Management of Borderline Positive Lupus Anticoagulant
Repeat testing in 1 week is the only appropriate action for a borderline positive lupus anticoagulant result, and laboratories should avoid using terms like "borderline" or "dubious" in their reports. 1
Immediate Laboratory Action
The International Society on Thrombosis and Haemostasis explicitly discourages reporting results as "borderline" or "dubious" LA, and instead mandates that the laboratory comment should be limited to: "to be tested again in 1 week" 1, 2
No clinical decisions regarding anticoagulation or risk stratification should be made based on a borderline result, as this represents an indeterminate finding that requires clarification through repeat testing 1
Confirmation Testing Protocol
After the 1-week repeat test, if LA remains positive, a second confirmatory test must be performed at least 12 weeks later to establish persistent positivity, which is mandatory before making any treatment decisions 1, 3
Transient LA positivity is common and does not warrant long-term anticoagulation or indicate increased thrombotic risk 3
The testing should include both dilute Russell's viper venom time (dRVVT) and LA-sensitive activated partial thromboplastin time (APTT) as the two parallel screening tests of choice, followed by mixing and confirmatory steps 1, 4
Complete Antiphospholipid Antibody Profile
All LA results must be interpreted in the context of a complete antiphospholipid antibody profile including anticardiolipin (aCL) and anti-beta2-glycoprotein I (aβ2GPI) antibodies by ELISA 1
The presence of medium-high titers of aCL and aβ2GPI of the same isotype (most often IgG) in agreement with positive LA identifies patients at high risk for thrombosis 1
Triple positivity (LA + aCL + aβ2GPI) carries the highest thrombotic risk and should guide prophylaxis decisions 3, 4
Clinical Context Considerations
Isolated LA positivity is significantly more frequent in subjects without clinical events and may represent false-positive results, especially if mild in potency, found in elderly patients, or diagnosed for the first time 1
Testing should be avoided during acute thromboembolic events when patients may be on full-dose anticoagulants or have elevated acute-phase reactants like Factor VIII, as these interfere with accurate LA detection 1
For patients on vitamin K antagonists, testing should be performed 1-2 weeks after discontinuation or when INR is less than 1.5, with bridging using low-molecular-weight heparin (last dose >12 hours before blood draw) 1
Critical Pitfalls to Avoid
Never initiate long-term anticoagulation based on a single borderline or weakly positive LA test, as this does not meet criteria for persistent positivity and may represent transient or false-positive findings 3, 5
Do not ignore anticoagulant interference—all anticoagulants (warfarin, heparin, direct oral anticoagulants) can cause false-positive or false-negative LA results 5, 6
Avoid testing patients with elevated C-reactive protein when possible, as CRP can lead to false-positive LA results, particularly with APTT assays 6
Do not use direct oral anticoagulants (DOACs) in patients who ultimately prove to be triple-positive for antiphospholipid antibodies, as DOACs are associated with increased rates of recurrent thrombotic events compared to vitamin K antagonist therapy 7
Risk Stratification After Confirmed Persistent Positivity
For confirmed persistent LA without prior thrombosis: Consider low-dose aspirin for primary prophylaxis only if triple positive or high-titer isolated LA with systemic lupus erythematosus 3
For confirmed persistent LA with prior thrombosis: Initiate warfarin with target INR 2.0-3.0 for indefinite anticoagulation and avoid direct oral anticoagulants 3, 7
Isolated LA positivity (without aCL or aβ2GPI) has been shown to be strongly associated with vascular thrombosis (odds ratio 7.3), though the LA activity is typically weaker compared to triple-positive patients 4