European Journal of Cardiovascular Medicine

Primary Antiphospholipid Antibody syndrome (APS) is an immune-mediated disorder associated with antiphospholipid antibodies (aPL), which carry an increased risk of arterial and venous thrombotic events and pregnancy loss in the absence of underlying connective tissue disorders such as systemic lupus erythematosus (SLE), rheumatoid arthritis, systemic sclerosis, and others.¹

The formation of thrombi in arteries and veins is the major cause of mortality and morbidity associated with APS1. Anti-phospholipid antibodies (aPLs) mediate the autoimmune procoagulant state known as APS, but thrombosis requires a trigger to occur. This trigger can be in the form of surgery leading to prolonged immobilization, endothelial injury, infections, and oral contraceptive pills (OCP).¹

The most common sites for venous and arterial thrombosis are the lower limbs and cerebral arterial circulations, respectively. However, thrombosis can occur in any organ. The Euro-Phospholipid project reported deep venous thrombosis (DVT) as a major thrombotic event (38.9%) in a cohort of 1000 patients, followed by stroke (19.8%). ²

APS is the main culprit behind early and late pregnancy complications. Women having positive Lupus anticoagulant (LAC) or those with triple positive autoantibodies such as presence of anticardiolipin antibody (aCL)) IgG and IgM, LAC, and β-2 glycoprotein-I (anti-β-2GPI) are associated with poor prognosis. The aPL in pregnant women is associated with severe preeclampsia and stillbirth.³

Catastrophic APS (CAPS), which is usually precipitated by infection, is defined as widespread thrombosis at least in three different organs in 1 week, leading to multi-organ dysfunction in the presence of aPL and histopathological evidence of multiple thrombi. It is a life-threatening manifestation of diseases that has been linked to poor outcomes. ⁴

Laboratory tests, including enzyme-linked immunosorbent assays (ELISA), are used to identify APS. The 3 known antiphospholipid antibodies (APLAs) include anticardiolipin antibodies (aCL ab) IgG or IgM (ELISA), anti-beta-2-glycoprotein-I (anti-β2GPI) IgG or IgM (ELISA), and Lupus anticoagulants (LAC) (functional assay). Thus, this study is to describe the epidemiology, clinico-serological profile, and outcome of primary APS in a South Indian tertiary care center.

Study Design and Setting: This retrospective observational study was conducted in the Department of Clinical Immunology and Rheumatology at Sri Ramachandra Medical College and Research Institute (SRMC/SRIHER), Chennai, over a period of six years, from 2018 to 2024. The study included a cohort of 40 patients diagnosed with primary anti-phospholipid syndrome (PAPS) according to the modified Sapporo criteria.

Study Population

• Sample Size: 40 patients
• Inclusion Criteria: Patients were included if they were diagnosed with the primary anti-phospholipid syndrome (PAPS) based on the modified Sapporo criteria.
• Exclusion Criteria: Patients were excluded if they had clinical manifestations attributable to other causes, including:

• Protein C or S deficiency
• Hyperhomocysteinemia
• Factor V Leiden mutation
• Presence of other autoimmune rheumatic diseases (AIRDs)

Data Collection

The data was collected retrospectively from medical records and included the following categories:

1. Demographic Data: Age, gender, and other relevant demographic information.
2. Clinical Features: A detailed record of the clinical presentation and manifestations.
3. Laboratory Data: Laboratory tests relevant to the diagnosis and management of PAPS, specifically serum antibody levels and coagulation tests.
4. Treatment Outcome: Documentation of patient responses to treatments provided, with follow-up on clinical outcomes where available.

Diagnostic Criteria for PAPS: Patients were diagnosed with primary anti-phospholipid syndrome (PAPS) based on the modified Sapporo criteria, which requires a combination of clinical and laboratory findings. Clinical findings included thrombotic events or pregnancy morbidity, while laboratory findings included specific antiphospholipid antibodies (aPL).

Laboratory Tests

• Anti-Cardiolipin Antibodies (aCL) and Anti-β-2 Glycoprotein I Antibodies (Anti-β-2GPI)

• Method: Both anti-cardiolipin antibodies (aCL) and anti-β-2 glycoprotein I antibodies (anti-β-2GPI) were measured using Enzyme-Linked Immunosorbent Assay (ELISA).
• Antibody Types: Both IgG and IgM antibodies were assessed.
• Positivity Criteria: Titers were considered positive if:

• aCL level was above 12 GPL-U/ml.
• Anti-β-2GPI level was above 20 GPL-U/ml.
• Lupus Anticoagulant (LAC)

• Method: Lupus anticoagulant (LAC) testing was performed on patient plasma using the diluted Russell Viper Venom Test (dRVVT).
• Procedure: dRVVT testing included two steps:

• Screening Test: Initial evaluation using diluted venom to detect prolonged clotting times.
• Confirmation Step: Validation of LAC presence by neutralizing the clotting inhibitor.
• Interpretation: The normalized ratio was calculated, with a laboratory cutoff value of >1.2 considered positive for dRVVT, indicating the presence of LAC. Testing was conducted according to established guidelines and protocol

In this retrospective study, we analyzed 40 patients with primary anti-phospholipid syndrome (PAPS) at our institution. The cohort had a female-to-male ratio of 4.7:1, with 33 females and 7 males. The average age of diagnosis was 35.9 years, with patients ranging from 16 to 65 years of age.

The most frequent clinical presentation was venous thrombosis, observed in 24 patients (60%), followed by arterial thrombosis in 15 patients (37.5%), mixed arterial and venous thrombosis in 9 patients (22.5%), and obstetric complications in 5 patients (12.5%). Deep vein thrombosis (DVT) and ischemic arterial stroke were the most common venous and arterial events, respectively.

Among diagnostic tests, the Lupus Anticoagulant (LAC) test was the most commonly positive test, found in 22 patients (55%), followed by β-2 glycoprotein I (β-2GPI) antibody in 19 patients (47.5%), and anti-cardiolipin (aCL) antibody in 15 patients (37.5%).

In total, five patients in the study presented with catastrophic anti-phospholipid syndrome (CAPS), of whom one died. Non-thrombotic manifestations such as thrombocytopenia and hemolytic anemia were also observed. Obstetric complications and thrombosis recurrence were each found in 5 patients (12.5%).

Figure 1: Venous Thrombosis Events (n=40)

Figure 1: Venous thrombosis was the most common clinical presentation, observed in 60% of patients. The predominant venous events included deep vein thrombosis (47.5%) and pulmonary thromboembolism (27.5%).

Figure 2: Arterial Thrombosis Events (n=40)

Arterial Thrombosis: Arterial thrombosis was observed in 37.5% of patients, with ischemic stroke (27.5%) and acute myocardial infarction (15%) being the most frequent arterial events.

Table 1: Characteristics of CAPS Patients

Out of five patients with the catastrophic anti-phospholipid syndrome (CAPS), three were triple positive for anti-phospholipid antibodies (APLA) and two were positive for LAC alone. One patient succumbed to the disease, while the remaining four survived after intensive treatment.

Table 2: Frequency of Positive Diagnostic Tests in Patients with PAPS (n=40)

The Lupus Anticoagulant (LAC) test had the highest positivity rate (55%) among PAPS patients, followed by β-2 glycoprotein I (47.5%) and anti-cardiolipin antibodies (37.5%).