Coagulation and Thrombophilia Workup

Stroke in young or otherwise low-risk patients, recurrent thrombosis, cerebral venous sinus thrombosis, and unexplained ischemic events frequently prompt evaluation for inherited or acquired hypercoagulable states. The yield is highly dependent on patient selection: routine “hypercoagulability panels” in elderly patients with traditional vascular risk factors are usually low-yield and may produce misleading positives (false-positive lupus anticoagulant during acute illness, transient protein C/S deficiency from anticoagulation, etc.). This page covers the major hypercoagulability tests, when to order them, common interpretation pitfalls, and the practical approach to thrombophilia evaluation in neurology — including antiphospholipid syndrome, inherited thrombophilias, and the special situations of cerebral venous sinus thrombosis, young stroke, and recurrent thrombosis.

Antiphospholipid Antibodies — Antiphospholipid Syndrome (APS)

Components of the Panel

Lupus Anticoagulant (LAC)

• Functional clotting assay (DRVVT and/or aPTT-based) — measures prolongation of phospholipid-dependent clotting tests.
• Requires confirmation with mixing study and phospholipid neutralization.
• Cannot be reliably interpreted while patient is on anticoagulation (warfarin or DOACs cause false positives or interfere).

Anticardiolipin Antibodies (aCL)

• IgG and IgM isotypes.
• Quantitative (in GPL/MPL units).
• Medium-high titer required for diagnosis (>40 GPL/MPL or >99th percentile).

Anti-β2 Glycoprotein-I Antibodies (anti-β2-GPI)

• IgG and IgM isotypes.
• Medium-high titer threshold.

Diagnostic Criteria — Sydney 2006 and 2023 ACR/EULAR

The 2023 ACR/EULAR APS classification criteria are now the modern reference framework — a weighted scoring system that prioritizes persistent medium/high-titer aPL positivity and weights clinical phenotypes by their APS specificity. The historical Sydney 2006 criteria (below) remain widely cited and clinically usable, but be aware these are classification criteria for research/registry use — not a substitute for bedside diagnosis. Use persistent medium/high-titer aPL + the clinical phenotype to make the diagnosis; do not rule out APS purely because a patient fails to meet a single criterion.

Sydney 2006 Criteria (Legacy Reference)

Clinical Criteria (at least 1)

• Vascular thrombosis (venous or arterial, including stroke).
• Pregnancy morbidity: recurrent miscarriage, fetal death >10 weeks, premature birth from severe pre-eclampsia/placental insufficiency.

Laboratory Criteria (at least 1, persisting on 2 occasions ≥12 weeks apart)

• Lupus anticoagulant positive.
• Anticardiolipin (IgG or IgM) at medium-high titer.
• Anti-β2-GPI (IgG or IgM) at medium-high titer.

Triple Positivity

• Triple positive (LAC + aCL + anti-β2-GPI): highest thrombosis risk.
• Strongest indication for indefinite anticoagulation.
• Often warfarin (not DOACs) is preferred for triple-positive APS — DOACs have higher recurrence risk in this subgroup.

Neurologic Manifestations of APS

• Stroke: arterial ischemic stroke (cortical and subcortical), often in young patients.
• Recurrent TIA.
• Cerebral venous sinus thrombosis.
• Migraine-like headaches.
• Multiple sclerosis-like syndrome: subcortical lesions; APS may mimic MS.
• Cognitive impairment.
• Seizures.
• Chorea (uncommon).
• Myelitis.
• Sneddon syndrome: livedo reticularis + cerebrovascular disease.

Common Pitfalls

• False-positive LAC during acute illness: infection, inflammation, anticoagulation use.
• DOAC interference with LAC: hold DOAC before testing, or use DOAC-specific reversal in the lab.
• Low-titer aCL/anti-β2-GPI: transient, often non-specific; medium-high titers required for diagnosis.
• Pregnancy or post-partum: transient antibody fluctuations.
• Requires confirmation 12 weeks apart — single positive is insufficient.

Treatment

• Long-term anticoagulation (warfarin INR 2-3 for venous, sometimes 3-4 for arterial events).
• DOACs are inferior to warfarin in triple-positive APS.
• Hydroxychloroquine in some settings.
• Treat associated SLE if present.

Inherited Thrombophilias

Factor V Leiden (G1691A)

• Most common inherited thrombophilia in European populations (~5% heterozygous).
• Resistance to activated protein C → increased thrombosis risk.
• Venous > arterial: DVT, PE, cerebral venous thrombosis.
• Modest increase in stroke risk, especially in young patients.
• Testing: activated protein C resistance screen, or direct DNA testing.

Prothrombin Gene Mutation (G20210A)

• ~2% in European populations.
• Elevated prothrombin levels → increased thrombosis risk.
• Venous predominant, similar to factor V Leiden.
• Direct DNA testing.

Protein C, Protein S, Antithrombin Deficiencies

• Rare; severe phenotype when present.
• Venous thrombosis (DVT, PE, cerebral venous thrombosis).
• Testing pitfalls:
  • Acute thrombosis lowers all three (consumption).
  • Warfarin lowers protein C and S.
  • DOACs interfere with protein S/C assays.
  • Pregnancy lowers protein S.
  • Test 4-6 weeks after acute event and off anticoagulation when possible.

Antithrombin Deficiency

• Rare but high-risk inherited thrombophilia.
• Heparin may be less effective (antithrombin is heparin’s cofactor).
• Use larger heparin doses or argatroban; or DOAC.

Other Hypercoagulability Considerations

JAK2 V617F Mutation

• Myeloproliferative disorders (polycythemia vera, essential thrombocythemia, primary myelofibrosis).
• Associated with cerebral venous sinus thrombosis and arterial thrombosis.
• Order in CVT, atypical thrombosis, elevated hematocrit or platelet count.

PNH (Paroxysmal Nocturnal Hemoglobinuria)

• Acquired clonal hematopoietic disorder.
• Associated with cerebral venous sinus thrombosis (often unusual sites: hepatic, splenic, mesenteric).
• Flow cytometry for CD55, CD59 deficiency.

Heparin-Induced Thrombocytopenia (HIT)

• Paradoxical thrombosis with thrombocytopenia, 5-14 days after heparin exposure.
• Antibody to PF4-heparin complex.
• 4T’s score for clinical probability + serotonin release assay (gold standard) or PF4 ELISA.
• Stroke can occur with HIT.
• Treatment: stop heparin; non-heparin anticoagulant (argatroban, bivalirudin, fondaparinux).

Vaccine-Induced Immune Thrombotic Thrombocytopenia (VITT)

• Rare; described with adenoviral COVID vaccines.
• Cerebral venous sinus thrombosis with thrombocytopenia.
• Anti-PF4 antibody (similar to HIT but in absence of heparin).

Sickle Cell Disease and Trait

• Sickle cell disease: high stroke risk, especially in children; moyamoya-like vasculopathy.
• Sickle cell trait: usually benign but can cause stroke under stress (extreme exertion, hypoxia).
• Hemoglobin electrophoresis.

Practical Approach to Hypercoagulability Workup

When to Test

High-Yield Situations

• Young stroke (<55 years) without obvious cause.
• Cerebral venous sinus thrombosis.
• Recurrent thrombosis at usual or unusual sites.
• Personal or family history of unprovoked VTE in young patients.
• Recurrent pregnancy loss.
• Stroke with livedo reticularis (Sneddon syndrome).

Lower-Yield Situations (Don’t Routinely Test)

• Elderly patient with stroke + classical vascular risk factors.
• Provoked VTE (post-operative, immobilization).
• Routine evaluation in absence of suggestive history.

Timing of Testing

• Acute thrombosis distorts results: protein C, S, antithrombin all decline (consumption); LAC may falsely positive (inflammation).
• Anticoagulation distorts results: warfarin lowers protein C/S; DOACs interfere with LAC and protein S/C assays.
• Optimal timing: 4-6 weeks after acute event, off anticoagulation when clinically safe.
• Antiphospholipid antibodies should be repeated 12 weeks later for diagnostic confirmation.
• Inherited (genetic) thrombophilias (factor V Leiden, prothrombin gene mutation) can be tested at any time — not affected by acute illness or treatment.

Recommended Panel for Young Stroke / CVT

• Lupus anticoagulant, anticardiolipin, anti-β2-GPI (IgG and IgM).
• Factor V Leiden (or activated protein C resistance).
• Prothrombin gene mutation.
• Protein C, S, antithrombin activity (timing-sensitive).
• Homocysteine.
• JAK2 V617F (if CVT, atypical hematologic findings).
• PNH screen if CVT at unusual sites.
• Sickle cell screen in appropriate populations.
• HIV, syphilis (often coexisting risk factors).
• Lipid panel, HbA1c, ECG/echo.

Interpretation Pitfalls Summary

Pitfalls and Pearls

• APS diagnosis: clinical event + persistent (≥12 weeks) lab criteria.
• Triple positive APS: highest thrombosis risk; warfarin preferred over DOAC.
• LAC interference: DOACs and warfarin distort results.
• Acute thrombosis: lowers protein C, S, antithrombin (consumption); test 4-6 weeks later.
• Genetic thrombophilias: factor V Leiden, prothrombin G20210A — testable any time.
• Inherited thrombophilias: more venous than arterial; modest effect on stroke risk.
• JAK2 V617F: in CVT, atypical hematologic findings, MPNs.
• PNH: CVT at unusual sites; flow cytometry for CD55/CD59.
• HIT: thrombocytopenia + thrombosis 5-14 days post-heparin; 4T’s + assay.
• VITT: anti-PF4 in absence of heparin; CVT + thrombocytopenia post-vaccine.
• Sickle cell: stroke especially in children; transcranial Doppler screening.
• Sneddon syndrome: APS variant with livedo reticularis + cerebrovascular events.
• APS mimics MS: subcortical lesions; check antiphospholipid antibodies if MS-atypical.
• High-yield testing for VENOUS thrombosis: CVST, recurrent unprovoked DVT/PE, recurrent miscarriage. Inherited thrombophilia testing in arterial stroke is usually low-yield and rarely changes management.
• Don’t extrapolate: finding factor V Leiden or prothrombin G20210A in a young patient after arterial ischemic stroke does NOT by itself justify long-term anticoagulation — the clearest indications are APS, CVST, and recurrent venous thrombosis. Selected paradoxical-embolism contexts may warrant case-by-case judgment.
• Low-yield testing: elderly with classical vascular risk factors, provoked VTE.
• Repeat APS testing 12 weeks later for diagnostic confirmation.
• Warfarin preferred for triple-positive APS; DOACs inferior.

References

1. Miyakis S, Lockshin MD, Atsumi T, et al. International consensus statement on an update of the classification criteria for definite antiphospholipid syndrome (APS). J Thromb Haemost. 2006;4(2):295-306.
2. Pengo V, Denas G, Zoppellaro G, et al. Rivaroxaban vs warfarin in high-risk patients with antiphospholipid syndrome. Blood. 2018;132(13):1365-1371.
3. Tektonidou MG, Andreoli L, Limper M, et al. EULAR recommendations for the management of antiphospholipid syndrome in adults. Ann Rheum Dis. 2019;78(10):1296-1304.
4. Connors JM. Thrombophilia testing and venous thrombosis. N Engl J Med. 2017;377(12):1177-1187.
5. Saposnik G, Barinagarrementeria F, Brown RD Jr, et al. Diagnosis and management of cerebral venous thrombosis: a statement for healthcare professionals from the American Heart Association/American Stroke Association. Stroke. 2011;42(4):1158-1192.
6. Greinacher A. Heparin-induced thrombocytopenia. N Engl J Med. 2015;373(3):252-261.
7. Barbhaiya M, Zuily S, Naden R, et al. 2023 ACR/EULAR antiphospholipid syndrome classification criteria. Arthritis Rheumatol. 2023;75(10):1687-1702.
8. Morris JG, et al. Thrombophilia Testing After Ischemic Stroke. Stroke. 2020 (modern guidance recommending against routine testing).