title: Long-term biological variation in cardiac troponin I.
abstract: OBJECTIVE
  To determine the long-term biological variation (BV) of cardiac troponin I.
  
  
  METHODS
  Three samples separated by a mean of 8.7 ± 2.8 months from 17 patients seen in an outpatient clinic. Tropoinin I was measured using a high sensitivity assay from Singulex, Inc.
  
  
  RESULTS
  The long-term analytical, intra-assay and total variation were 15.2%, 27.9%, and 70.9%, respectively. The index of individuality (II) was 0.45, and the reference change value was +98% and -50%, respectively.
  
  
  CONCLUSIONS
  The BV over 9 months was comparable to previously published results over 2 months using the same testing methodology. The II indicates that reference range values are of less value than serial testing.
authors.affiliation: Department of Laboratory Medicine, University of California, San Francisco, CA, USA. wualan@labmed2.ucsf.edu
authors.forename: Alan H B
authors.initials: AH
authors.lastname: Wu
authors.forename: Paul
authors.initials: P
authors.lastname: Akhigbe
authors.forename: Frank
authors.initials: F
authors.lastname: Wians
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015415:Biomarkers / Q000097:blood*; D002318:Cardiovascular Diseases / Q000097:blood* / Q000175:diagnosis; D019963:Clinical Chemistry Tests / Q000379:methods*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012016:Reference Values; D012307:Risk Factors; D013997:Time Factors; D019210:Troponin I / Q000097:blood*
chemical_list: D015415:Biomarkers; D019210:Troponin I