PB0950 - An APS ACTION international Core laboratory performance assessment of Lupus Anticoagulant test by Taipan and Ecarin snake venom clotting times

Monday, June 24, 2024

13:45 – 14:45 ICT

Room: Exhibition Hall

Co-Author(s)

ME

Maria Efthymiou

Senior Research Fellow
Department of Haematology, University College London
London, England, United Kingdom

Co-Author(s)

IM

Ian Mackie

Emeritus Reader in Haemostasis & Thrombosis
Department of Haematology, University College London
London, England, United Kingdom
RW

Rohan Willis

Research Director
Antiphospholipid Standardization Laboratory, Division of Rheumatology, University of Texas Medical Branch
Galveston, Texas, United States
VP

Vittorio Pengo

Professor of Cardiovascular Medicine f.r.
Department of Cardiac-Thoracic-Vascular Sciences and Public Health University of Padova
Padova, Veneto, Italy
DA

Danieli Andrade

Professor
Prof. Livre Docente da FMUSP; Associate Professor of University of São Paulo
Sao Paolo, Sao Paulo, Brazil
EB

Elisa Bison

Research Assistant
Department of Cardiac-Thoracic-Vascular Sciences and Public Health University of Padova
Padova, Veneto, Italy
ZR

Zurina Romay-Penabad

Post doctoral researcher
Antiphospholipid Standardization Laboratory, Division of Rheumatology, University of Texas Medical Branch
Galveston, Texas, United States
OA

Olga Amengual

Lecturer
Hokkaido University, Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan
Sapporo, Hokkaido, Japan
YF

Yuichiro Fujieda

Assistant Professor
Hokkaido University, Department of Rheumatology, Endocrinology and Nephrology, Faculty of Medicine and Graduate School of Medicine, Sapporo, Japan
Sapporo, Hokkaido, Japan
JV

JoAnn Vega

Research Assistant
Barbara Volcker Center for Women and Rheumatic Diseases, Hospital for Special Surgery
New York, New York, United States
MB

Maria Laura Bertolaccini

Senior Research Fellow
Academic Department of Vascular Surgery, Cardiovascular School of Medicine & Sciences, King’s College London, UK
London, England, United Kingdom
DE

Doruk Erkan

Professor
Department of Medicine, Weill Cornell Medicine
New York, New York, United States

Presenting Author(s)

Hannah Cohen, MD

University College London Hospitals, United Kingdom
London, England, United Kingdom

Co-Author(s)

oA

on behalf of APS ACTION

Group
University College London
London, England, United Kingdom

Background: Variability in lupus anticoagulant (LA) testing remains a challenge, especially in anticoagulated samples. The Taipan snake venom time (TSVT) screening and Ecarin clotting time (ECT) confirmatory tests are innately insensitive to vitamin K antagonists (VKA).

Aims: To evaluate the performance of LA testing by TSVT/ECT in VKA-anticoagulated samples between the APS ACTION international Core laboratories (CL) and examine agreement in LA status with the dilute Russell’s viper venom time (DRVVT) test.

Methods: Four CL (A-D) used the same analyser, protocol, and same lot of reagents for LA TSVT/ECT (Diagnostic Reagents Ltd). The manufacturer's cut‐off values were verified in all CL using 40 healthy subjects and George King LA Positive (+ve) and IL-LA Negative (-ve) plasmas were used for quality control (QC). In a validation exercise, each CL tested 6+ve and 6-ve blinded samples (LA status was confirmed by a second CL). Samples were also tested with DRVVT (Werfen) in 50:50 mixtures with pooled normal plasma. QCs were also tested x6 in the same run to determine intra-assay variability.

Results: All CL achieved good precision and agreement for both QCs (CV 0.7-5%) and confirmed the manufacturer’s reference range (Table 1). All CL correctly identified the blinded LA samples except for one that identified one sample as equivocal instead of +ve. In this ongoing study, agreement between DRVVT and TSVT/ECT LA status was 69.8% (in 205 samples). When results (134 samples) subcategorised by INR, agreement for INR < 2, 2-3, 3-4 and >4 was 70.6%, 66.6%, 75.7%, and 42.9%, respectively. Of the samples with disagreement, 80% (36/45) were +ve by TSVT/ECT.

Conclusion(s): Preliminary results suggest that LA -ve by DRVVT but +ve by TSVT/ECT might be explained by dilution of the inhibitor in the DRVVT. The TSVT/ECT could be used to detect LA in VKA-anticoagulated samples, without the need for mixing studies and with high specificity.