title: Does routine repeat testing of critical values offer any advantage over single testing?
abstract: BACKGROUND
  Before being communicated to the caregiver, critical laboratory values are verified by repeat testing to ensure their accuracy and to avoid reporting false or erroneous results.
  
  
  OBJECTIVE
  To determine whether 2 testing runs offered any advantage over a single testing run in ensuring accuracy or in avoiding the reporting of false or erroneous results.
  
  
  METHODS
  Within the hematology laboratory, 5 tests were selected: hemoglobin level, white blood cell count, platelet count, prothrombin time, and activated partial thromboplastin time. A minimum of 500 consecutive critical laboratory test values were collected retrospectively for each test category. The absolute value and the percentage of change between the 2 testing runs for each critical value were calculated and averaged for each test category and then compared with our laboratory's preset, acceptable tolerance limits for reruns.
  
  
  RESULTS
  The mean results obtained for the absolute value and the percentage of change between the testing runs were 0.08 g/dL (1.4%) for hemoglobin levels, 50 cells/µL (10.2%) for white blood cell counts, 1500 cells/µL (9.9%) for platelet counts, 0.7 seconds (1.4%) for prothrombin time, and 5.1 seconds (4.4%) for activated partial thromboplastin time (all within our laboratory's acceptable tolerance limits for reruns). The percentage of specimens with an absolute value or a mean percentage of change outside our laboratory's acceptable tolerance limits for reruns ranged between 0% and 2.2% among the test categories. No false or erroneous results were identified between the 2 testing runs in any category.
  
  
  CONCLUSIONS
  Routine, repeat testing of critical hemoglobin level, platelet count, white blood cell count, prothrombin time, and activated partial thromboplastin time results did not offer any advantage over a single run.
authors.affiliation: Department of Pathology, Anatomy, and Cell Biology, Thomas Jefferson University Hospital, Philadelphia,Pennsylvania 19107, USA. Adam.Toll@JeffersonHospital.org
authors.forename: Adam D
authors.initials: AD
authors.lastname: Toll
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Liu
authors.forename: Gene
authors.initials: G
authors.lastname: Gulati
authors.forename: Eric M
authors.initials: EM
authors.lastname: Behling
authors.forename: William D
authors.initials: WD
authors.lastname: Kocher
mesh_terms: D019963:Clinical Chemistry Tests / Q000706:statistics & numerical data; D003951:Diagnostic Errors / Q000517:prevention & control*; D006403:Hematologic Tests / Q000706:statistics & numerical data; D006801:Humans; D010338:Pathology, Clinical / Q000592:standards*; D012016:Reference Values; D015203:Reproducibility of Results