Skip to content
How It Works
Explore
Ask a Question Resources Pricing
Who It's For
Patients
Decode results, prep for appointments, weigh options.
Caregivers & advocates
Carry the research load for someone you love.
Providers & clinicians
Resources for patients in your practice.
Log In Ask a Question
PubMed This is a summary of 12 peer-reviewed journal articles Updated

Diagnosis, The 12-Week Rule, and Understanding Your Labs

At a Glance

Antiphospholipid Syndrome (APS) is diagnosed by finding persistent antibodies in your blood. Because temporary infections can cause false positives, you must have two positive tests at least 12 weeks apart for the Lupus Anticoagulant, Anticardiolipin, or Anti-beta-2 Glycoprotein I markers.

Understanding your laboratory results is the most important step in becoming an advocate for your own care. Because Antiphospholipid Syndrome (APS) can mimic other conditions, doctors use a strict set of rules to ensure an accurate diagnosis. One of the most critical things to know is that a single positive test does not mean you have APS [1].

The Three Core Markers

To diagnose APS, your care team looks for three specific types of antibodies. You may see these on your lab report:

  1. Lupus Anticoagulant (LA): The name is a historical misnomer. In a test tube, it acts like an ‘anticoagulant’ (preventing clotting), but in the human body, it actually causes the opposite effect—promoting clots [2]. It is considered one of the strongest predictors of future clotting risk [3].
  2. Anticardiolipin (aCL): This test looks for antibodies against cardiolipin, a fat found in cell membranes [4].
  3. Anti-beta-2 Glycoprotein I (aB2GPI): This test looks for antibodies against a protein that usually helps regulate clotting [5].

The 12-Week Rule

Antibodies can sometimes appear temporarily in your blood due to an infection (like a virus) or certain medications [6]. To ensure that your antibodies are persistent (always present) rather than temporary, international guidelines require that you have two positive tests at least 12 weeks apart [1][4].

Waiting three months for a second test can be anxiety-inducing. During this time, your doctor may prescribe temporary preventative measures, such as a low-dose aspirin, to keep you safe [1].

Triple Positivity: Understanding Your Risk

If your labs show that all three markers (LA, aCL, and aB2GPI) are positive, you are considered triple-positive [7]. This is an important distinction because triple-positive patients generally have a higher risk for recurring blood clots or pregnancy complications [8][9]. Because of this higher risk, triple-positive patients are typically managed with different treatment approaches.

The New Weighted Scoring (2023 ACR/EULAR)

In 2023, the medical community updated how APS is classified. While the older 2006 Sydney Criteria were simpler, the new 2023 ACR/EULAR criteria use a weighted scoring system [10][11].

  • Entry Requirement: You must have at least one positive antibody test within three years of a clinical event (like a clot or miscarriage) [11].
  • The Point System: You must score at least 3 points from clinical symptoms (like venous clots, heart valve issues, or skin rashes) AND at least 3 points from laboratory tests [11].
  • Weighting: Antibody types like IgG (which indicate a long-term immune response) or high-titer (meaning a high concentration of antibodies in your blood) carry more ‘points’ than IgM types (which can be more temporary) [11].

This new system is designed to be more precise, helping doctors distinguish between “true” APS and other similar conditions [12]. Your doctor may use these scores to help guide your treatment, discussed in Standard of Care Treatment: Warfarin, Heparin, and DOACs.

Common questions in this guide

Why do I have to wait 12 weeks for a second APS test?
Antibodies can appear temporarily in your blood due to an infection, like a virus, or certain medications. The 12-week wait ensures that your antibodies are persistently present, which is required for an accurate Antiphospholipid Syndrome diagnosis.
What does it mean to be triple-positive for APS?
Triple-positive means your lab results show all three core markers: Lupus Anticoagulant, Anticardiolipin, and Anti-beta-2 Glycoprotein I. This typically indicates a higher risk for recurring blood clots or pregnancy complications and may require a different treatment approach.
What is the Lupus Anticoagulant test?
Lupus Anticoagulant is one of the three core blood tests used to diagnose APS. Although its name includes 'anticoagulant', having this antibody actually promotes blood clots in the human body and is a strong predictor of future clotting risk.
How does the new point system for diagnosing APS work?
The 2023 ACR/EULAR criteria use a weighted scoring system where you must score at least 3 points from clinical symptoms and 3 points from lab tests. Higher levels of certain antibodies or long-term immune responses carry more points to help doctors accurately confirm true APS.

Questions to Ask Your Doctor

Curated prompts to bring to your next appointment.

  1. 1.Which specific antibodies was I positive for, and were the levels considered 'low,' 'moderate,' or 'high' titer?
  2. 2.Am I 'triple-positive,' and how does that change the type of blood thinner you recommend for me?
  3. 3.When exactly should I return for my 12-week confirmatory blood work?

Questions For You

Tap a prompt to share your answer — we'll use it plus this page's context to start a tailored conversation.

References

References (12)
  1. 1

    Emerging Treatment Models in Rheumatology: Antiphospholipid Syndrome and Pregnancy: Pathogenesis to Translation.

    Abrahams VM, Chamley LW, Salmon JE

    Arthritis & rheumatology (Hoboken, N.J.) 2017; (69(9)):1710-1721 doi:10.1002/art.40136.

    PMID: 28445926
  2. 2

    Guidance from the Scientific and Standardization Committee for lupus anticoagulant/antiphospholipid antibodies of the International Society on Thrombosis and Haemostasis: Update of the guidelines for lupus anticoagulant detection and interpretation.

    Devreese KMJ, de Groot PG, de Laat B, et al.

    Journal of thrombosis and haemostasis : JTH 2020; (18(11)):2828-2839 doi:10.1111/jth.15047.

    PMID: 33462974
  3. 3

    Anti-β2-glycoprotein I and anti-prothrombin antibodies cause lupus anticoagulant through different mechanisms of action.

    Noordermeer T, Molhoek JE, Schutgens REG, et al.

    Journal of thrombosis and haemostasis : JTH 2021; (19(4)):1018-1028 doi:10.1111/jth.15241.

    PMID: 33421291
  4. 4

    Added value of antiphosphatidylserine/prothrombin antibodies in the workup of thrombotic antiphospholipid syndrome: Communication from the ISTH SSC Subcommittee on Lupus Anticoagulant/Antiphospholipid Antibodies.

    Vandevelde A, Chayoua W, de Laat B, et al.

    Journal of thrombosis and haemostasis : JTH 2022; (20(9)):2136-2150 doi:10.1111/jth.15785.

    PMID: 35713971
  5. 5

    The (non-)sense of detecting anti-cardiolipin and anti-β2glycoprotein I IgM antibodies in the antiphospholipid syndrome.

    Chayoua W, Kelchtermans H, Gris JC, et al.

    Journal of thrombosis and haemostasis : JTH 2020; (18(1)):169-179 doi:10.1111/jth.14633.

    PMID: 31519058
  6. 6

    Antigens and Antibodies of the Antiphospholipid Syndrome as New Allies in the Pathogenesis of COVID-19 Coagulopathy.

    Serrano M, Espinosa G, Serrano A, Cervera R

    International journal of molecular sciences 2022; (23(9)) doi:10.3390/ijms23094946.

    PMID: 35563337
  7. 7

    Single or triple positivity for antiphospholipid antibodies in "carriers" or symptomatic patients: Untangling the knot.

    Bertin D, Camoin-Jau L, Veit V, et al.

    Journal of thrombosis and haemostasis : JTH 2021; (19(12)):3018-3030 doi:10.1111/jth.15518.

    PMID: 34469630
  8. 8

    Tetra positive thrombotic antiphospholipid syndrome: Major contribution of anti-phosphatidyl-serine/prothrombin antibodies to lupus anticoagulant activity.

    Cattini MG, Bison E, Pontara E, et al.

    Journal of thrombosis and haemostasis : JTH 2020; (18(5)):1124-1132 doi:10.1111/jth.14765.

    PMID: 32052568
  9. 9

    Antiphospholipid syndrome with major arterial thrombosis, presenting as pulmonary thromboembolism, cerebrovascular accident, and coronary artery disease: A case report and literature review.

    Shirani A, Daraei M, Shirani A

    Clinical case reports 2024; (12(8)):e9254 doi:10.1002/ccr3.9254.

    PMID: 39104736
  10. 10

    Performance validation of the 2023 American College of Rheumatology/European League Against Rheumatism antiphospholipid syndrome classification criteria in an antiphospholipid syndrome cohort.

    Zhao Y, Huang C, Zhou Y, et al.

    Journal of thrombosis and haemostasis : JTH 2024; (22(6)):1660-1674 doi:10.1016/j.jtha.2024.02.019.

    PMID: 38462219
  11. 11

    The 2023 ACR/EULAR Antiphospholipid Syndrome Classification Criteria.

    Barbhaiya M, Zuily S, Naden R, et al.

    Arthritis & rheumatology (Hoboken, N.J.) 2023; (75(10)):1687-1702 doi:10.1002/art.42624.

    PMID: 37635643
  12. 12

    2023 ACR/EULAR antiphospholipid syndrome classification criteria.

    Barbhaiya M, Zuily S, Naden R, et al.

    Annals of the rheumatic diseases 2023; (82(10)):1258-1270 doi:10.1136/ard-2023-224609.

    PMID: 37640450

This page explains Antiphospholipid Syndrome (APS) diagnostic testing and criteria for educational purposes only. Always consult your healthcare provider to accurately interpret your specific laboratory results.

Get notified when new evidence is published on Antiphospholipid syndrome.

We monitor PubMed for new peer-reviewed studies on this topic and email a short summary when something meaningful changes.