Peripheral Eosinophil Count Associated with Disease Activity and Clinical Outcomes in Hospitalized Patients with Lupus Nephritis

Introduction: The aim of this study was to evaluate the association of peripheral eosinophil (EOS) count with disease activity and kidney outcomes in lupus nephritis (LN) patients. Methods: A total of 453 hospitalized and biopsy-proven LN patients at our hospital from 2006 to 2013 were enrolled, of which 388 patients had repeated measurements of EOS. Relationships were explored between average EOS and disease activity at baseline, using the systemic lupus erythematosus disease activity (SLEDAI) and activity index (AI) on kidney biopsy. Follow-up data were available through December 2016. The primary outcome measure was a composite of doubling of serum creatinine and end-stage kidney disease after a median follow-up of 51 months. Results: The mean age of the enrolled 388 LN patients was 33.1 +/- 10.8 years old, and 335 (86%) were female. The median average peripheral EOS count was 0.033 (0.015-0.057) x10(9)/L. Mean AI and SLEDAI score were 6.8 +/- 2.5 and 14.9 +/- 5.4, respectively. Logistic regression models showed that decreased average EOS was independently associated with higher AI (>= 6) and higher SLEDAI (>= 15) (odds ratio [OR] 0.93, 95% confidence interval [CI] 0.90-0.97; and OR 0.96, 95% CI: 0.93-0.99, respectively). There was a parabolic relationship between average EOS and the primary outcome, with hazard ratio (HR) > 1 for both levels <= 0.033 and >0.16 x 10(9)/L. Conclusion: Lower EOS count was independently associated with severe disease activity and kidney progression in LN.