Background: Lupus Anticoagulant (LA) is one of three laboratory criteria defined by evidence-based, international guidelines to identify antiphospholipid syndrome (APS). LA testing focuses on patients likely to have APS – those with unprovoked VTE, arterial thrombosis and pregnancy morbidity. These guidelines further detail appropriate testing following an initial positive LA to diagnose APS, including confirmation of persistent LA, anti-cardiolipin (ACL) or anti-β2-glycoprotein-1 (B2GP1) antibodies.

Aims: To audit the use and interpretation of LA at our institution against ISTH guidance (Devreese et al., 2020).

Methods: Retrospective analysis was performed on LA requests received within the Coagulation laboratory at University Hospitals Plymouth, during August 2021. The requests and results were interrogated against an audit questionnaire addressing ISTH guideline standards.

Results: A total of 65 LA requests were received; 66% had appropriate clinical indications. The majority (56.9%) were from Neurology – stroke was the most common clinical indication. LA was detected in 18.6% of requests; 2/11 by DRVVT and PTT-LA, 8/11 by PTT-LA, and 1/11 by DRVVT; 5 patients had equivocal LA results by DRVVT. All four anticoagulated patients tested using Taipan Snake Venom Time were negative. Of the 16 positive or equivocal LA results, 62.5% were repeated at >12 weeks to demonstrate persistence. ACL was included with 92.3% of LA requests, whilst B2GP1 was only requested with 53.8%; 50% of positive ACL and B2GP1 were appropriately repeated.

Conclusion(s): This small, single-institution snapshot of LA testing has provided reassurance that most requests were for appropriate clinical indications and were appropriately followed up with a second test >12 weeks; however, it was concerning that many were not accompanied by B2GP1 request. Incomplete investigation of a positive LA may lead to underdiagnosis of APS. As Neurology are the main contributor of LAS requests, their involvement in Haemostasis MDTs will help reinforce appropriate and complete testing.

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ISTH Congress Abstracts - https://abstracts.isth.org/abstract/single-centre-experience-of-lupus-anticoagulant-testing/