Objectives To evaluate whether hyperuricemia is independently associated with cardiovascular events in a cross-sectional study of Chinese patients with SLE.
Methods Consecutive patients who fulfilled ≥4 ACR criteria for SLE were recruited. Fasting blood was taken for serum urate level, along with other atherosclerosis risk factors that included glucose, total, LDL, HDL cholesterol and triglyceride. Patients were assessed for body mass index (BMI), waist circumference and the presence of the metabolic syndrome (MetS) as defined by the updated joint consensus criteria, using the Asian criteria for central obesity. The 4-variable estimated glomerular filtration rate (eGFR) was also calculated. Patients were stratified according to different serum urate levels: <0.35mmol/L, 0.35–0.48mmol/L, 0.48–0.60mmol/L and >0.60mmol/L. Comparison of the prevalence of vascular risk factors, the MetS and arterial thrombotic events (acute coronary syndrome, stroke, peripheral vascular event) was made among patients with different levels of urate. Cox regression models were established to study whether hyperuricemia was independently associated with arterial events with adjustment of demographic variables, eGFR, vascular risk factors and the antiphospholipid (aPL) antibodies.
Results 485 SLE patients were studied (93% women; mean age 46.2±14 years); 259 (53%) had renal involvement and 73 (15%) had chronic kidney disease (stage ≥3). Hyperuricemia (urate >0.35mmol/L) was present in 185 (38%) patients. The number of patients who had serum urate levels of 0.35–0.48, 0.48–0.60 and >0.60mmmol/L was 131 (27%), 40 (8.7%) and 14 (2.9%), respectively. Patients with hyperuricemia, compared with those without, were more likely to be men (14% vs 3%; p<0.001), have renal disease (72% vs 42%; p<0.001), hypertension (34% vs 15%; p<0.001), lower eGFR (73.4±34 vs 101±27; p<0.001) but longer SLE duration (14.3±8.7 vs 12.2±7.4 years; p=0.006). The LDL-cholesterol level (3.34±1.37 vs 2.89±1.51mmol/L; p=0.001), triglyceride level (1.62±0.77 vs 1.29±0.78mmol/L; p<0.001), BMI (23.2±4.5 vs 22.3±3.8kg/m2; p=0.04) and occurrence of the MetS (22% vs 12%; p=0.007) were significantly higher in patients with hyperuricemia. Over an observation of 12.9±8.0 years, 50 acute arterial events (17 acute coronary syndrome; 24 stroke, 7 peripheral vascular event and 2 retinal artery thrombosis) developed in 47 patients. Acute coronary events were significantly more common in patients with hyperuricemia than those without (7.6% vs 1.0%; p=0.001). Cox regression analysis revealed that HDL<1.0mmol/L (HR 3.44 [1.62–7.27]; p=0.001], lupus anticoagulant (HR 3.84 [1.92–7.65]; p<0.001) and age of SLE onset (1.03 [1.004–1.05] per year; p=0.02) were independently associated with arterial thrombosis. In separate regression models, elevated urate levels (>0.35, >0.48 or >0.60mmol/L) were not significantly associated with arterial events after adjustment for age, sex, eGFR, smoking, LDL-cholesterol, HDL-cholesterol, triglyceride, BMI, diabetes mellitus, hypertension and the apL antibodies.
Conclusions In patients with SLE, hyperuricemia was associated with atherosclerotic risk factors, the MetS and acute coronary events. However, in multivariate regression models, hyperuricemia was not an independent risk factor for any arterial events after adjustment for confounding factors.
Disclosure of Interest None declared