Antiphospholipid syndrome and the relationship between laboratory assay positivity and prevalence of non-bacterial thrombotic endocarditis: A retrospective cohort study

Background: Nonbacterial thrombotic endocarditis (NBTE) is a potential complication of antiphospholipid syndrome (APS) manifesting as noninfectious lesions on one or more cardiac valves. There are limited tools to inform clinicians regarding which APS patients would benefit most from echocardiographic screening for this complication.

Objectives: We tested the hypothesis that the risk of both prevalent and incident NBTE is directly related to the number of positive laboratory assays for APS.

Patients/methods: In this single-center, retrospective, cohort study design, consecutive patients with confirmed APS seen at Mayo Clinic Rochester, MN (1/1/1993-6/26/2016), were identified by searching a centralized electronic database. Demographic data, clinical presentation, echocardiographic features, laboratory findings, and survival data were scrutinized.

Results: During the study period, 611 patients met the diagnostic criteria for APS and 386 (63%) underwent echocardiography. Of these, 58 (15%) were found to have NBTE. NBTE was more common in those with double (19.4%) and triple-positive laboratory criteria (27.0%) compared with single-positive disease (5.7%, P < .001). Survival free of NBTE diagnosis was significantly shorter in those patients with >1 positive laboratory assay (P < .01). Cox proportional hazard analysis suggests that patients with APS are more likely to be diagnosed with NBTE if they have >1 positive laboratory assay (relative risk 20.1; 95% confidence interval 1.3-316.6; P < .03).

Conclusion: Antiphospholipid syndrome carries a high prevalence of NBTE (15%). This prevalence is particularly high for patients with either double- or triple-positive laboratory criteria.