Association of neutrophil-to-lymphocyte ratio with disease activity in systemic lupus erythematosus: A meta-analysis

Objective This study aimed to assess the relationship between the neutrophil-to-lymphocyte ratio (NLR) and systemic lupus erythematosus (SLE), with specific focus on the association between NLR and disease activity, including lupus nephritis (LN), and evaluating the correlation between NLR and the SLE Disease Activity Index (SLEDAI). Methods A systematic search of MEDLINE, Embase, and Web of Science from database inception through August 2025 was conducted. Meta-analyses compared NLR values between SLE patients and healthy controls, between active and inactive SLE, and between active LN and non-LN subgroups, with stratification by ethnicity, sample size, and publication year. Correlation coefficients between NLR and SLEDAI were pooled to assess the strength of this association. Results Thirty-one studies comprising 4,006 SLE patients and 2,576 healthy controls were included. The combined analysis showed significantly increased NLR in SLE patients versus controls (SMD = 1.051, 95% CI = 0.817–1.286, p < 0.001). Significantly higher NLR was observed in European, Asian, and Arab SLE patients relative to healthy controls within each respective subgroup, by showing significantly higher NLR in European (SMD = 1.058, 95% CI = 0.402–1.713, p = 0.002), Asian (SMD = 1.058, 95% CI = 0.839–1.278, p < 0.001), and Arab (SMD = 1.127, 95% CI = 0.707–1.547, p < 0.001) populations. Comparing disease activity, active SLE patients had notably higher NLR than those with inactive disease (SMD = 1.134, 95% CI = 0.252–2.017, p = 0.012). However, the difference in NLR between active LN and non-LN groups was not statistically significant (SMD = 0.467, 95% CI = −0.045–0.979, p = 0.074). NLR showed a significant positive correlation with SLEDAI (correlation coefficient = 0.354, 95% CI = 0.256–0.444, p < 0.001). Subgroup analysis revealed significant correlations in Asian (correlation coefficient = 0.358, 95% CI = 0.246–0.461, p < 0.001) and Arab (correlation coefficient = 0.525, 95% CI = 0.382–0.644, p < 0.001) populations. Conclusions This meta-analysis demonstrates that NLR is significantly increased in SLE patients compared to healthy controls, and that NLR is associated with greater disease activity, supported by its positive correlation with SLEDAI.