Why is flow cytometry used in the evaluation of antiphospholipid syndrome?

Medical Advisory BoardAll articles are reviewed for accuracy by our Medical Advisory Board
Educational purpose only • Exercise caution as content is pending human review
Article Review Status
Submitted
Under Review
Approved

Last updated: February 16, 2026 • View editorial policy

Personalize

Help us tailor your experience

Which best describes you? Your choice helps us use language that's most understandable for you.

Flow Cytometry in Antiphospholipid Syndrome Evaluation

Flow cytometry is not a standard or recommended diagnostic test for antiphospholipid syndrome (APS) according to current guidelines, but serves as an alternative detection platform for anticardiolipin (aCL) and anti-β2-glycoprotein I (aβ2GPI) antibodies in automated laboratory systems. 1

Guideline-Recommended Laboratory Testing for APS

The three mandatory tests for APS diagnosis are:

  • Lupus anticoagulant (LAC) by functional coagulation assays
  • Anticardiolipin antibodies (aCL) IgG/IgM by solid-phase assays
  • Anti-β2-glycoprotein I antibodies (aβ2GPI) IgG/IgM by solid-phase assays 1

All three tests must be performed to diagnose APS, as each detects different antibody populations with clinical significance. 1

Flow Cytometry as an Alternative Detection Platform

Approved Clinical Use

Flow cytometry has been introduced as one of several automated detection systems for measuring aCL and aβ2GPI antibodies, alongside chemiluminescence and multiplex systems. 1 These automated platforms offer advantages over traditional ELISA:

  • More harmonized working conditions with strict protocols that reduce inter-laboratory variation 1
  • Faster turnaround time and less labor-intensive processing 1
  • Simultaneous detection of all four results (aCL and aβ2GPI, both IgG and IgM) at once 1

Important Limitation

Flow cytometry-based detection systems for aCL and aβ2GPI suffer from the same standardization problems as ELISA, with high variability between commercially available assays in classifying samples as positive or negative. 1 The lack of international standards means test results can differ widely between systems. 1

Experimental Flow Cytometry Applications (Not Guideline-Recommended)

Research-Level Functional Assays

Several experimental flow cytometry approaches have been described but are not recommended for routine clinical use: 1

Annexin A5 competition assay: This flow cytometric test measures how patient antiphospholipid antibodies compete with annexin A5 binding to platelet anionic phospholipids. 2 In research studies, it showed 94% sensitivity for APS patients and was particularly sensitive for arterial thrombosis (97%) and pregnancy complications (100%). 2 However, this remains an experimental approach not validated for routine diagnosis.

Platelet activation assays: Flow cytometric measurement of platelet activation by antiphospholipid antibodies is being investigated to better characterize antibody function and link to APS pathophysiology. 3 These experimental methods are not robust enough for routine testing. 3

Phospholipid specificity testing: Flow cytometry can detect antibodies to multiple phospholipids (cardiolipin, phosphatidylserine, phosphatidylinositol, phosphatidylethanolamine) simultaneously using beads of different sizes coated with different phospholipids. 4, 5 This allows rapid detection of antibody isotype and phospholipid specificity, but clinical utility remains unproven. 4

When Flow Cytometry Is Actually Essential in APS Workup

Flow cytometry is mandatory for diagnosing inherited platelet disorders that may present with bleeding symptoms and need to be distinguished from APS-related thrombocytopenia. 6 Specifically:

  • Screening for platelet glycoprotein defects using antibodies against GPIIb/IIIa (CD41), GPIIIa (CD61), GPIb (CD42b), and GPIb/IX (CD42a) 6
  • Diagnosing Bernard-Soulier syndrome (deficient GPIb/IX expression) and Glanzmann thrombasthenia (deficient GPIIb/IIIa expression) 6
  • Evaluating granule release (α and δ granules) to detect secretion defects 6

This application is relevant when APS patients present with thrombocytopenia and the differential diagnosis includes inherited platelet disorders. 6

Clinical Bottom Line

For standard APS diagnosis, flow cytometry serves only as an alternative automated platform for measuring aCL and aβ2GPI antibodies—it does not replace or improve upon ELISA. 1 The traditional ELISA remains the standard method specified in diagnostic criteria. 1

Flow cytometry is not recommended for:

  • Lupus anticoagulant detection (functional coagulation assays remain mandatory) 1
  • Risk stratification beyond standard antibody testing 1
  • Routine functional assessment of antiphospholipid antibodies 3

The only scenario where flow cytometry adds diagnostic value in APS evaluation is when inherited platelet disorders must be excluded in patients with thrombocytopenia. 6

References

1
Guideline

Guideline Directed Topic Overview

Dr.Oracle Medical Advisory Board & Editors, 2025

3
Research

Laboratory Approaches to Test the Function of Antiphospholipid Antibodies.

Seminars in thrombosis and hemostasis, 2022

6
Guideline

Treatment of Qualitative Platelet Disorders

Praxis Medical Insights: Practical Summaries of Clinical Guidelines, 2025

Related Questions

What is the best treatment approach for a patient with suspected antiphospholipid syndrome and lupus-like symptoms, with positive PS/PT antibodies, normal C3/C4, elevated CRP, and negative ANA?
What is the appropriate workup for Antiphospholipid Antibody (APA) Syndrome?
What are the diagnostic criteria for Antiphospholipid Syndrome (APS)?
What are the diagnostic criteria for antiphospholipid syndrome (APS)?
What test should be ordered to assess the risk of thrombotic events and spontaneous abortion in a patient with Systemic Lupus Erythematosus (SLE) presenting with symmetrical small joint pain and swelling, malar rash, proteinuria, positive Antinuclear Antibody (ANA) and anti-double-stranded Deoxyribonucleic Acid (DNA) antibodies?
What is the emergency management for a patient with acute toxic inhalation (e.g., smoke, carbon monoxide, cyanide, organophosphate)?
What are the possible causes of breast-region lymphadenopathy in a 34-year-old woman?
What is the initial evaluation and management of oliguria in an older male with chronic kidney disease stage 3, benign prostatic hyperplasia, and chronic heart failure?
What is the appropriate management of acute rhinosinusitis in an adult without penicillin allergy?
I am three weeks after a miscarriage, serum β‑hCG is 6 IU/L, endometrial thickness is 8 mm, and I have occasional pink/red/brown spotting after walking; is this normal and what follow‑up is needed?
What is the therapeutic plasma concentration range for lamotrigine (Lamictal)?

Professional Medical Disclaimer

This information is intended for healthcare professionals. Any medical decision-making should rely on clinical judgment and independently verified information. The content provided herein does not replace professional discretion and should be considered supplementary to established clinical guidelines. Healthcare providers should verify all information against primary literature and current practice standards before application in patient care. Dr.Oracle assumes no liability for clinical decisions based on this content.

Have a follow-up question?

Our Medical A.I. is used by practicing medical doctors at top research institutions around the world. Ask any follow up question and get world-class guideline-backed answers instantly.

Ask Question