.2), and neurosurgery (4.47 ± 9.8) (all p< 0.01). Ventilator usage, defined by percentage of total ICU days patients required mechanical ventilation, was significantly higher for acute care emergency surgery patients: acute care emergency surgery 73.4% versus general surgery 64.9%, transplant 63.3%, oral-maxillofacial surgery 58.4%, and neurosurgery 53.1% (all p < 0.01). Continuous renal replacement therapy usage, defined as percent of patients requiring this service, was significantly higher in acute care emergency surgery patients: acute care emergency surgery 10.8% versus general surgery 4.3%, transplant 6.6%, oral-maxillofacial surgery 0%, and neurosurgery 0.5% (all p < 0.01). Acute care emergency surgery patients were more likely interhospital transfers for tertiary care services than general surgery or transplant (24.5% vs 15.5% and 8.3% respectively, p < 0.001 for each) and more likely required emergent surgery (13.7% vs 6.7% and 3.5%, all p < 0.001). Chronic comorbidities were similar between acute care emergency surgery and general surgery, whereas transplant had fewer. Conclusions:Emergency general surgery patients have increased ICU needs in terms of length of stay, ventilator usage, and continuous renal replacement therapy usage compared with other services, perhaps due to the higher percentage of transfers and emergent surgery required. These patients represent a distinct population. Understanding their resource needs will allow for better deployment of hospital resources.