title: Weekly and 90-minute biological variations in cardiac troponin T and cardiac troponin I in hemodialysis patients and healthy controls.
abstract: BACKGROUND
  Myocardial infarction (MI) is diagnosed by the finding of a single cardiac troponin value above the 99th percentile and a significant time-dependent change in cardiac troponin concentration. The aim of this study was to determine the 90-min and weekly biological variations, the reference change value (RCV), and the index of individuality (II) of high-sensitivity cardiac troponin T (hs-cTnT) (Roche Diagnostics) and hs-cTnI (Abbott Diagnostics) in patients receiving hemodialysis (HD) and in healthy individuals.
  
  
  METHODS
  Blood samples were collected from 19 HD patients (on an HD-free day) and 20 healthy individuals at 90-min intervals over a 6-h period (between 08:30 and 14:30) and before the midweek HD treatment for 10 weeks. The within-person variation (CVi), between-person variation, RCV, and II were calculated.
  
  
  RESULTS
  During the 6-h sampling period, the concentrations of hs-cTnT (both groups) and hs-cTnI (HD patients only) decreased on average by 0.8% to 1.7% per hour, respectively. These declining trends were included in the calculation of a 90-min asymmetric RCV: -8%/+5% in HD patients (hs-cTnT), -18%/+21% in HD patients (hs-cTnI), -27%/+29% in healthy individuals (hs-cTnT), and -39%/+64% in healthy individuals (hs-cTnI). The II was low in both groups for both assays. The weekly CVi values were approximately 8% (hs-cTnT) and 15% (hs-cTnI) in both groups.
  
  
  CONCLUSIONS
  When using a cardiac troponin change of 20%-50% to diagnose an MI, the false-positive rate is likely to be lower for the hs-cTnT assay than for the hs-cTnI assay. The low II suggests that use of a diagnostic cutoff value can be omitted.
authors.affiliation: Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway; Norwegian Clinical Chemistry EQA Program, Bergen, Norway; kristin.moberg.aakre@helse-bergen.no.
authors.forename: Kristin M
authors.initials: KM
authors.lastname: Aakre
authors.affiliation: Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway;
authors.forename: Thomas
authors.initials: T
authors.lastname: Røraas
authors.affiliation: Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway;
authors.forename: Per Hyltoft
authors.initials: PH
authors.lastname: Petersen
authors.affiliation: Department of Clinical Medicine, University of Bergen, Bergen, Norway; Department of Medicine, Haukeland University Hospital, Bergen, Norway;
authors.forename: Einar
authors.initials: E
authors.lastname: Svarstad
authors.affiliation: Department of Medicine, Haukeland University Hospital, Bergen, Norway;
authors.forename: Hilde
authors.initials: H
authors.lastname: Sellevoll
authors.affiliation: Laboratory of Clinical Biochemistry, Stavanger University Hospital, Stavanger, Norway.
authors.forename: Øyvind
authors.initials: Ø
authors.lastname: Skadberg
authors.affiliation: Department of Medicine, Haukeland University Hospital, Bergen, Norway;
authors.forename: Kristin
authors.initials: K
authors.lastname: Sæle
authors.affiliation: Laboratory of Clinical Biochemistry, Haukeland University Hospital, Bergen, Norway; Norwegian Quality Improvement of Primary Care Laboratories (NOKLUS), Department of Public Health and Primary Health Care, University of Bergen, Bergen, Norway;
authors.forename: Sverre
authors.initials: S
authors.lastname: Sandberg
mesh_terms: D000328:Adult; D000368:Aged; D015415:Biomarkers / Q000097:blood; D005189:False Positive Reactions; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000097:blood* / Q000175:diagnosis*; D012016:Reference Values; D006435:Renal Dialysis; D012680:Sensitivity and Specificity; D013997:Time Factors; D019210:Troponin I / Q000097:blood*; D020107:Troponin T / Q000097:blood*
chemical_list: D015415:Biomarkers; D019210:Troponin I; D020107:Troponin T