Antiphospholipid Syndrome Laboratory Testing

November 2023
Ampath | ampath.co.za

Overview

Antiphospholipid syndrome (APS) is an acquired autoimmune disorder characterised by:

• Recurrent venous or arterial thrombosis
• Pregnancy morbidity
• Persistent presence of antiphospholipid antibodies (aPL)

APS can be:

• Primary (occurring in isolation)
• Secondary, most commonly associated with systemic lupus erythematosus (SLE)

When to Suspect APS

Suspicion should arise in patients with:

• Unprovoked or recurrent thrombosis (especially in younger individuals)
• Adverse pregnancy outcomes
• Other potential signs such as:
  • Livedo reticularis
  • Mild thrombocytopenia
  • Heart valve disease
  • Kidney disease
  • Neurological symptoms

Diagnostic Approach

Step-by-Step:

1. Clinical suspicion of APS
2. Exclude other causes of thrombosis or pregnancy loss
3. Perform APS profile testing
4. If any result is positive, repeat testing ≥12 weeks later to confirm persistence

Recommended Routine Laboratory Tests

• Full Blood Count (FBC)
• Coagulation Studies (PT and aPTT)
• Renal Function Test
• Urinalysis
• Autoimmune Screen:
  • ANA
  • dsDNA
  • ENA

APS Profile Testing Includes

• Lupus Anticoagulant (LA)
• Antiphospholipid antibodies:
  • IgG and IgM antibodies to:
    • Cardiolipin (aCL)
    • Beta-2-glycoprotein I (anti-β2GPI)
    • Phosphatidylserine

International Diagnostic Criteria (Sydney/Sapporo Criteria)

To diagnose APS, at least one laboratory and one clinical criterion must be met.
Criteria must be within a 5-year window.

Laboratory Criteria:

• Lupus anticoagulant positive on two occasions ≥12 weeks apart
• Anticardiolipin antibodies (IgG or IgM):
  • Medium/high titres:
    40 GPL or MPL units
    • Or >99th percentile
  • On two occasions ≥12 weeks apart

Clinical Criteria:

Thrombosis:

• One or more objectively confirmed:
  • Venous thrombosis
  • Arterial thrombosis
  • Small vessel thrombosis
    (Must be in the absence of significant vessel wall inflammation)

Pregnancy complications:

• One or more unexplained deaths of a morphologically normal fetus at >10 weeks
• One or more premature births before 34 weeks due to:
  • Pre-eclampsia
  • Eclampsia
  • Placental insufficiency
• Three or more spontaneous pregnancy losses before 10 weeks without another identifiable cause

APS Profile Test Information

• Mnemonic: LUP
• Specimen Type: Venous blood
• Collection Tubes Required:
  • 2 citrate tubes (CO1 x 2)
  • 1 serum-separating tube (SST) (SO1 x 1)
• Transport Instructions:
  • Citrate samples must reach the lab within 4 hours
  • If delayed: centrifuge and freeze
• Turnaround Time: 24 hours (weekdays only)

📌 Contact your local Ampath representative for more information or support with APS testing.