title: Evaluation of coagulation assays versus LC-MS/MS for determinations of dabigatran concentrations in plasma.
abstract: BACKGROUND
  Dabigatran is an oral direct thrombin inhibitor for which routine laboratory monitoring is currently not recommended. However, there are situations in which measurements of the drug and its effect are desirable. We therefore compared and validated different coagulation methods for assessments of dabigatran in clinical samples in relation to measurements of plasma dabigatran, without the purpose of establishing effective and safe concentrations of dabigatran in plasma.
  
  
  METHODS
  Samples were obtained from 70 atrial fibrillation patients treated with dabigatran etexilate. Plasma concentrations were measured using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and were compared with coagulation methods Hemoclot thrombin inhibitors (HTI) and Ecarin clotting assay (ECA), as well as with prothrombin time-international normalized ratio (PT-INR) and activated partial thromboplastin time (aPTT).
  
  
  RESULTS
  A wide range of dabigatran concentrations was determined by LC-MS/MS (<0.5-586 ng/mL). Correlations between LC-MS/MS results and estimated concentrations were excellent for both HTI and ECA overall (r(2) = 0.97 and 0.96 respectively, p < 0.0001), but the precision and variability of these assays were not fully satisfactory in the low range of dabigatran plasma concentrations, in which ECA performed better than HTI. aPTT performed poorly, and was normal (<40 s) even with dabigatran levels of 60 ng/mL. PT-INR was normal even at supratherapeutic dabigatran concentrations.
  
  
  CONCLUSIONS
  LC-MS/MS is the gold standard for measurements of dabigatran in plasma. Alternatively, either HTI or ECA assays may be used, but neither of these assays is dependable when monitoring low levels or to infer total absence of dabigatran. The aPTT assay is relatively insensitive to dabigatran, and normal aPTT results may be observed even with therapeutic dabigatran concentrations.
authors.affiliation: Department of Coagulation Research, Institute for Molecular Medicine and Surgery, Karolinska Institutet, & Department of Clinical Chemistry, Karolinska University Hospital, Stockholm, Sweden, Jovan.Antovic@ki.se.
authors.forename: Jovan P
authors.initials: JP
authors.lastname: Antovic
authors.forename: Mika
authors.initials: M
authors.lastname: Skeppholm
authors.forename: Jaak
authors.initials: J
authors.lastname: Eintrei
authors.forename: Elisabet Eriksson
authors.initials: EE
authors.lastname: Boija
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Söderblom
authors.forename: Eva-Marie
authors.initials: EM
authors.lastname: Norberg
authors.forename: Liselotte
authors.initials: L
authors.lastname: Onelöv
authors.forename: Yuko
authors.initials: Y
authors.lastname: Rönquist-Nii
authors.forename: Anton
authors.initials: A
authors.lastname: Pohanka
authors.forename: Olof
authors.initials: O
authors.lastname: Beck
authors.forename: Paul
authors.initials: P
authors.lastname: Hjemdahl
authors.forename: Rickard E
authors.initials: RE
authors.lastname: Malmström
mesh_terms: D000991:Antithrombins / Q000493:pharmacokinetics; D001281:Atrial Fibrillation / Q000097:blood; D001562:Benzimidazoles / Q000097:blood* / Q000493:pharmacokinetics; D001780:Blood Coagulation Tests; D002853:Chromatography, Liquid; D000069604:Dabigatran; D006801:Humans; D011725:Pyridines / Q000493:pharmacokinetics; D053719:Tandem Mass Spectrometry; D015091:beta-Alanine / Q000031:analogs & derivatives* / Q000097:blood
chemical_list: D000991:Antithrombins; D001562:Benzimidazoles; D011725:Pyridines; D015091:beta-Alanine; D000069604:Dabigatran