title: Lupus anticoagulant testing: improvements in performance in a UK NEQAS proficiency testing exercise after dissemination of national guidelines on laboratory methods.
abstract: Laboratory screening for lupus anticoagulant (LA) has been shown to be suboptimal in several studies. Guidelines have recently been published by an expert group for the British Committee for Standards in Haematology, in an attempt to standardize and improve screening procedures. The value of using screening tests conforming with these guidelines was investigated in a United Kingdom National External Quality Assessment Scheme (UK NEQAS) proficiency testing exercise. The correct diagnosis was achieved by 97% of laboratories for a LA-negative sample. However, 18.3% of centres reported a false-negative result for a sample from a LA-positive subject. A significantly higher proportion of centres that used methods conforming with the published guidelines achieved the correct diagnosis for this sample (P < 0.002, chi-square test). A wide variety of screening tests were used by laboratories in this study. Within-method agreement could be improved by the use of a common normal pooled plasma to determine ratios. However, between-method agreement was not improved by this procedure. We conclude that adoption of methods compliant with national guidelines may improve the diagnosis of LA. There is a need, however, for reference and standardization materials to ensure further improvement in the accuracy of LA methods.
authors.affiliation: UK NEQAS (Blood Coagulation), Sheffield, UK. neqas@coageqa.demon.co.uk
authors.forename: Ian
authors.initials: I
authors.lastname: Jennings
authors.forename: Mike
authors.initials: M
authors.lastname: Greaves
authors.forename: Ian J
authors.initials: IJ
authors.lastname: Mackie
authors.forename: Steve
authors.initials: S
authors.lastname: Kitchen
authors.forename: Timothy A L
authors.initials: TA
authors.lastname: Woods
authors.forename: F Eric
authors.initials: FE
authors.lastname: Preston
mesh_terms: D000925:Anticoagulants / Q000627:therapeutic use; D019983:Guideline Adherence; D017408:Guidelines as Topic; D006405:Hematology / Q000592:standards*; D006801:Humans; D007753:Laboratories / Q000592:standards*; D016682:Lupus Coagulation Inhibitor / Q000097:blood*; D008180:Lupus Erythematosus, Systemic / Q000175:diagnosis* / Q000188:drug therapy; D011786:Quality Control; D012680:Sensitivity and Specificity; D013927:Thrombosis / Q000517:prevention & control
chemical_list: D000925:Anticoagulants; D016682:Lupus Coagulation Inhibitor