Diagnosis of Antiphospholipid Syndrome

Diagnosis of Antiphospholipid Syndrome

Diagnosing APS requires a combination of clinical events (such as a blood clot or pregnancy loss) and laboratory evidence of antiphospholipid antibodies. These must be present on two separate occasions at least 12 weeks apart. Read more about the diagnosis of antiphospholipid syndrome below.

Step 1: Clinical Criteria

• Vascular thrombosis – Arterial or venous blood clots (e.g. DVT, stroke, pulmonary embolism)
• Pregnancy complications:
  • Unexplained miscarriage after 10 weeks
  • Recurrent early miscarriages (3 or more)
  • Premature birth due to preeclampsia or placental insufficiency

Step 2: Laboratory Testing

Positive blood tests for any of the following:

• Lupus anticoagulant (LA)
• Anticardiolipin antibodies (IgG or IgM)
• Anti-beta-2 glycoprotein I antibodies

Tests must be positive on two occasions to confirm the diagnosis, as transient antibodies can occur after infections or other triggers.

Additional Tests

• Clotting studies (e.g. activated partial thromboplastin time – aPTT)
• Ultrasound or Doppler studies to detect DVT
• MRI or CT scan in cases of stroke or TIA
• Echocardiogram to assess heart valves

Differential Diagnosis

It’s important to distinguish APS from:

• Lupus (SLE)
• Other clotting disorders
• Inherited thrombophilias (e.g. Factor V Leiden)
• Preeclampsia or other causes of pregnancy loss

Early diagnosis helps prevent dangerous complications like stroke, miscarriage, or pulmonary embolism. Let’s now look at treatment options.

👉 [Next: Treatment for Antiphospholipid Syndrome]

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