Background/Purpose:

Previous hospital-based studies have shown that patients with systemic lupus erythematosus (SLE) have an increased risk of cardiovascular disease, but limited population-based data are available on the risk of deep venous thrombosis (DVT) and pulmonary embolism (PE). We estimated the population-based risk of newly recorded DVT and PE among incident cases with SLE compared to controls from the general population using physician-billing and hospitalization databases that cover the entire population of the province of British Columbia, Canada (~ 5 million).

Patients and Methods:

Our data include all visits to health professionals and all hospital admissions from Jan 1, 1990 to Dec 31, 2010 and all dispensed medications from Sept 1, 1995 to Dec 31, 2010 for all individuals. We conducted a retrospective matched cohort study among patients satisfying at least one of the following criteria: a) diagnosis of SLE in adults on at least two visits within a two-year period between Jan 1996 and Dec 2010 by a non-rheumatologist physician; b) diagnosis of SLE on at least one visit by a rheumatologist or from hospitalization. To increase specificity we excluded cases that were not confirmed by a rheumatologist if they were seen at a later point. Ten non-SLE controls matched by birth year, sex and calendar year of follow-up were selected from the general population for each case. Outcomes: incident PE, DVT, and PE or DVT events based on hospitalization records (for PE and DVT), outpatient visits (DVT) or death certificates (all outcomes). For non-fatal outcomes, we also required the use of anticoagulant medication within six-months of the event as part of all outcome definitions. We estimated relative risks (RRs) comparing SLE with age-, sex- and entry time-matched comparison cohorts, adjusting for potential cardiovascular risk factors.

Results:

Among 5,031 incident SLE cases, 72, 72 and 121 developed a first time DVT, PE, and PE or DVT event, respectively (incidence rates = 3.4, 3.4 and 5.8 per 1,000 person years, respectively) (see table). Compared with the age, sex, and entry-time-matched controls, the RRs were 5.2 (95% CI; 3.8 – 6.9), 4.6 (95% CI; 3.5 – 6.2) and 4.8 (95% CI; 3.8 – 6.0) for DVT, PE, and DVT or PE, respectively. After adjusting for covariates the results remained similar (see table). The risk of developing DVT, PE or either event was highest within the first year following diagnosis of SLE, decreasing over time and persisting after 5 years.

Conclusion:

This large population-based study indicates an increased risk of DVT and PE in patients with SLE. Our results support the need for increase monitoring for these complications in SLE patients, especially within the first year of disease onset.

Table: Risk of Incident PE, DVT or DVT or PE according to SLE Status