title: In vitro sensitivity of different activated partial thromboplastin time reagents to mild clotting factor deficiencies.
abstract: BACKGROUND
  Activated partial thromboplastin time (aPTT) is a routine clotting assay that is widely used to globally screen for coagulation abnormalities. It is commonly admitted that a prolonged test result, may trigger the need for specific assays to be performed, particularly factor measurement. However, the sensitivity of aPTT reagents to deficiencies of clotting factors varies.
  
  
  METHODS
  We evaluated, according to the recommendation of the CLSI H47-A2 guideline, the responsiveness to single factor levels of five aPTT reagents by using factor-deficient plasmas spiked with a calibration plasma to produce individual factor activities ranging from <1 to ~100 Unit (U)/dL. Test results were expressed as the sample-to-control ratio, the latter was defined as the clotting time obtained in the calibration plasma containing ~100 U/dL factor activity. The factor activity producing a prolongation of aPTT above the upper limit of its specific normal range (in ratio) was assigned as the factor responsiveness in U/dL to that reagent.
  
  
  RESULTS
  Responsiveness ranged from 34 to 47 U/dL to
  C, from 18 to 57 U/dL to FIX, from 38 to 52 U/dL to FXI, from 29 to 50 U/dL to FXII, from 40 and 59 U/dL to FV, from 7.5 to 49 U/dL to FX, and from 9.1 to 10.5 U/dL to FII.
  
  
  CONCLUSIONS
  These results suggest that the sensitivity of the tested aPTT reagents to single factor deficiency is highly variable. Moreover, for one given aPTT reagent, its sensitivity was very different depending on the deficient factor. This must be considered when analyzing clinical materials.
authors.affiliation: Faculté de Médecine, Laboratoire d'Hématologie, Université Nice Sophia-Antipolis, Nice, France.|CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: P
authors.initials: P
authors.lastname: Toulon
authors.affiliation: CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Eloit
authors.affiliation: Laboratoire d'Hématologie, Hôpital Simone Veil, Eaubonne-Montmorency, France.
authors.forename: M
authors.initials: M
authors.lastname: Smahi
authors.affiliation: CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: C
authors.initials: C
authors.lastname: Sigaud
authors.affiliation: CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: D
authors.initials: D
authors.lastname: Jambou
authors.affiliation: CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: F
authors.initials: F
authors.lastname: Fischer
authors.affiliation: CHU, Hôpital Pasteur, Service d'Hématologie Biologique, Nice, France.
authors.forename: A
authors.initials: A
authors.lastname: Appert-Flory
mesh_terms: D001779:Blood Coagulation Factors / Q000494:pharmacology*; D001780:Blood Coagulation Tests / Q000592:standards; D002138:Calibration; D020147:Coagulation Protein Disorders / Q000175:diagnosis*; D006801:Humans; D007202:Indicators and Reagents; D010314:Partial Thromboplastin Time / Q000592:standards*; D012680:Sensitivity and Specificity
chemical_list: D001779:Blood Coagulation Factors; D007202:Indicators and Reagents
keywords: Factor deficiency; activated partial thromboplastin time; reagents; responsiveness; sensitivity