Effect of long-term hydroxychloroquine on vascular events in patients with systemic lupus erythematosus: a database prospective cohort study

The incidence of thromboembolism in patients with SLE is higher than that in the general population. HCQ, widely used to treat lupus, may have vascular protective effects. The aim of this study was to determine whether long-term HCQ exposure is associated with decreased thromboembolism risk in SLE. We designed a prospective cohort study within an SLE population based on the National Health Insurance Research Database in Taiwan. We divided participants into HCQ and control groups according to HCQ prescription during the first year. These groups were defined by medication possession ratio (MPR) ⩾80% and MPR = 0%, respectively. Patients with an MPR between 0 and 80% were excluded. The primary outcome was a composite vascular event, including acute coronary syndrome, ischaemic stroke, pulmonary embolism, deep vein thrombosis and peripheral arterial disease 1 year after inclusion. We excluded patients from the cohort if they had outcomes within the first year. A total of 8397 patients were eligible for analysis. After propensity-score matching, we included 1946 patients in each group. During a mean follow-up of 7.4 years, the number of events was 139 in the HCQ group (7.1%) and 149 in the control group (7.7%). The risk of vascular events in the HCQ group was similar to that in the control group (hazard ratio = 0.91; 95% CI: 0.72, 1.15). Further subgroup analyses confirmed no statistically significant differences between the groups. Long-term HCQ appears to have no vascular protective effect in patients with SLE.