Red Cell Distribution Width and Mean Platelet Volume in Patients With Ankylosing Spondylitis

OBJECTIVE: The results of previous studies regarding the relationship between red cell distribution width (RDW) or mean platelet volume (MPV) levels and ankylosing spondylitis (AS) are inconsistent. Therefore, we conducted this meta-analysis to systematically evaluate the associations. METHODS: The Web of Science, PubMed, and Cochrane Library (as of February 14, 2019) were used to retrieve relevant articles. Pooled standard mean difference (SMD) and its 95% confidence interval (CI) were calculated. All statistical analyses were performed using the "meta" and "metafor" packages of the R 3.5.1 software. RESULTS: Nine studies on RDW, including 775 AS patients and 972 healthy controls, and 8 studies on MPV, including 743 AS patients and 571 healthy controls, were included. The results showed that RDW levels were significantly higher in AS patients (SMD = 0.67; 95% CI, 0.30 to 1.05; p < 0.001) compared with healthy controls, whereas MPV levels (SMD = 0.01; 95% CI, -0.28 to 0.30; p = 0.929) were not significantly different from healthy controls. CONCLUSIONS: Our current study shows that the elevated levels of RDW may be associated with AS, whereas MPV levels may be not associated with AS.