title: The laboratory diagnosis of lupus anticoagulant in patients on oral anticoagulation.
abstract: Laboratory-specific cut-off lupus ratios (LR), above which a plasma is judged positive for lupus anticoagulant (LA), were established for both activated partial thromboplastin time-based and dilute Russell viper venom time-based methods. The validity of using these cut-off values to determine the presence of LA in patients on oral anticoagulation (OAC) was assessed. A cohort of 40 patients (23 male and 17 female), aged 22-84 years (mean 52 years) were tested for LA at the time of a thrombotic event. Repeated testing was performed after the same patients were treated with OAC (international normalized ratio 2.0-3.5). For 36 patients (90%), LA status was unchanged pre- and on-OAC. Thirteen of the 40 patients (32.5%) were positive for LA both pre- and on-OAC. Of the 27 patients negative for LA pre-OAC, 23 remained negative on-OAC. The four discordant results were interesting in that LA positivity was demonstrated only after the patient was stable on-OAC. In our cohort of 40 patients, there was a trend for LRs to decrease on-OAC, but this did not reach statistical significance. The subset (4) went against this trend and became positive after the thrombotic event.
authors.affiliation: Pacific Laboratory Medicine Services, Royal North Shore Hospital, Sydney, Australia. maboud@nsccahs.health.nsw.gov.au
authors.forename: M R
authors.initials: MR
authors.lastname: Aboud
authors.forename: C
authors.initials: C
authors.lastname: Roddie
authors.forename: C M
authors.initials: CM
authors.lastname: Ward
authors.forename: L
authors.initials: L
authors.lastname: Coyle
mesh_terms: D000284:Administration, Oral; D000925:Anticoagulants / Q000008:administration & dosage*; D015331:Cohort Studies; D003627:Data Interpretation, Statistical; D005260:Female; D006801:Humans; D016682:Lupus Coagulation Inhibitor / Q000097:blood*; D008297:Male; D008875:Middle Aged; D020246:Venous Thrombosis / Q000097:blood* / Q000175:diagnosis* / Q000188:drug therapy
chemical_list: D000925:Anticoagulants; D016682:Lupus Coagulation Inhibitor