PB0158 - Antiphospholipid antibody positivity in patients presenting for clinical care at a tertiary hospital in South Africa – a single part of the antiphospholipid syndrome jigsaw.

Background: Antiphospholipid antibodies (aPLa), anticardiolipin (ACL) and anti-β2 glycoprotein-1 (anti-β2GP1), bind to cell membrane phospholipid and may result in antiphospholipid syndrome (APS), a clinical condition associated with pathogenic thrombosis and adverse obstetric outcomes. Laboratory criteria for APS include aPLa and/or the presence of a lupus anticoagulant (LA). APLa may arise de novo, in association with systemic connective tissue diseases like systemic lupus erythematosus (SLE) and possibly immunodysregulation associated with chronic infectious conditions.

Aims: This study reviewed the characteristics of patients with aPLa over a 3-month period in a tertiary hospital in South Africa.

Methods: This study was approved by the University of Witwatersrand (M231174). 1068 individual test results were reviewed for patients presenting to tertiary care.

Results: 32 patients tested positive for aPLa although with different patterns of positivity (Figure 1) – 5 patients tested positive for multiple aPLa (16%). In 3 patients, only 1 aPLa was measured. The aPLa test was equivocal in 19 patients. In only 11 patients (28%) was a laboratory-confirmed LA present. The majority of the patients who tested positive for aPLa were female with a median age of 32,5 years (range 6-83 years). The tests were most frequently requested by antenatal clinics. Five patients (16%) were HIV-infected and 5 (16%) had antinuclear antibodies.

Conclusion(s): Accurate diagnosis of APS is critical to ensuring appropriate management. Specific types and isotypes of aPLa may predispose to different outcomes and patients with an LA and both aPLa (triple-positive) are at higher risk of poor clinical outcomes. APLa testing is performed inconsistently in South Africa and newer antibodies (like phosphatidylserine) are not considered. Only 11 of the 38 patients had a confirmed LA and it is unclear how clinicians would manage patients with isolated aPLa. Careful interpretation and clinical correlation is essential to ensure that the testing yields meaningful results.