Basophil count, a marker for disease activity in systemic lupus erythematosus.

Systemic lupus erythematosus (SLE) is a chronic multisystem autoimmune disease, with frequent flares amid remissions. Basophils contribute to the immunopathogenesis of SLE. This retrospective clinical study evaluated blood basophil count as a potential marker of SLE activity. This study included 213 patients with SLE, 70 with non-SLE chronic kidney disease (CKD), and 100 healthy volunteers. SLE disease activity was scored using the SLE Disease Activity Index (SLEDAI). Baseline and post-immunosuppressant bioparameters were compared in patients with active SLE, with second samples taken at total SLEDAI ≤4. Blood basophil counts and other conventional biomarkers were compared among the groups. Among the 213 SLE patients (192 women, 21 men; mean age 33.0 ± 12.0 years), 149 had active disease. Basophil counts were significantly lower in patients with SLE than in patients with non-SLE CKD and healthy controls (0.009 ± 0.010 vs. 0.025 ± 0.015 vs. 0.022 ± 0.010 × 10(9)/L, p <0.001), and lower in patients with active than inactive SLE (0.008 ± 0.009 vs. 0.014 ± 0.012 × 10(9)/L, p <0.001). Basophil counts in SLE patients were significantly higher after than before immunosuppressive treatment (0.021 ± 0.017 vs. 0.008 ± 0.008 × 10(9)/L, p <0.001) and correlated with total SLEDAI score (r = -0.30, p <0.001). Receiver operator curve analysis showed that basophil counts were similar to conventional markers (leukocytes, platelets, and double-stranded (ds) DNA IgG) in differentiating active from inactive SLE. These findings indicate that blood basophil counts may be a useful biomarker in evaluating SLE activity.