Prospective study of serum and urinary nitrate levels in patients with systemic lupus erythematosus

Abstract

Objective. To study prospectively whether serum and urinary nitrate levels are related to lupus activity. Methods. Fifty patients with systemic lupus erythematosus (SLE) were studied prospectively for 2 yr. Every 4 months, the SLE Disease Activity Index (SLEDAI) was administered to the patients, and blood and 24 h urine samples were obtained; 88 healthy controls were also studied. Nitrate levels were measured by the Greiss method. Statistical analyses were performed using standard parametric and non-parametric tests, and analysis of serial measurements. Results. Twelve patients suffered infections, 12 active nephritis and 17 episodes of non-renal activity. By analysis of serial measurements, serum and urinary nitrate levels did not correlate with SLEDAI. C-Reactive protein (CRP) levels, presence of infection and creatinine clearance weakly influenced nitrate levels. Conclusions. In SLE, serum and urinary nitrate levels do not parallel lupus activity. Other variables, related or not to SLE, seem to affect these levels.