Robert H Christenson

American Association for Clinical Chemistry (AACC), Washington, Washington, D.C., United States

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Publications (176)889.07 Total impact

  • Paul O Collinson, Lisa Garrison, Robert H Christenson
    Clinical biochemistry. 11/2014;
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    ABSTRACT: High-sensitivity troponin T (hsTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) strongly predict heart failure (HF) in the general population. However, the interpretation of levels of these biomarkers as predictors of HF is uncertain among patients with CKD. Here, we investigated whether hsTnT and NT-proBNP are associated with incident HF among patients with CKD. In a prospective cohort analysis, we studied 3483 people with CKD in the Chronic Renal Insufficiency Cohort (CRIC) Study recruited from June of 2003 to August of 2008 who were free of HF at baseline. We used Cox regression to examine the association of baseline levels of hsTnT and NT-proBNP with incident HF after adjustment for demographic factors, traditional cardiovascular risk factors, markers of kidney disease, pertinent medication use, and mineral metabolism markers. At baseline, hsTnT levels ranged from ≤5.0 to 378.7 pg/ml, and NT-proBNP levels ranged from ≤5 to 35,000 pg/ml. Compared with those who had undetectable hsTnT, participants in the highest quartile (>26.5 ng/ml) had a significantly higher rate of HF (hazard ratio, 4.77; 95% confidence interval, 2.49 to 9.14). Similarly, compared with those in the lowest NT-proBNP quintile (<47.6 ng/ml), participants in the highest quintile (>433.0 ng/ml) experienced a substantially higher rate of HF (hazard ratio, 9.57; 95% confidence interval, 4.40 to 20.83). In conclusion, hsTnT and NT-proBNP were strongly associated with incident HF among a diverse cohort of individuals with mild to severe CKD. Elevations in these biomarkers may indicate subclinical changes in volume and myocardial stress that subsequently contribute to clinical HF.
    Journal of the American Society of Nephrology : JASN. 10/2014;
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    ABSTRACT: Background Peak creatine kinase (CK)-MB concentration is related to reperfusion success and clinical outcomes after fibrinolytic therapy for acute myocardial infarction. However, prognostic implications of CK-MB measurements after primary percutaneous coronary intervention (PCI), which provides more predictable and consistent reperfusion, are unknown. Methods We pooled 2042 primary PCI-treated ST-segment elevation myocardial infarction (STEMI) patients from 3 trials with serial core laboratory-determined CK-MB measurements; 1799 patients (88.1%) who survived to 36 hours and had ≥4 CK-MB measurements were studied. Cox regression modeling was performed to quantify the association between peak CK-MB concentration (and area under the time-concentration curve [AUC]) and mortality at 6 months, and death or congestive heart failure (CHF) at 90 days. Results The median (25th–75th percentiles) peak CK-MB concentration and AUC measurement through 36 hours were 239 (109–429) ng/mL and 4263 (2081–7124) ng/mL · h, respectively. By multivariable analysis, peak CK-MB concentration and AUC measurement were independently associated with 6-month mortality (adjusted HR 1.15, 95% CI 1.05–1.25, per 100 ng/mL increase, p = 0.002; and adjusted HR 1.09, 95% CI 1.03–1.14, per 1000 ng/mL · h increase, p < 0.001, respectively) and 90-day death or CHF (adjusted HR 1.26, 95% CI 1.18–1.34, p < 0.001; and adjusted HR 1.15, 95% CI 1.11–1.19, p < 0.001, respectively). Conclusions Peak CK-MB concentration and AUC measurement are independent predictors of 3- to 6-month cardiovascular outcomes in primary PCI-treated STEMI patients. Our findings guide application of these measurements as efficacy endpoints in early-phase studies evaluating new therapies for STEMI.
    American Heart Journal 10/2014; · 4.50 Impact Factor
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    ABSTRACT: We investigated absolute and relative cardiac troponin I (TnI) delta changes, optimal sampling protocols, and decision thresholds for early diagnosis of myocardial infarction (MI). Serial cardiac biomarker values demonstrating a rise and/or fall define MI diagnosis; however the magnitude of change, timing, and diagnostic accuracy of absolute versus relative (percentage) deltas remains unsettled.
    Clinical biochemistry. 09/2014;
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    ABSTRACT: To compare emergency department TnI serial sampling intervals, determine optimal diagnostic thresholds, and report representative diagnostic performance characteristics for early rule-in and rule-out of MI.
    Clinical biochemistry. 09/2014;
  • Journal of cardiac failure. 08/2014; 20(8S):S78.
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    ABSTRACT: Background: Renal hemodynamic measurements are complicated to perform in patients with cirrhosis, yet they provide the best measure of risk to predict hepatorenal syndrome (HRS). Currently, there are no established biomarkers of altered renal hemodynamics in cirrhosis validated by measured renal hemodynamics. Methods: In this pilot study, simultaneous measurements of glomerular filtration rate (GFR), renal plasma flow (RPF), renal resistive indices and biomarkers were performed to evaluate renal hemodynamic alterations in 10 patients with cirrhosis (3 patients without ascites, 5 with diuretic-sensitive and 2 diuretic-refractory ascites). Results: Patients with diuretic-refractory ascites had the lowest mean GFR (36.5 ml/min/1.73 m(2)) and RPF (133.6 ml/min/1.73 m(2)) when compared to those without ascites (GFR 82.9 ml/min/1.73 m(2), RPF 229.9 ml/min/1.73 m(2)) and with diuretic-sensitive ascites (GFR 82.3 ml/min/1.73 m(2), RPF 344.1 ml/min/1.73 m(2)). A higher mean filtration fraction (FF) (GFR/RPF 0.36) was noted among those without ascites compared to those with ascites. Higher FF in patients without ascites is most likely secondary to the vasoconstriction in the efferent glomerular arterioles (normal FF ∼0.20). In general, renal resistive indices were inversely related to FF. While patients with ascites had lower FF and higher right kidney main and arcuate artery resistive indices, those without ascites had higher FF and lower right kidney main and arcuate artery resistive indices. While cystatin C and β2-microglobulin performed better compared to Cr in estimating RPF, β-trace protein, β2-microglobulin, and SDMA, and (SDMA+ADMA) performed better in estimating right kidney arcuate artery resistive index. Conclusion: The results of this pilot study showed that identification of non-invasive biomarkers of reduced RPF and increased renal resistive indices can identify cirrhotics at risk for HRS at a stage more amenable to therapeutic intervention and reduce mortality from kidney failure in cirrhosis. © 2014 S. Karger AG, Basel.
    American journal of nephrology. 06/2014; 39(6):543-552.
  • Robert H Christenson, Cheryl A Kassed
    Journal of comparative effectiveness research. 05/2014; 3(3):221-4.
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    ABSTRACT: There is uncertainty regarding treatment of hypertension in hemodialysis patients due to the observed J-shaped association between blood pressure (BP) and death. We hypothesized that this association reflects confounding by cardiovascular disease (CVD) and that stratification by CVD biomarkers, cardiac troponin I (cTnI) and N-terminal fragment of prohormone brain natriuretic peptide (NT-proBNP), might change this association. National prospective cohort study. 446 incident hemodialysis patients. Predialysis systolic BP. Mortality (all-cause and CVD) and first CVD event assessed using Cox regression adjusted for demographics, comorbid conditions, and clinical factors. Participants with cTnI level≥0.1ng/mL or NT-proBNP level≥9,252pg/mL were classified as the high-biomarker group; remaining participants were included in the low-biomarker group. Participants in the high-biomarker group (n=138 [31%]) were older (61 vs 57 years) and had a higher prevalence of CVD (67% vs 23%), but similar baseline BPs (152 vs 153mmHg). There were 323 deaths (143 from CVD) and 271 CVD events. The high-biomarker group had a higher risk of mortality than the low-biomarker group (HR, 1.75; 95%CI, 1.37-2.24). The association between BP and outcomes differed between the 2 biomarker groups (P for interaction=0.01, 0.2, and 0.07 for all-cause mortality, CVD mortality, and first CVD event, respectively). In the low-biomarker group, BP was associated with greater risk of outcomes: HR per 10mmHg higher BP was 1.07 (95%CI, 1.01-1.14), 1.10 (95%CI, 0.96-1.25), and 1.04 (95%CI, 0.96-1.13) for all-cause mortality, CVD mortality, and first CVD event, respectively. Importantly, lower BP was not associated with increased risk of outcomes in stratified models, including for those in high biomarker group. BP measurements not standardized. The observed J-shaped association between BP and outcomes in hemodialysis patients is due to confounding by subclinical CVD. A stratification approach based on cTnI and NT-proBNP levels has the potential to inform BP treatment in hemodialysis patients.
    American Journal of Kidney Diseases 04/2014; · 5.29 Impact Factor
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    ABSTRACT: Reference intervals of high-sensitivity troponin T (hs-cTnT) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) have been determined from Western populations. No data are available regarding expected values in Asian populations.METHODS: A total of 1157 age- and sex-matched healthy individuals (mean age, 41.2 years; 48.0% male) were prospectively enrolled from the US (n = 565) and Vietnam (n = 592). Blood samples were analyzed for hs-cTnT and NT-proBNP. Median values were determined for each country and compared in unadjusted analyses and in analyses adjusted for age, sex, body mass index, study site, race, and vital signs.RESULTS: Median hs-cTnT concentrations were slightly higher for individuals from the US than for those from Vietnam, but both were below the limit of detection (3.7 vs 3.0 ng/L, respectively; P = 0.03). More US participants had an hs-cTnT concentration above the limit of detection (57.2% vs 47.3%; P = 0.001), but the 99th percentile concentration was slightly higher for Asians (US 15.1 vs Vietnam 19.0 ng/L). Concentrations for >98% of both populations were below the standard hs-cTnT 99th percentile of 14.0 ng/L (P = 0.54). Median NT-proBNP concentrations were slightly higher for US participants compared with Vietnamese participants (28 vs 16 ng/L, respectively; P < 0.001). Following adjustment, differences in concentrations of NT-proBNP between healthy US and Vietnamese populations remained significant, whereas for hs-cTnT the differences were no longer significant. Inclusion of hs-cTnT values down to the limit of blank did not change the result.CONCLUSIONS: The differences in hs-cTnT and NT-proBNP between healthy individuals from the US and Vietnam are small. Previously derived reference intervals for both analytes may be applied in Asian populations.
    Clinical Chemistry 02/2014; · 7.15 Impact Factor
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    ABSTRACT: Heart failure (HF) is a prevalent disease that is associated with a high morbidity and mortality; HF is estimated to cost the US healthcare system over US$39 billion annually. Biomarkers have an increasingly important role in achieving management goals through rapid diagnosis and monitoring of disease processes. HF is a target for healthcare cost control measures and quality improvement metrics. In achieving these benchmarks, point-of-care testing, the development of more sensitive assays for traditional biomarkers and determining appropriate applications for novel markers will be essential in meeting these health quality and cost-driven metrics. Point-of-care applications involving biomarkers can be utilized in inpatient, outpatient and emergency department settings to aid in the rapid diagnosis, risk stratification and management of patients presenting with symptoms consistent with HF. In this paper we review current and promising HF biomarkers with an emphasis on point-of-care testing and its implications in the changing healthcare landscape.
    Expert Review of Molecular Diagnostics 02/2014; · 4.09 Impact Factor
  • Nia W Roberts, Robert H Christenson, Christopher P Price
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    ABSTRACT: Laboratory medicine is strong in the basic scientific background that underpins the pathological rationale for considering the use of a test, as well as characterising analytical performance of laboratory procedures. Evidence of the impact of test utilisation on health outcomes and adding value to the patient's care pathway is more limited. However, purchasers and commissioners of laboratory services, as well as clinicians, are bombarded with a burgeoning literature on new biomarkers and devices, against a backdrop of fiscal constraints. This increasingly critical appraisal of both current practice, as well as new developments, demands that all health professionals are up-to-date in the knowledge of their subject, as well as being able to access and impart this knowledge in real time to their colleagues in the clinical team. This requirement for knowledge means that the laboratory medicine professional can be asked to provide information at any time, from a host of differing scenarios, and with a considerable variation in the depth of response being required. Thus, the biochemist may need to respond to a query from the Emergency Department on the one hand, to preparing the justification for a new test - or disinvestment in an old (and now inappropriate) test, to writing the case for a research grant proposal. All of these scenarios require clarity in the question being asked, and the ability to search for the evidence across a wide range of resources. This review takes the reader through the steps to efficient retrieval of good quality information.
    Annals of Clinical Biochemistry 01/2014; · 1.92 Impact Factor
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    ABSTRACT: Background: Heart failure is a syndrome characterized by the inability of the heart to meet the body's circulatory demands. Heart failure is a growing health issue worldwide and the prevalence of heart failure is expected to rise as populations age. Therapies and interventions for a variety of cardiac conditions continue to advance and biomarkers will play an increasing role in patient management. Methods: This is a review of the clinical research in blood based biomarkers for diagnosis, prognosis and therapeutic guidance of heart failure. The focus of this review is biomarkers that are currently available for clinical measurement, and their current and potential for applications for managing heart failure patients. Results: The various biologic pathways and physiologic processes of heart failure biomarkers represent a host of different including inflammation, remodeling, strain, neurohormonal activation, metabolism and cardiac myocyte injury. The clinical characteristics and applications of each heart failure biomarker are discussed. Conclusion: As populations age and effective treatments and interventions for coronary artery disease improve, heart failure will increase in incidence and prevalence. Blood biomarkers will play an increasing role in the early diagnosis, therapeutic monitoring and management of heart failure patients in the future.
    Clinical biochemistry 01/2014; · 2.02 Impact Factor
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    ABSTRACT: Objectives To determine the 99th percentile upper reference limit for the highly sensitive cardiac troponin T assay (hs-cTnT) in three large independent cohorts. Background The presently recommended 14 ng/L cutpoint for the diagnosis of myocardial infarction using the hs-cTnT assay was derived from small studies of presumably healthy individuals, with relatively little phenotypic characterization. Methods Data were included from three well characterized population-based studies: the Dallas Heart Study (DHS), the Atherosclerosis Risk in Communities (ARIC) Study, and the Cardiovascular Health Study (CHS). Within each cohort, reference subcohorts were defined excluding individuals with recent hospitalization, overt cardiovascular disease and kidney disease (subcohort 1) and further excluding those with subclinical structural heart disease (subcohort 2). Data were analyzed stratified by age, sex and race. Results The 99th percentile values for the hs-cTnT assay in DHS, ARIC and CHS were 18, 22 and 36 ng/L respectively (subcohort 1) and 14, 21 and 28 ng/L respectively (subcohort 2). These differences in 99th percentile values paralleled age differences across cohorts. Analyses within sex/age strata yielded similar results between cohorts. Within each cohort, 99th percentile values increased with age and were higher in men. More than 10% of men aged 65-74 with no cardiovascular disease in our study had cTnT values above the current myocardial infarction threshold. Conclusions Use of a uniform 14 ng/L cutoff for the hs-cTnT assay may lead to over-diagnosis of myocardial infarction, particularly in men and the elderly. Clinical validation is needed of new age- and sex-specific cutoff values for this assay.
    Journal of the American College of Cardiology 01/2014; · 14.09 Impact Factor
  • Eric Christenson, Robert H Christenson
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    ABSTRACT: Cardiac troponin I (cTnI) and T (cTnT) have displaced myoglobin and creatine kinase-MB as the preferred markers of myocardial injury and have become the cornerstones for diagnosis of myocardial infarction (MI). Current guidelines for MI diagnosis give specific recommendations for cTnI and cTnT assays including instructions to reliably measure values in the range of the 99th percentile of a normal reference cohort with good precision, for example, 10% total coefficient of variation. Unfortunately, the nomenclature system that has evolved for cTnI and cTnT is haphazard and unsystematic. It is key to recognize that not all cTnI and cTnT measurement methods are equivalent; hence, knowledge of local measurements is essential for effective evaluation of patients presenting with suspected non-ST elevation MI. For cTnI, the amino acid sequences frequently targeted for effective measurement include residues 41-49 and 83-93 because these regions of the molecule are stable, helping make the assays reproducible. Use of the recommended cutoff at the 99th percentile of a normal cohort is related to improved patient outcomes. Therefore, use of a troponin assay with good measurement characteristics at the 99th percentile, often referred to as 'sensitive assays', is important for patient outcomes. cTnI and cTnT assays with higher sensitivity are becoming available, and their utilization for measurement in asymptomatic populations may be useful for risk assessment and management in the future. However there is currently no evidence that these high-sensitivity assays confer an advantage in the context of MI diagnosis. Currently cTnI assays are not standardized; thus, there can be a substantial difference in values depending on the assay used. An international effort toward standardization is ongoing, but is not anticipated to be completed and implemented for a few years. Our purpose here is to add insight to important characteristics of troponin measurement techniques and how these features may impact clinical utilization of these tests.
    Coronary artery disease 12/2013; 24(8):698-704. · 1.56 Impact Factor
  • Clinica chimica acta; international journal of clinical chemistry 11/2013; · 2.54 Impact Factor
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    Eric Christenson, Robert H Christenson
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    ABSTRACT: Myocardial infarction (MI) is the leading cause of death in the developed world. Biomarkers have an essential role in diagnosis, risk stratification, guiding management and clinical decision making in the setting of patients presenting with signs and symptoms of MI. Cardiac troponin (cTn) rose to prominence during the 1990s and has evolved to be the cornerstone for diagnosis of MI. The current criteria for MI diagnosis include a rise and/or fall in cTn with at least one value above the 99th percentile of the upper reference limit. Along with cTn, the natriuretic peptides B-type natriuretic peptide (BNP) and amino-terminal proBNP (NT-proBNP) have an important role in determining prognosis and guiding management. As assays for cTn have been evolved that are capable of reliably detecting smaller and smaller quantities in the blood, a dilemma has emerged as to how to use this new information. Several studies have attempted to answer this question and have shown that these lower concentrations of cTn have important prognostic significance and, more importantly, that intervention in these patients leads to improved clinical outcomes. New algorithms incorporating BNP, NT-proBNP, and more sensitive cTn assays hold promise for more rapid diagnosis or rule-out of MI, allowing for appropriate management steps to be initiated and more efficient and effective utilization of healthcare resources.
    Annals of Laboratory Medicine 09/2013; 33(5):309-318. · 1.48 Impact Factor
  • Christopher P Price, Robert H Christenson
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    ABSTRACT: The purpose of laboratory medicine is to facilitate better decision making in clinical practice and healthcare delivery. Decision making implies an unresolved issue, problem or unmet need. The most important criterion for any investigation to be of value in clinical practice is that it addresses an unmet need. The different ways in which laboratory investigations are utilized in patient care can be represented in the form of questions. It is important that these questions are articulated to highlight the variables that will impact on the effectiveness of the investigation in the scenario being considered. These variables include the characteristics of the patient (or population) and clinical setting, the nature of the decision and action taken on receipt of the test result and the expected outcome. Asking a question is the first step of the evidence-based laboratory medicine (EBLM) cycle, the other steps being acquiring the evidence, critically appraising the evidence, applying the evidence and auditing use of the evidence. Getting the question right determines the quality of the whole process, thus, defines the quality in practice of laboratory medicine. Whilst the main focus of the EBLM cycle is to provide a strong evidence base for use in clinical practice, it is clear that the five steps are equally applicable in commissioning, delivery and audit (performance management) of services. Asking the right question is crucial to improving the quality of evidence, and practice, in laboratory medicine, and should be used in routine laboratory medicine practice and management throughout healthcare.
    Annals of Clinical Biochemistry 06/2013; · 1.92 Impact Factor
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    ABSTRACT: Conventional creatinine-based glomerular filtration rate (GFR) equations are insufficiently accurate for estimating GFR in cirrhosis. The Chronic Kidney Disease Epidemiology Collaboration (CKD-EPI) recently proposed an equation to estimate GFR in subjects without cirrhosis using both serum creatinine and cystatin C levels. Performance of the new CKD-EPI creatinine-cystatin C equation (2012) was superior to previous creatinine- or cystatin C-based GFR equations. To evaluate the performance of the CKD-EPI creatinine-cystatin C equation in subjects with cirrhosis, we compared it to GFR measured by non-radiolabeled iothalamate plasma clearance (mGFR) in 72 subjects with cirrhosis. We compared the "bias", "precision" and "accuracy" of the new CKD-EPI creatinine-cystatin C equation to that of 24-hour urinary creatinine clearance (CrCl), Cockcroft-Gault (CG) and previously reported creatinine- and/or cystatin C-based GFR-estimating equations. Accuracy of CKD-EPI creatinine-cystatin C equation as quantified by root mean squared error of difference scores [differences between mGFR and estimated GFR (eGFR) or between mGFR and CrCl, or between mGFR and CG equation for each subject] (RMSE=23.56) was significantly better than that of CrCl (37.69, P=0.001), CG (RMSE=36.12, P=0.002) and GFR-estimating equations based on cystatin C only. Its accuracy as quantified by percentage of eGFRs that differed by greater than 30% with respect to mGFR was significantly better compared to CrCl (P=0.024), CG (P=0.0001), 4-variable MDRD (P=0.027) and CKD-EPI creatinine 2009 (P=0.012) equations. However, for 23.61% of the subjects, GFR estimated by CKD-EPI creatinine-cystatin C equation differed from the mGFR by more than 30%. CONCLUSIONS: The diagnostic performance of CKD-EPI creatinine-cystatin C equation (2012) in patients with cirrhosis was superior to conventional equations in clinical practice for estimating GFR. However, its diagnostic performance was substantially worse than reported in non-cirrhotic subjects. (HEPATOLOGY 2013.).
    Hepatology 06/2013; · 12.00 Impact Factor
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    ABSTRACT: OBJECTIVES: In the critical care setting, increasing levels of midregional proadrenomedullin (MRproADM), midregional proatrial natriuretic peptide (MRproANP), procalcitonin (PCT), copeptin, and proendothelin-1 (proET-1) have been shown to be correlated with increasing severity of sepsis. The objective of this study was to investigate the utility of sepsis biomarkers in an Emergency Department (ED) population. METHODS: Through a prospective, observational pilot study, we investigated the utility of MRproADM, MRproANP, PCT, copeptin, and proET-1 in predicting a diagnosis of early sepsis in patients presenting to the ED for suspected infection. Data were analyzed using nonparametric Mann-Whitney U-tests, χ-tests, and receiver operating characteristic curves. RESULTS: Of the 66 patients enrolled in this study, 37 (56.1%) were men, with a median age of 58 years [interquartile range (IQR) 39-69 years], and 19 (28.8%) had a final diagnosis of early sepsis. A higher percentage of sepsis patients compared with no-sepsis patients met systemic inflammatory response syndrome (SIRS) criteria at initial presentation (85.7 vs. 41.3%; P<0.0001) and were admitted to the hospital (84.2 vs. 55.6%; P=0.02). PCT was higher in sepsis patients [median 0.32 ng/ml (IQR 0.19-1.17) vs. 0.18 ng/ml (IQR 0.07-0.54); P=0.04]. There were no differences between groups for MRproADM, MRproANP, copeptin, or proET-1 (P≥0.53). The C-statistic was maximized with the combination of SIRS criteria and PCT levels (0.92±0.05), which was better than PCT alone (0.67±0.08; P=0.005) or SIRS alone (0.75±0.07; P=0.04). CONCLUSION: In this pilot study, we found that the combination of SIRS criteria and PCT levels is useful for the early detection of sepsis in ED patients with suspected infection. Larger studies investigating use of PCT are necessary.
    European Journal of Emergency Medicine 05/2013; · 0.73 Impact Factor

Publication Stats

5k Citations
889.07 Total Impact Points

Institutions

  • 2014
    • American Association for Clinical Chemistry (AACC)
      Washington, Washington, D.C., United States
  • 1999–2014
    • University of Maryland Medical Center
      • Department of Pathology
      Baltimore, Maryland, United States
  • 1994–2014
    • University of Maryland, Baltimore
      • • Department of Pathology
      • • Division of Cardiology
      • • Department of Medical and Research Technology
      • • Department of Medicine
      Baltimore, Maryland, United States
  • 2013
    • University of Oxford
      • Department of Primary Care Health Sciences
      Oxford, ENG, United Kingdom
    • Johns Hopkins Medicine
      • Department of Medicine
      Baltimore, MD, United States
    • University of California, San Francisco
      • Department of Laboratory Medicine
      San Francisco, CA, United States
  • 2011
    • St George's, University of London
      Londinium, England, United Kingdom
  • 2010–2011
    • Virginia Commonwealth University
      • • Division of Cardiology
      • • School of Medicine
      Richmond, VA, United States
    • University of Otago
      • Department of Public Health (Wellington)
      Dunedin, Otago, New Zealand
  • 2009
    • Mayo Foundation for Medical Education and Research
      Rochester, Michigan, United States
  • 2005–2009
    • The American University in Cairo
      • • Department of Chemistry
      • • School of Sciences and Engineering
      Cairo, Muhafazat al Qahirah, Egypt
  • 2008
    • Oxford University Hospitals NHS Trust
      • Department of Clinical Biochemistry
      Oxford, England, United Kingdom
    • University of Wisconsin–Madison
      Madison, Wisconsin, United States
    • Cleveland Clinic
      Cleveland, Ohio, United States
    • Hospital de la Santa Creu i Sant Pau
      • Biochemistry Services
      Barcelona, Catalonia, Spain
  • 2005–2008
    • Hennepin County Medical Center
      Minneapolis, Minnesota, United States
  • 1991–2008
    • Duke University Medical Center
      • Duke Clinical Research Institute
      Durham, NC, United States
  • 2007
    • American Association for Clinical Chemistry
      American Fork, Utah, United States
    • Washington Hospital Center
      Washington, Washington, D.C., United States
    • Brigham and Women's Hospital
      • Department of Medicine
      Cambridge, MA, United States
  • 2004
    • Duke University
      Durham, North Carolina, United States
    • North Carolina Clinical Research
      Raleigh, North Carolina, United States
    • Hartford Hospital
      • Department of Pathology and Laboratory Medicine
      Hartford, CT, United States
  • 2002
    • LifeBridge Health
      Baltimore, Maryland, United States
    • St. Michael's Hospital
      Toronto, Ontario, Canada
  • 2001
    • University of Hamburg
      • University Heart Center
      Hamburg, Hamburg, Germany