Meta-analysis of neutrophil-to-lymphocyte and platelet-to-lymphocyte ratio in rheumatoid arthritis

Background: We conducted a meta-analysis to review the available evidence regarding the associations between peripheral blood neutrophil-to-lymphocyte ratio (NLR) and platelet-to-lymphocyte ratio (PLR) and the presence of rheumatoid arthritis (RA). Methods: PubMed, Web of Science and Scopus, from inception to January 2018, were searched for studies reporting on NLR and PLR in RA in comparison with healthy subjects. Standardized mean difference (SMD) was calculated with a confidence interval (CI) of 95%. Results: Thirteen NLR studies (1550 RA patients and 1128 healthy controls) and 8 PLR studies (380 RA patients and 305 healthy controls) were included in the meta-analysis. NLR and PLR were significantly higher in patients with RA when compared to controls (SMD = 0.79, 95% CI 0.55-1.03; P < 0.001 and SMD = 0.66, 95% CI 0.43-0.88; P < 0.001, respectively). Conclusions: The NLR and PLR are significantly associated with the presence of RA. Further studies are required to ascertain the potential clinical use of these simple and relatively inexpensive markers in RA diagnosis.