Checks the entry criterion and scores six clinical and two laboratory domains to classify antiphospholipid syndrome for research, with the sources and limits shown on the page.
This page applies published classification criteria to the findings you enter. It is for research classification and clinical reference, not for diagnosis or treatment decisions. Read these limitations before relying on a result.
Source: Barbhaiya et al. 2023 (reference 1) and its supplement (reference 2). Interpretations made by AutoimmuneCalc carry no reference number.
How to use it. In each domain choose the highest level that applies to the patient, counting only findings that are otherwise unexplained. Part 1 covers clinical domains, Part 2 the laboratory domains, and Part 3 asks about timing for the entry criterion. Every domain starts at none.
Otherwise unexplained VTE confirmed by appropriate testing, such as pulmonary embolism, deep vein thrombosis of the legs or arms, splanchnic, renal vein, cerebral venous, or retinal vein thrombosis. Superficial vein thrombosis is not scored.
High risk means one or more major or two or more minor risk factors at the time of the event, when the timing and severity fit the event.
Major: active cancer that is untreated, treated without cure intent, under curative treatment (including hormonal therapy), or progressing despite curative treatment; bed-confined hospital admission with an acute illness for at least 3 days within 3 months; major trauma with fractures or spinal cord injury within 1 month; surgery under general, spinal, or epidural anesthesia for more than 30 minutes within 3 months.
Minor (need two): active systemic autoimmune disease or inflammatory bowel disease; acute severe infection; central venous catheter in the same vascular bed; hormone replacement, estrogen-containing contraceptives, or ongoing IVF; travel of 8 hours or more; BMI 30 or higher; pregnancy or up to 6 weeks postpartum; other prolonged immobilization (for example, bed-bound outside hospital for at least 3 days); surgery under general, spinal, or epidural anesthesia for under 30 minutes within 3 months.
Make every effort to find the risk-factor data. If it is truly unknown, use the retrospective option.[1]
Otherwise unexplained arterial thrombosis confirmed by appropriate testing: myocardial infarction from coronary thrombosis, peripheral, splanchnic, or retinal artery thrombosis, stroke by international definitions, and organ infarcts (kidney, liver, spleen) without a visible thrombus. Transient ischemic attack is not scored.
High risk means one or more high or three or more moderate cardiovascular risk factors at the time of the event, when the timing and severity fit the event.
High: blood pressure 180/110 mm Hg or higher; chronic kidney disease with eGFR 60 mL/min or lower for more than 3 months; diabetes with organ damage or long duration (type 1 for 20 years or more, type 2 for 10 years or more); severe hyperlipidemia (total cholesterol 310 mg/dL or higher, or LDL above 190 mg/dL).
Moderate (need three): hypertension on treatment or persistent blood pressure of 140/90 or higher; current smoking; diabetes without organ damage and of shorter duration; moderate hyperlipidemia (on treatment, or cholesterol above normal but under the severe limits); BMI 30 or higher.
If the data are unknown, use the retrospective option.[1]
Choose the highest level that applies. Findings must be otherwise unexplained. For an established item, the matching suspected definition must be fulfilled first.
Livedo racemosa: violaceous net-like mottling that is nonuniform, broken, asymmetric, and persistent. Uniform, reversible livedo reticularis is not scored.
Suspected aPL nephropathy: otherwise unexplained persistent new or worsened hypertension, proteinuria of 0.5 g per 24 hours or a protein-to-creatinine ratio of 0.5 mg/mg or more, acute renal failure, or glomerular microscopic hematuria.
Suspected pulmonary hemorrhage: respiratory symptoms plus otherwise unexplained infiltrates on imaging.
Established myocardial disease: otherwise unexplained non-ST-elevation myocardial infarction with normal coronary angiography plus cardiac MRI abnormalities, or small-vessel thrombosis on histology.[1]
Choose the highest level that applies. Findings must be otherwise unexplained, and not better explained by another condition such as lupus.
Preeclampsia: blood pressure of 140/90 mm Hg or higher on 2 occasions at least 4 hours apart after 20 weeks, with new proteinuria (0.3 mg/mg in a random urine sample, or dipstick 2+ if no quantitative result). Severe features (one or more): blood pressure of 160/110 or higher on 2 occasions; new headache unresponsive to medication; visual disturbances; pulmonary edema; liver enzymes more than twice normal or severe persistent right upper quadrant or epigastric pain; creatinine above 1.1 mg/dL or doubled; platelets below 100 x 10^9/L.
Placental insufficiency: estimated or birth weight below the 10th percentile without a fetal syndrome or genetic cause, plus one or more severe features: abnormal fetal surveillance (for example a nonreactive non-stress test); abnormal Doppler (for example absent end-diastolic flow in the umbilical artery); weight below the 3rd percentile; oligohydramnios (amniotic fluid index 5 cm or less, or deepest pocket under 2 cm).[1]
Otherwise unexplained valve disease on echocardiography. Valve dysfunction (regurgitation or stenosis) without thickening or vegetation is not scored.
Otherwise unexplained thrombocytopenia.
Tested and interpreted by the ISTH three-step method (screening, mixing, confirmation) using two screening systems, dRVVT and a sensitive aPTT. Positive if at least one system is positive after all three steps. Results from patients on anticoagulants count only if reviewed by someone with LAC expertise.
By ELISA only, and persistent (positive on at least 2 occasions at least 12 weeks apart). Moderate is 40 to 79 units and high is 80 units or more. Titers above the laboratory cut-off but below 40 units do not count. IgG and IgM are not added: choose the highest level. If two consecutive results are one moderate and one high, score moderate.
Was a positive aPL test (lupus anticoagulant, or moderate or high IgG or IgM aCL or anti-β2GPI by ELISA) documented within 3 years of the clinical criterion you scored?
Antiphospholipid syndrome (APS) is a systemic autoimmune disease in which persistent antiphospholipid antibodies accompany arterial, venous, or microvascular thrombosis, pregnancy morbidity, or other manifestations. For research, APS had been classified with the Sapporo criteria of 1999, revised in 2006, which the authors criticized for lumping together patients with very different risk profiles[1].
The 2023 ACR/EULAR criteria replace that with an entry criterion and a weighted, additive system in which the strength of each clinical finding and each antibody result matters. Their stated goal was the highest possible specificity, so that studies and trials enroll patients in whom APS is very likely[1].
Entry criterion. At least one documented clinical criterion (domains 1 to 6) and a positive aPL test within 3 years of it. If it is absent, do not classify.[1]
Additive criteria. Points are added across the eight domains, counting only the highest-weighted item in each. Classify as APS with at least 3 points from the clinical domains and at least 3 from the laboratory domains.[1]
| Domain | Levels and points |
|---|---|
| 1. VTE | With high-risk profile 1. Without 3. |
| 2. Arterial thrombosis | With high-risk profile 2. Without 4. |
| 3. Microvascular | Suspected 2. Established 5. |
| 4. Obstetric | Three or more early losses, or a fetal death at 16 to under 34 weeks alone 1. Preeclampsia or placental insufficiency with severe features 3. Both 4. |
| 5. Cardiac valve | Thickening 2. Vegetation 4. |
| 6. Hematology | Platelets 20 to 130 x 10^9/L 2. |
| 7. Lupus anticoagulant | Single positive 1. Persistent 5. |
| 8. aCL and anti-β2GPI ELISA | IgM only 1. IgG moderate 4. IgG high, one antibody 5. IgG high, both antibodies 7. |
| Result | Meaning |
|---|---|
| Entry criterion not met | No clinical criterion, no qualifying positive aPL test, or the two more than 3 years apart. The criteria should not be applied.[1] |
| Below the threshold | The entry criterion is met but clinical points or laboratory points are under 3. The patient is not classified as having APS for research. This does not rule out clinical APS.[1] |
| Classified as APS | Entry criterion met with at least 3 clinical and at least 3 laboratory points. In validation, the criteria were 99% specific against expert consensus.[1] |
In the validation cohorts, the revised Sapporo criteria were more sensitive (100% and 99%) but less specific (91% and 86%) than the 2023 criteria (83% and 84% sensitive, 99% specific)[1].
A clinical criterion is not scored when another cause is equally or more likely than APS, in the investigator’s judgment. The paper’s supplement lists examples for each item. The list is not exhaustive[2].
| Item | Examples of equally or more likely causes |
|---|---|
| Venous thromboembolism | Thoracic outlet syndrome with venous compression and upper-extremity thrombosis; genetic thrombophilia. (The traditional VTE risk factors used for scoring are not reasons for exclusion.) |
| Arterial thrombosis | Thoracic outlet syndrome with arterial compression and upper-extremity arterial thrombosis; atrial fibrillation. (The cardiovascular risk factors used for scoring are not reasons for exclusion.) |
| Livedoid vasculopathy lesions | Genetic thrombophilia such as protein C or S deficiency; systemic autoimmune disease; solid-organ or hematologic cancer. |
| aPL nephropathy (laboratory) | Active lupus nephritis; acute renal artery or vein thrombosis; diabetes; malignant hypertension; reduced renal perfusion or volume loss; infection; medications including NSAIDs, ACE inhibitors, ARBs, some antimicrobials, chemotherapy, calcineurin inhibitors, and contrast. |
| Pulmonary hemorrhage (symptoms and imaging) | Pulmonary infection, vasculitis, toxic exposure, or congestive heart failure. |
| Pulmonary hemorrhage (lavage or pathology) | ANCA-associated or drug-induced vasculitis, other systemic autoimmune disease, cryoglobulinemia, bone marrow transplant, anti-GBM disease, or IgA vasculitis. |
| Myocardial disease | Other systemic autoimmune diseases such as systemic sclerosis or vasculitis. |
| Adrenal hemorrhage or plexus thrombosis | Sepsis; medications such as tyrosine kinase inhibitors. |
| Pre-fetal death (before 10 weeks) | Known genetic abnormalities of the pregnancy, uterine malformations, poorly controlled maternal diabetes or thyroid disease, parental karyotype abnormalities. |
| Fetal death | Fetal anomalies or genetic abnormalities, feto-maternal hemorrhage, umbilical cord accidents, placental abruption, preterm rupture of membranes, congenital infection, chorioamnionitis, red cell alloimmunization. |
| Valve thickening | Active lupus; rheumatic fever. |
| Valve vegetation | Active lupus; cancer; infective endocarditis. |
| Thrombocytopenia | Active lupus; pseudothrombocytopenia; medications (myelosuppressive drugs, chemotherapy, heparin); radiation; gestational thrombocytopenia; chronic alcohol use; liver disease; splenomegaly; severe infection or sepsis; primary hematologic cancer. |
A points-based system for identifying patients with antiphospholipid syndrome (APS) for research. A patient first has to meet an entry criterion: at least one documented clinical criterion and a positive antiphospholipid antibody (aPL) test within 3 years of each other. Then points are added from six clinical domains and two laboratory domains, each weighted from 1 to 7, and the patient is classified as having APS with at least 3 clinical and at least 3 laboratory points. The criteria were published in 2023 by the ACR/EULAR APS Classification Criteria Collaborators.
No. Classification criteria define groups for studies and trials and intentionally favor specificity. In the two validation cohorts the criteria had a specificity of 99% and a sensitivity of 83% and 84%, compared with 91% and 86% specificity and 100% and 99% sensitivity for the 2006 revised Sapporo criteria. A patient can have clinical APS and not meet them, and the result should not be used by itself to start or withhold treatment.
At least one documented clinical criterion from domains 1 to 6, plus a positive aPL test (lupus anticoagulant, or moderate-to-high IgG or IgM anticardiolipin or anti-beta-2-glycoprotein I by ELISA) within 3 years of the clinical criterion. If the entry criterion is not met, the criteria should not be applied.
The domains are additive, but within each domain only the highest-weighted criterion counts. A clinical criterion should not be counted when another explanation is equally or more likely than APS.
A thrombosis that happened alongside strong provoking factors is less specific for APS, so it scores less. For venous events a high-risk profile is one major or two minor VTE risk factors, and for arterial events it is one high or three moderate cardiovascular risk factors, based on the situation at the time of the event. VTE scores 1 with a high-risk profile and 3 without, and arterial thrombosis scores 2 with and 4 without.
On standardized ELISA, moderate is 40 to 79 units and high is 80 units or more. Results above the laboratory cut-off but below 40 units are not scored. IgG and IgM are not added together, and IgM alone is worth only 1 point.
Positive on at least two occasions at least 12 weeks apart. A single positive lupus anticoagulant scores 1 point, while a persistent one scores 5.
A patient with another systemic autoimmune disease can still be classified as having APS. The paper says individual criteria should not be scored when the other disease is an equally or more likely cause, for example preeclampsia that is as likely due to lupus, or thrombocytopenia during active lupus.
Weights, definitions, and thresholds were taken from Figure 1 and Tables 1 to 3 of the paper and from its supplementary sections, then tested against every possible combination of selections (all 64,800) using a separate calculation. Every place where we interpret the paper is stated under the limitations.
Page history. October 15, 2026: page published.