Red cell distribution width, platelet-to-lymphocyte ratio, and mean platelet volume in ankylosing spondylitis and their correlations with inflammation: A meta-analysis

Objectives: To evaluate the relationship between red cell distribution width (RDW), platelet-to-lymphocyte ratio (PLR), and mean platelet volume (MPV) and ankylosing spondylitis (AS) and establish a correlation between these haematological indices and AS inflammation. Methods: We searched the Medline, Embase, and Cochrane databases, performed a meta-analysis comparing RDW, PLR, and MPV in patients with AS to controls, and examined correlation coefficients between RDW, PLR, and MPV and C-reactive protein (CRP). Results: Eleven studies were included in this meta-analysis, which revealed that RDW was significantly higher in the AS group than in the control group (standardized mean difference (SMD) = 0.687, 95% confidence interval (CI) = 0.110–1.265, p =.020). However, PLR was not significantly higher in the AS group than in the control group (SMD = 0.197, 95% CI = –0.045–0.439, p =.111). No evidence of elevated MPV in the AS group was found (SMD = –0.005, 95% CI = –0.411–0.400, p =.979). Meta-analysis of correlation coefficients revealed that RDW was positively associated with CRP (correlation coefficient = 0.327, 95% CI = 0.214–0.431, p <.001). PLR was positively associated with CRP (correlation coefficient = 0.444, 95% CI = 0.283–0.581, p <.001). In addition, the meta-analysis showed a correlation between MPV and CRP (correlation coefficient = 0.217, 95% CI = 0.080–0.346, p =.002). Conclusion: This meta-analysis demonstrated that RDW is higher in patients with AS, and a significant positive correlation exists between RDW, PLR, and MPV and CRP.