A Systematic Review and Meta-analysis of Clinical Studies on Ankylosing Spondylitis and Neutrophil to Lymphocyte Ratio

Background: Neutrophil to lymphocyte ratio (NLR) is a marker for many inflammatory diseases. Ankylosing spondylitis (AS) is among these inflammatory diseases, and many studies have compared the NLR ratio between patients with AS and healthy controls. Aim: To systematically review and analyze the available evidence about the significance of NLR values in AS. Method: Based on Meta-analysis of Observational Studies in Epidemiology (MOOSE) guidelines, we searched Embase, Pubmed, ISI Web of Science, and Scopus databases from inception to August 2020 using ("Ankylosing spondyl* " OR "Bechterew Disease" OR "Rheumatoid Spondylitis") AND ((neutrophil* AND lymphocyte*) OR NLR) as key terms of the search strategy. Data selection and extraction were conducted separately by two authors. We appraised the included articles according to the Joanna Briggs checklist. Comprehensive Meta-analysis Version 2 was used for analysis and assessment of publication bias. I2 > 75% and p-value < 0.05 were considered significant. Result: Totally, 182 studies resulted from a search in all databases. Duplicate removal, title, abstract, and full-text screening finally yielded 12 related studies, with 11 included in the meta-analysis. Quality assessment was satisfying in all studies. Pooled difference in NLR means value between patients and controls was 0.38 (95% CI: 0.24-0.52, p-value <0.0001). An I2 of 51% and a Cochran Q test p-value of <0.05 indicated moderate heterogeneity; thus, subgroup analysis had no indication. Publication bias was not significant (Funnel plot with an Egger’s intercept of -0.07; p value=0.95). Conclusion: Significant higher amounts of NLR may be strongly indicative of underlying inflammation in AS.