title: A fit-for-purpose approach to analytical sensitivity applied to a cardiac troponin assay: time to escape the 'highly-sensitive' trap.
abstract: BACKGROUND
  Highly-sensitive cardiac troponin (cTn) assays are being introduced into the market. In this study we argue that the classification of cTn assays into sensitive and highly-sensitive is flawed and recommend a more appropriate way to characterize analytical sensitivity of cTn assays.
  
  
  METHODS
  The raw data of 2252 cardiac troponin I (cTnI) tests done in duplicate with a 'sensitive' assay was extracted and used to calculate the cTnI levels in all, including those below the 'limit of detection' (LoD) that were censored. Duplicate results were used to determine analytical imprecision.
  
  
  RESULTS
  We show that cTnI can be quantified in all samples including those with levels below the LoD and that the actual margins of error decrease as concentrations approach zero.
  
  
  CONCLUSIONS
  The dichotomous classification of cTn assays into sensitive and highly-sensitive is theoretically flawed and characterizing analytical sensitivity as a continuous variable based on imprecision at 0 and the 99th percentile cut-off would be more appropriate.
authors.forename: Jacobus P J
authors.initials: JP
authors.lastname: Ungerer
authors.forename: Carel J
authors.initials: CJ
authors.lastname: Pretorius
mesh_terms: D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000378:metabolism*; D006801:Humans; D012680:Sensitivity and Specificity; D019210:Troponin I / Q000032:analysis*
chemical_list: D019210:Troponin I