Abstract Number: PB1938
Meeting: ISTH 2020 Congress
Background: Our institution uses dilute Russell viper venom test (dRVVT) and silica clotting time (SCT) (Instrumentation Laboratory, Bedford, MA) for lupus anticoagulant (LA) testing. We validated our diagnostic normalized ratio (NR) cutoffs at >1.2 and >1.24 for dRVVT and SCT, respectively, as per the package inserts. There was a concern for false positivity for weakly positive LA.
Aims: Investigate weakly positive LA to assess the clinical validity of these cutoffs.
Methods: We performed a retrospective review of LA results (2014-2019). Patients with a weak positive LA (SCT NR of 1.25-1.5 and dRVVT NR of 1.21-1.5) and concurrent anti-cardiolipin antibody (ACA) and anti-beta-2-glycoprotein 1 (B2GP1) antibody testing as well as those with repeat LA testing were included. We also collected pertinent clinical data, if available, which included the following: presence of provoked/unprovoked thrombosis, preeclampsia/pregnancy loss, oral contraceptive use and oral anticoagulation use during testing.
Results: Our positive LA rate was 19.4% (741 out of 3,813 samples on 3,435 patients); 134 of these patients had weakly positive LA results. Of these patients, 26/134 (19%) had both persistent LA and positive ACA/anti-B2GP1 antibodies, whereas 40/134 (30%) were negative for ACA/anti-B2GP1 antibodies and negative on repeat LA (Figure 1). 91/134 had available clinical data to analyze and, of these 91 patients, there was a high event rate in patients with weakly positive LA NR both above and below 1.35 NR (Table 1).
Conclusions: Our data shows that there is a high rate of LA persistence and ACA/anti-B2GP1 antibody positivity within the weak positive LA group (positive NR up to 1.5). Additionally, many of our patients with weak LA had clinical events, thus, suggesting that even weakly positive LA may confer a significant risk of thrombosis or pregnancy loss.
To cite this abstract in AMA style:Compton F, SoRelle J, De Simone N, Webb C, Welder D, Araj E, Shen Y-, Sarode R. Weakly Positive Lupus Anticoagulants Are also Associated with High Event Rate [abstract]. Res Pract Thromb Haemost. 2020; 4 (Suppl 1). https://abstracts.isth.org/abstract/weakly-positive-lupus-anticoagulants-are-also-associated-with-high-event-rate/. Accessed November 27, 2021.
« Back to ISTH 2020 Congress
ISTH Congress Abstracts - https://abstracts.isth.org/abstract/weakly-positive-lupus-anticoagulants-are-also-associated-with-high-event-rate/