Objective. A series of common blood tests neutrophil to lymphocyte ratio (NLR), platelet to lymphocyte ratio (PLR), and mean platelet volume (MPV) could provide a measure of systemic lupus erythematosus (SLE) activity. Methods. We searched the Medline, Embase, and Cochrane databases and performed a meta-analysis comparing NLR, PLR, and MPV in patients with SLE to controls, and examined correlation coefficients between NLR, PLR, and MPV and SLE activity based on SLE Disease Activity Index (SLEDAI) using random-effects models. Results. Nine studies were included in this meta-analysis. Meta-analysis revealed that NLR was significantly higher in the SLE group than in the control group (standard mean difference [SMD]=2.747, 95% confidence interval [CI]=1.241∼4.254, p＜0.001). PLR was also significantly higher in the SLE group (SMD=1.564, 95% CI=0.122∼3.006, p=0.034). Meta-analysis of correlation coefficients showed that both NLR and PLR were positively associated with SLEDAI (correlation coefficient=0.404, 95% CI=0.299∼0.500, p＜0.001; correlation coefficient=0.378, 95% CI=0.234∼0.505, p＜0.001). The pooled sensitivity and specificity of NLR for diagnosis of lupus nephritis were 75.1% (95% CI, 68.5∼81.0) and 72.9% (95% CI, 64.9∼80.0), respectively. The area under the curve of NLR were 0.794. However, meta-analysis indicated no elevated MPV in the SLE group and no correlation between MPV and SLE activity. Conclusion. This meta-analysis demonstrated that both NLR and PLR are higher in patients with SLE, a significantly positive correlation exists between NLR/PLR and SLE activity.

Keywords: Blood cell count, Systemic lupus erythematosus