Background/Purpose: Testing for antiphospholipid antibodies is typically indicated for diagnosis and prognosis of antiphospholipid syndromes, however, selected patients undergo testing for other reasons.  The clinical significance of positive antibodies in this subgroup of patients is unclear.  In this study, we sought to identify patient characteristics and events associated with positive anti-cardiolipin (aCL) and anti-beta-2 glycoprotein  1 (anti-B2GP1) antibodies in a large cohort of patients.  The patients with positive results were compared to  age and gender -matched controls who had tested negative for the same antiphospholipid antibodies.

Methods: We included 110 adults and 110 age and gender-matched controls tested for aCL and anti-B2GP1 antibodies within the same calendar year (2009) at a large academic medical institution.  Clinical and laboratory data was abstracted from 1998 through 2013.

Results: Of the 110 cases,  the mean age was 54.1 years and 76 (69.1%) were female.   The majority of patients (84) were positive for  aCL-IgG (41),  IgM (25) or both (18);  29 were additionally tested for anti-B2GP1-IgG (14 positive)and IgM (15 positive).  ANA was positive in 52 patients (61%).  Thrombotic events were seen in 64 patients (59%); these included 31 (29%) with DVT/PE, 29 (27%) with stroke/TIA, 18 (22%) with any fetal loss, and 6 (6%) with any peripheral arterial events.  Thirty-six patients (33%) met criteria for APS and 23 (21%) had SLE.  Compared to controls, those with positive antiphospholipid antibodies were significantly more likely to be ANA positive (p<0.003), experience a thrombotic event (p<0.018), suffer fetal loss (p<0.022) and have SLE (p<0.001). There were non-statistically significant trends towards increased prevalence for DVT/PE (p=0.067) and peripheral arterial events (p=0.055).  No statistically significant differences were seen between the cases and controls with respect to total number of pregnancies, oral contraceptive and stroke/TIA.