title: Absolute and relative changes (delta) in troponin I for early diagnosis of myocardial infarction: Results of a prospective multicenter trial.
abstract: OBJECTIVE
  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.
  
  
  METHODS
  We prospectively measured TnI (AccuTnI+3™, Beckman Coulter) at serial time intervals in 1929 subjects with chest pain or equivalent symptoms of acute coronary syndrome at 14 medical centers. Diagnosis was adjudicated by an independent central committee.
  
  
  RESULTS
  Elevated TnI above a threshold of 0.03ng/mL demonstrated significant diagnostic efficacy (AUC 0.96). For patients with TnI<0.03ng/mL and symptom onset≥8h, 99.1% (NPV) were diagnosed with conditions other than MI. Absolute delta performed significantly better than relative delta at 1-3h (AUC 0.84 vs 0.69), 3-6h (0.85 vs 0.73), and 6-9h (0.91 vs 0.79). Current recommendations propose ≥20% delta within 3-6h; however, results were optimized using an absolute delta of 0.01 or 0.02ng/mL. Sensitivity results for absolute delta at 1-3h and 3-6h (75.8%, 78.3%) were superior to relative delta (48.0%, 61.3%). NPV (rule out) was 99.6% when baseline TnI<0.03ng/mL and absolute delta TnI<0.01ng/mL.
  
  
  CONCLUSIONS
  Absolute delta performed significantly better than relative delta at all time intervals. Baseline TnI and absolute delta may be used in conjunction to estimate probability of MI. Consensus recommendations are supported for sampling on admission and 3h later, repeated at 6h in patients when clinical suspicion remains high.
authors.affiliation: Dept. of Emergency Medicine, Vanderbilt University Medical Center, Nashville, TN, USA. Electronic address: Alan.b.storrow@vanderbilt.edu.
authors.forename: Alan B
authors.initials: AB
authors.lastname: Storrow
authors.affiliation: Dept. of Emergency Medicine, Henry Ford Health System, Detroit, MI, USA.
authors.forename: Richard M
authors.initials: RM
authors.lastname: Nowak
authors.affiliation: Dept. of Emergency Medicine, University of California Davis, Sacramento, CA, USA.
authors.forename: Deborah B
authors.initials: DB
authors.lastname: Diercks
authors.affiliation: Dept. of Emergency Medicine, State University of New York at Stony Brook, Stony Brook, NY, USA.
authors.forename: Adam J
authors.initials: AJ
authors.lastname: Singer
authors.affiliation: Clinical Chemistry Laboratory, San Francisco General Hospital, University of California, San Francisco, CA, USA.
authors.forename: Alan H B
authors.initials: AH
authors.lastname: Wu
authors.affiliation: Dept. of Emergency Medicine, Advocate Christ Medical Center, Oak Lawn, IL, USA.
authors.forename: Erik
authors.initials: E
authors.lastname: Kulstad
authors.affiliation: Dept. of Emergency Medicine, Maricopa Medical Center, Phoenix, AZ, USA.
authors.forename: Frank
authors.initials: F
authors.lastname: LoVecchio
authors.affiliation: Dept. of Emergency Medicine, Maimonides Medical Center, Brooklyn, NY, USA.
authors.forename: Christian
authors.initials: C
authors.lastname: Fromm
authors.affiliation: Chest Pain Center, Medical University of South Carolina, Charleston, SC, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Headden
authors.affiliation: Dept. of Emergency Medicine, Covenant Medical Center, Saginaw, MI, USA.
authors.forename: Tracie
authors.initials: T
authors.lastname: Potis
authors.affiliation: Dept. of Emergency Medicine, Virginia Commonwealth University Medical Center, Richmond, VA, USA.
authors.forename: Christopher J
authors.initials: CJ
authors.lastname: Hogan
authors.affiliation: Dept. of Emergency Medicine, Case Western Reserve University School of Medicine, MetroHealth Medical Center, Cleveland, OH, USA.
authors.forename: Jon W
authors.initials: JW
authors.lastname: Schrock
authors.affiliation: Dept. of Emergency Medicine, The Ohio State University Medical Center, Columbus, OH, USA.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Zelinski
authors.affiliation: Dept. of Emergency Medicine, Lehigh Valley Health Network, Allentown, PA, USA.
authors.forename: Marna R
authors.initials: MR
authors.lastname: Greenberg
authors.affiliation: Dept. of Pathology, University of Maryland Medical Center, Baltimore, MD, USA.
authors.forename: Robert H
authors.initials: RH
authors.lastname: Christenson
authors.affiliation: Dept. of Pathology and Laboratory Medicine, Emory University, Atlanta, GA, USA.
authors.forename: James C
authors.initials: JC
authors.lastname: Ritchie
authors.affiliation: Dept. of Clinical Research, Beckman Coulter, Inc., Carlsbad, CA, USA.
authors.forename: Janna S
authors.initials: JS
authors.lastname: Chamberlin
authors.affiliation: Dept. of Clinical Research, Beckman Coulter, Inc., Carlsbad, CA, USA.
authors.forename: Kurtis R
authors.initials: KR
authors.lastname: Bray
authors.affiliation: Dept. of Clinical Research, Beckman Coulter, Inc., Carlsbad, CA, USA.
authors.forename: Daniel W
authors.initials: DW
authors.lastname: Rhodes
authors.affiliation: Dept. of Clinical Research, Beckman Coulter, Inc., Carlsbad, CA, USA.
authors.forename: Deirdre
authors.initials: D
authors.lastname: Trainor
authors.affiliation: Dept. of Clinical Research, Beckman Coulter, Inc., Carlsbad, CA, USA.
authors.forename: Paula C
authors.initials: PC
authors.lastname: Southwick
mesh_terms: D015415:Biomarkers / Q000097:blood; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D008297:Male; D009203:Myocardial Infarction / Q000097:blood* / Q000175:diagnosis*; D011446:Prospective Studies; D013997:Time Factors; D019210:Troponin I / Q000097:blood*
chemical_list: D015415:Biomarkers; D019210:Troponin I
keywords: Acute coronary syndrome; Biomarker; Chest pain diagnosis; Myocardial infarction; Troponin