title: Coagulation assays and plasma fibrinogen concentrations in real-world patients with atrial fibrillation treated with dabigatran.
abstract: OBJECTIVE
  In patients with atrial fibrillation prescribed dabigatran, the aim was to examine the correlation between plasma dabigatran concentrations and the three screening coagulation assays [international normalized ratio (INR), activated partial thromboplastin time (aPTT) and thrombin time (TT)] as well as the dilute thrombin time (dTT) and to examine the contribution of plasma fibrinogen concentrations to the variability in TT results.
  
  
  METHODS
  Plasma from patients with atrial fibrillation on dabigatran were analysed for clotting times and concentrations of fibrinogen and dabigatran. Correlation plots (and associated r(2) values) were generated using these data. The variability in TT results explained by fibrinogen concentrations was quantified using linear regression.
  
  
  RESULTS
  Fifty-two patients (38-94 years old) contributed 120 samples, with plasma dabigatran concentrations ranging from 9 to 408 μg l(-1) . The r(2) values of INR, aPTT, TT and dTT against plasma dabigatran concentrations were 0.49, 0.54, 0.70 and 0.95, respectively. Plasma fibrinogen concentrations explained some of the residual variability in TT values after taking plasma dabigatran concentrations into account (r(2) = 0.12, P = 0.02).
  
  
  CONCLUSIONS
  Of the screening coagulation assays, the TT correlated best with plasma dabigatran concentrations. Variability in fibrinogen concentrations accounts for some of the variability in the TT.
authors.affiliation: Department of Medicine, University of Otago, Christchurch, Christchurch, New Zealand; Department of Clinical Pharmacology, Christchurch Hospital, Christchurch, New Zealand.
authors.forename: Paul K L
authors.initials: PK
authors.lastname: Chin
authors.forename: David M
authors.initials: DM
authors.lastname: Patterson
authors.forename: Mei
authors.initials: M
authors.lastname: Zhang
authors.forename: Berit P
authors.initials: BP
authors.lastname: Jensen
authors.forename: Daniel F B
authors.initials: DF
authors.lastname: Wright
authors.forename: Murray L
authors.initials: ML
authors.lastname: Barclay
authors.forename: Evan J
authors.initials: EJ
authors.lastname: Begg
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000991:Antithrombins / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D001281:Atrial Fibrillation / Q000188:drug therapy*; D001562:Benzimidazoles / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D000069604:Dabigatran; D005260:Female; D005340:Fibrinogen / Q000378:metabolism*; D006801:Humans; D016014:Linear Models; D008297:Male; D008875:Middle Aged; D010314:Partial Thromboplastin Time; D011725:Pyridines / Q000493:pharmacokinetics / Q000494:pharmacology / Q000627:therapeutic use*; D013918:Thrombin Time
chemical_list: D000991:Antithrombins; D001562:Benzimidazoles; D011725:Pyridines; D005340:Fibrinogen; D000069604:Dabigatran
keywords: atrial fibrillation; blood coagulation; dabigatran; fibrinogen