What hypercoagulability work‑up and laboratory tests should be performed in a patient with unexplained or recurrent venous thromboembolism?

Hypercoagulability Testing in Unexplained or Recurrent VTE

In patients with unprovoked venous thromboembolism, perform limited thrombophilia screening focused on antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, and anti-β2-glycoprotein I), but routine testing for inherited thrombophilias (Factor V Leiden, prothrombin mutation) is not recommended because it does not change management or improve clinical outcomes. 1

Initial Clinical Assessment

Patient Selection for Testing

Testing appropriateness should be stratified by clinical presentation 1:

High appropriateness (test these patients):

• Unprovoked VTE in patients <50 years old 1
• Thrombosis at unusual sites (cerebral, splanchnic, upper extremity) 1
• Late pregnancy loss or recurrent early pregnancy loss 1
• Any thrombosis or pregnancy morbidity in patients with autoimmune diseases (SLE, rheumatoid arthritis, autoimmune thrombocytopenia) 1

Moderate appropriateness:

• Incidentally found prolonged aPTT in asymptomatic individuals 1
• Provoked VTE in young patients 1

Low appropriateness (avoid testing):

• VTE in elderly patients 1

Recommended Laboratory Work-Up

Essential Tests (Perform in All Appropriate Patients)

Antiphospholipid antibody panel 1, 2:

• Lupus anticoagulant using dual parallel screening with both dilute Russell's viper venom time (dRVVT) AND LA-sensitive aPTT—omitting either test misses up to 55% of triple-positive cases 2
• Anticardiolipin antibodies (IgG and IgM) 1, 2
• Anti-β2-glycoprotein I antibodies (IgG and IgM) 1, 2

Basic laboratory evaluation 1:

• Complete blood count 1
• Serum calcium 1
• Liver function tests 1
• Urinalysis 1
• Chest X-ray 1

Critical Pre-Analytical Requirements

Timing of blood collection 1, 2:

• Draw blood before initiating anticoagulation or after appropriate washout period 1
• If on warfarin: test only when INR <1.5, ideally 1-2 weeks after discontinuation with LMWH bridging (last dose >12 hours before draw) 2
• If on DOACs: use commercial DOAC-removal agents before testing 2

Sample handling 1, 2:

• Use 0.109 M sodium citrate at 9:1 blood-to-anticoagulant ratio 1
• Perform double centrifugation to obtain platelet-poor plasma (<10⁷ platelets/mL) 1, 2
• If testing delayed, freeze plasma promptly and thaw at 37°C 1

Confirmation Testing

Any positive antiphospholipid antibody test MUST be repeated ≥12 weeks later to confirm persistence before making any treatment decisions 1, 2. Transient positivity is common and does not warrant long-term anticoagulation 2.

Tests NOT Routinely Recommended

Inherited Thrombophilias

Factor V Leiden and prothrombin G20210A mutation testing should NOT be performed routinely 1. The 2011 EGAPP Working Group found insufficient evidence that testing for these mutations improves clinical outcomes or changes management in patients with idiopathic VTE 1. These tests lack clinical utility because:

• They do not reliably predict VTE recurrence 1
• Results do not alter anticoagulation duration decisions 1
• Most patients with unprovoked proximal DVT warrant long-term anticoagulation regardless of thrombophilia status 1

Protein C, Protein S, and antithrombin III deficiency testing should be reserved for highly selected cases 3, 4:

• Age <45 years with recurrent VTE AND strong family history of thrombotic disorders 3, 5
• These deficiencies are found in only ~10% of young patients with VTE 5

Special Populations

Recurrent Unprovoked VTE

Patients with recurrent unprovoked VTE warrant more aggressive evaluation 1:

• Perform all tests listed above 1
• Maintain lower threshold for occult cancer screening 1
• Consider extended thrombophilia panel if first episode testing was negative 4

VTE at Unusual Sites

Upper extremity DVT: Additional screening beyond imaging is usually unnecessary because occult cancers are typically identified on the same CT/ultrasound used to diagnose the DVT 1

Splanchnic vein thrombosis 1:

• CT abdomen/pelvis (performed for diagnosis) usually sufficient for regional cancer assessment 1
• Add JAK2 V617F mutation testing—32.7% of splanchnic vein thrombosis patients carry this mutation, with ~50% developing overt myeloproliferative disorder during follow-up 1

Cancer Screening

Perform age-appropriate and gender-specific cancer screening (colon, breast, cervix, prostate) according to national guidelines 1. Extensive occult cancer screening beyond limited evaluation is not recommended for first unprovoked VTE 1.

Critical Pitfalls to Avoid

1. Never diagnose antiphospholipid syndrome on a single positive test—confirmation at ≥12 weeks is mandatory 1, 2

2. Never test for lupus anticoagulant during anticoagulation—all anticoagulants interfere with LA assays and produce false-positive/false-negative results 1, 2

3. Never use only one screening assay (dRVVT or aPTT alone)—dual parallel testing is required to avoid missing 31% of APS patients 2

4. Never initiate long-term anticoagulation based on Factor V Leiden or prothrombin mutation results alone—these do not predict recurrence risk sufficiently to guide therapy 1

5. Avoid generalized screening in asymptomatic individuals—this leads to high false-positive rates and unnecessary anxiety 1

Risk Stratification Based on Results

Triple-positive antiphospholipid antibody profile (LA + anticardiolipin + anti-β2-glycoprotein I with medium-high titers of same isotype, usually IgG) identifies highest-risk patients for thrombosis 2. Isolated persistent LA carries lower thrombotic risk 2.