title: Biological variation of high sensitivity cardiac troponin-T in stable dialysis patients: implications for clinical practice.
abstract: BACKGROUND
  Changes in high sensitivity cardiac troponin-T (hs-cTnT) concentrations may reflect either acute myocardial injury or biological variation. Distinguishing between these entities is essential to accurate diagnosis, however, the biological variation of hs-cTnT in dialysis population is currently unknown. We sought to estimate the within- and between-person coefficients of variation of hs-cTnT in stable dialysis patients, and derive the critical difference between measurements needed to exclude biological variation with 99% confidence.
  
  
  METHODS
  Fifty-five prevalent haemo- and peritoneal-dialysis patients attending two metropolitan hospitals were assessed on 10 consecutive occasions; weekly for 5 weeks then monthly for 4 months. Assessments were conducted at the same dialysis cycle time-point and entailed hs-cTnT testing, clinical review, electrocardiography, and bioimpedance spectroscopy. Patients were excluded if they developed clinical or physiological instability.
  
  
  RESULTS
  In total 137 weekly and 114 monthly hs-cTnT measurements from 42 stable patients were analysed. Respective between- and within-person coefficients of variation were 83% and 7.9% for weekly measurements, and 79% and 12.6% for monthly measurements. Within-person variation was unaffected by dialysis modality or cardiac co-morbidity. The bidirectional 99% reference change value was -25% and +33% for weekly measurements, and -37% and +58% for monthly measurements.
  
  
  CONCLUSIONS
  The between-person variation of hs-cTnT in the dialysis population is markedly greater than within-person variation indicating that hs-cTnT testing is best applied in this population using a relative change strategy. An increase of 33% or a reduction of 25% in serial hs-cTnT concentrations measured at weekly intervals excludes change due to analytical and biological variation alone with 99% confidence.
authors.forename: Magid A
authors.initials: MA
authors.lastname: Fahim
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Hayen
authors.forename: Andrea R
authors.initials: AR
authors.lastname: Horvath
authors.forename: Goce
authors.initials: G
authors.lastname: Dimeski
authors.forename: Amanda
authors.initials: A
authors.lastname: Coburn
authors.forename: Ken-Soon
authors.initials: KS
authors.lastname: Tan
authors.forename: David W
authors.initials: DW
authors.lastname: Johnson
authors.forename: Jonathan C
authors.initials: JC
authors.lastname: Craig
authors.forename: Scott B
authors.initials: SB
authors.lastname: Campbell
authors.forename: Carmel M
authors.initials: CM
authors.lastname: Hawley
mesh_terms: D000208:Acute Disease; D000368:Aged; D042241:Early Diagnosis; D005260:Female; D006801:Humans; D007677:Kidney Function Tests; D008297:Male; D008875:Middle Aged; D009203:Myocardial Infarction / Q000175:diagnosis* / Q000378:metabolism* / Q000503:physiopathology; D010530:Peritoneal Dialysis; D012680:Sensitivity and Specificity; D020107:Troponin T / Q000378:metabolism*
chemical_list: D020107:Troponin T