title: Screening for lupus anticoagulants in patients treated with vitamin K antagonists.
abstract: BACKGROUND
  The dRVVT test for detecting lupus anticoagulants (LA) is difficult to interpret when patients are treated with vitamin K antagonists (VKA).
  
  
  METHODS
  We performed LA testing in 33 VKA-treated patients with definite antiphospholipid syndrome (APS) and compared the results with 100 controls subjects not receiving VKA and 110 APL-negative patients anticoagulated for reasons other than APS.
  
  
  RESULTS
  Compared with the dRVVT ratio before the initiation of VKA therapy, a higher cutoff value, defined as the 99th percentile, was established for VKA-treated patients with INR values between 2.0 and 3.5. A dRVVT ratio of >1.7 yielded a sensitivity of 81.3%, specificity of 99.1%, and positive and negative predictive values of 98.7% and 85.8%, respectively, for detecting LA. Cohen's kappa coefficient indicated good agreement for the dRVVT ratio obtained from testing with and without VKA treatment (κ = 0.813; 95% CI: 0.773-0.853), which was higher (κ = 0.941; 95% CI: 0.917-0.965) when the LA diagnosis was based on the results of both the dRVVT and a second test system (i.e., Mixcon-LA assay).
  
  
  CONCLUSIONS
  Lupus anticoagulants testing in VKA-treated patients with APS according to current guidelines appears to be possible for the majority of patients without discontinuing anticoagulant therapy.
authors.affiliation: Division of Vascular Medicine, Department of Internal Medicine, Goethe University Hospital, Frankfurt/Main, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Isert
authors.affiliation: Haemophilia Center, Department of Internal Medicine, Goethe University Hospital, Frankfurt/Main, Germany.
authors.forename: W
authors.initials: W
authors.lastname: Miesbach
authors.affiliation: Division of Haemostaseology, Department of Internal Medicine, Goethe University Hospital, Frankfurt/Main, Germany.
authors.forename: G
authors.initials: G
authors.lastname: Stoever
authors.affiliation: Division of Haemostaseology, Department of Internal Medicine, Goethe University Hospital, Frankfurt/Main, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Lindhoff-Last
authors.affiliation: Division of Vascular Medicine, Department of Internal Medicine, Goethe University Hospital, Frankfurt/Main, Germany.|Praxis am Grueneburgweg, Medical Practice of Angiology and Haemostaseology, Frankfurt/Main, Germany.
authors.forename: B
authors.initials: B
authors.lastname: Linnemann
mesh_terms: D000328:Adult; D000368:Aged; D000925:Anticoagulants / Q000627:therapeutic use*; D016736:Antiphospholipid Syndrome / Q000097:blood* / Q000150:complications / Q000175:diagnosis / Q000188:drug therapy*; D001777:Blood Coagulation / Q000187:drug effects; D001780:Blood Coagulation Tests / Q000379:methods / Q000592:standards; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood*; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014812:Vitamin K / Q000037:antagonists & inhibitors*; D055815:Young Adult
chemical_list: D000925:Anticoagulants; D016682:Lupus Coagulation Inhibitor; D014812:Vitamin K
keywords: Lupus anticoagulants; anticoagulation; antiphospholipid syndrome; dilute Russell's viper venom time; vitamin K antagonist