What signs and symptoms would prompt a Lupus Anticoagulant test in a patient with recurrent DVTs and cellulitis?

Signs and Symptoms Warranting Lupus Anticoagulant Testing in a Patient with Recurrent DVTs and Cellulitis

Testing for lupus anticoagulant should be performed in this 63-year-old obese male with history of multiple DVTs, as recurrent unprovoked venous thromboembolism is a high-priority indication for lupus anticoagulant testing. 1

Primary Indications for Testing

High Priority Clinical Presentations

• Unprovoked venous thromboembolism (especially with multiple episodes as in this case)
• Arterial thrombosis in patients under 50 years of age
• Thrombosis at unusual sites (cerebral, mesenteric, portal, or hepatic veins)
• Late pregnancy loss or recurrent early pregnancy loss
• Thrombosis in patients with autoimmune diseases

Moderate Priority Clinical Presentations

• Accidentally found prolonged aPTT in asymptomatic subjects
• Provoked VTE in young patients

Specific Signs and Symptoms to Monitor

Thrombotic Manifestations

• Recurrent DVTs despite adequate anticoagulation
• Arterial thrombosis (stroke, myocardial infarction, peripheral arterial occlusion)
• Thrombosis at unusual sites (cerebral sinuses, mesenteric vessels)
• Skin manifestations like livedo reticularis or skin necrosis
• Unexplained recurrent cellulitis (may be related to vascular insufficiency from thrombosis)

Laboratory Abnormalities

• Unexplained prolonged aPTT that doesn't correct with mixing studies
• Thrombocytopenia
• Presence of other autoimmune markers (ANA, anti-dsDNA)

Testing Protocol

When lupus anticoagulant testing is indicated, the International Society on Thrombosis and Haemostasis recommends:

1. Two parallel tests should be performed 1, 2:

   • dRVVT (dilute Russell's Viper Venom Time) as the first-line test
   • LA-sensitive aPTT with silica as activator

2. Testing should follow a specific protocol 2:

   • Screening phase
   • Mixing studies
   • Confirmatory testing with excess phospholipids

3. Blood collection requirements 1:

   • Collection before starting anticoagulant therapy or after adequate discontinuation
   • Fresh venous blood in 0.109 M sodium citrate (9:1 ratio)
   • Double centrifugation to minimize platelet contamination
   • Quick freezing if testing is postponed

Important Considerations

• Testing should be repeated after >12 weeks to confirm persistence, as transient positivity can occur 1, 2

• Anticoagulant therapy can interfere with testing results 3:

  • Direct oral anticoagulants (DOACs)
  • Vitamin K antagonists (warfarin)
  • Heparin

• In patients with cryptogenic stroke and history of thrombosis (as in this case), testing for antiphospholipid antibodies is reasonable 1

• The presence of lupus anticoagulant has significant treatment implications, as patients with confirmed antiphospholipid syndrome and thrombosis typically require warfarin with an INR target of 2-3 rather than DOACs 1

Pitfalls to Avoid

• Testing during acute thrombosis may yield false-positive results
• Inadequate sample preparation can affect test accuracy
• Single positive test is insufficient for diagnosis; confirmation requires repeat testing after >12 weeks
• DOACs and warfarin can cause false-positive or false-negative results, so testing ideally should be performed before anticoagulation or after temporary discontinuation when safe 3

In this 63-year-old patient with multiple DVTs and cellulitis, the history of recurrent thrombotic events strongly warrants lupus anticoagulant testing as part of a comprehensive hypercoagulability workup.