Identifying a Gap in Antiphospholipid Antibody Syndrome Testing in Young Patients with Thrombotic and Obstetric Events

Abstract

Objectives Antiphospholipid antibody syndrome (APS) is an autoimmune disease characterized by thrombosis and/or certain obstetric complications in the presence of persistent antiphospholipid antibodies (aPL). In previous studies, 17% of patients <50 years old who experienced any cerebrovascular event tested positive for aPL (lupus anticoagulant (LAC), anticardiolipin (aCL), or anti-β2 Glycoprotein I (aβ2GP1)).[1] Current guidelines recommend that patients <50 with unprovoked venous thromboembolism, stroke, arterial thrombosis, or pregnancy morbidity be tested for aPL.[2,3] Here, we describe rates of aPL testing in young patients with thrombotic events (TE) (myocardial infarction (MI), stroke, deep vein thrombosis (DVT), pulmonary embolism (PE)) and obstetric events (OE) (stillbirth, preeclampsia) at the population level. Methods We assembled a retrospective cohort study using administrative data from British Columbia (BC). Our data includes outpatient and hospital visits, all dispensed medications, vital statistics, demographics, and cancer registry. Sample: We identified all patients <50 years of age with an initial MI (ICD-9 410), stroke (434), DVT (453), PE (415.1, 673.2, 639.6), stillbirth (779.9), or preeclampsia (642) between January 1997-December 2023. Outcomes: We identified all outpatient aPL testing ordered for this cohort during the study period for these patients using fee codes (LAC (90377), aCL IgG and IgM antibodies (91145, 91146), aβ2GP1 (90046, 90047)). We report the rates and mean time to outpatient testing for aPL after initial event. Results Among 112,622 patients who developed the outcomes of interest, we report 25,010 TEs, 77,725 stillbirths, and 9,847 cases of pre-eclampsia in patients <50. Of these, a minority of patients - 4.4% of MI, 28.9% of stroke, 34.2% of DVT, 36.8% of PE, 4.3% of stillbirths, and 9.6% of preeclampsia - were tested for ≥1 aPL, with median time elapsed between the event and first testing described in Table 1. Among those tested for ≥1 aPL, 21.1% of MI, 12.9% of stroke, 13.0% of DVT, 12.0% of PE, 17.7% of stillbirth, and 14.7% of preeclampsia cases were diagnosed with a systemic autoimmune rheumatic disease within ±90 days of testing; repeat TEs and OEs were also common (Table 1). Table 1: Thrombotic and Obstetric Event Incidence and Antiphospholipid Antibody Testing in BC Patients Between January 1997-December 2023 Conclusion We found low levels (<10%) and delays in aPL testing following initial thrombotic/obstetric events. A late APS diagnosis may fail to prevent subsequent recurrences of APS-associated events. References [1.] Sciascia S. Ann Rheum Dis 2015;74:2028-33 [2.] Devreese K. J Thromb Haemost 2020;18:2828-39. [3.] Barbhaiya M. Ann Rheum Dis 2023;82:1258-70.