title: Effect of dabigatran on a prothrombinase-based assay for detecting activated protein C resistance: an ex vivo and in vitro study in normal subjects and factor V Leiden carriers.
abstract: BACKGROUND
  The aim of this study was to evaluate ex vivo and in vitro interference of a direct factor IIa inhibitor, dabigatran, on a prothrombinase-based assay to detect activated protein C resistance.
  
  
  METHODS
  An ex vivo study was performed in six heterozygous factor V Leiden carriers and 12 normal subjects without the factor V Leiden mutation who were treated with dabigatran. An in vitro study was also performed considering 12 plasma samples (six from normal subjects and six from heterozygous factor V Leiden carriers) spiked with dabigatran. The dabigatran concentration was evaluated using a diluted thrombin time assay, activated protein C resistance was evaluated using a prothrombinase-based assay.
  
  
  RESULTS
  In both the ex vivo and in vitro studies dabigatran interfered significantly with activated protein C resistance ratios observed in normal subjects and in factor V Leiden heterozygous carriers.
  
  
  CONCLUSIONS
  The results reported in this paper seem to confirm that dabigatran is able to interfere with the Penthafarm prothrombinase-based assay used to study activated protein C resistance, significantly increasing observed ratios. This effect appears to be present already at low concentrations of dabigatran (6 ng/mL) and affects both normal subjects and heterozygous carriers of factor V Leiden. In this group of patients, dabigatran, at concentrations in the therapeutic range (100-200 ng/mL), could markedly increase the activated protein C resistance ratio, bringing it up to within the reference range for normal subjects, thus potentially leading to misclassification of patients.
authors.affiliation: District of Venice Transfusion Department, "Dell'Angelo" Hospital, Venezia Mestre, Venice, Italy.
authors.forename: Gianluca
authors.initials: G
authors.lastname: Gessoni
authors.affiliation: Laboratory Medicine, "Madonna della Navicella" Hospital, Chioggia, Italy.
authors.forename: Sara
authors.initials: S
authors.lastname: Valverde
authors.affiliation: Cardiology and Intensive Care Coronary Unit, "Madonna della Navicella" Hospital, Chioggia, Italy.
authors.forename: Letizia
authors.initials: L
authors.lastname: Valle
authors.affiliation: Dasit SpA, Milan, Italy.
authors.forename: Pierpaolo
authors.initials: P
authors.lastname: Caruso
authors.affiliation: Laboratory Medicine, "Madonna della Navicella" Hospital, Chioggia, Italy.
authors.forename: Francesca
authors.initials: F
authors.lastname: Gessoni
authors.affiliation: Cardiology and Intensive Care Coronary Unit, "Madonna della Navicella" Hospital, Chioggia, Italy.
authors.forename: Roberto
authors.initials: R
authors.lastname: Valle
mesh_terms: D020016:Activated Protein C Resistance / Q000097:blood / Q000175:diagnosis* / Q000235:genetics / Q000378:metabolism; D000991:Antithrombins / Q000494:pharmacology*; D001780:Blood Coagulation Tests / Q000379:methods*; D000069604:Dabigatran / Q000494:pharmacology*; D003951:Diagnostic Errors; D005165:Factor V / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D009154:Mutation; D011486:Protein C / Q000378:metabolism*; D013925:Thromboplastin / Q000378:metabolism*
chemical_list: D000991:Antithrombins; D011486:Protein C; C095381:factor V Leiden; D005165:Factor V; D013925:Thromboplastin; D000069604:Dabigatran