Background: Hematological markers such as the neutrophil-lymphocyte ratio (NLR), monocyte-lymphocyte ratio (MLR), and platelet-lymphocyte ratio (PLR) are reliable indicators of inflammation. This study aims to investigate the potential role of these markers in assessing disease activity and treatment response in biologic-naive Ankylosing Spondylitis (AS) patients following the initiation of biological agents. Materials and methods: We designed this study as a retrospective cohort study with data obtained from a single center. The Bath Ankylosing Spondylitis Disease Activity Index (BASDAI) and The Bath Ankylosing Spondylitis Functional Index (BASFI) were used to evaluate disease activity and functional status of AS patients. Laboratory results at baseline, 3rd, 6th, and 12th months were documented. We calculated hematologic inflammatory markers for each visit. Mean platelet volume (MPV) and red cell distribution width (RDW) were also noted. Results: 54 biologic-naive patients with AS were included in this study. These inflammatory markers, except RDW, decreased over time. BASDAI, BASFI, CRP and ESR were significantly lower at 3rd, 6th, and 12th months compared to baseline values (all p < 0.001). Furthermore, NLR, PLR, and MLR showed a statistically significant decrease at 3rd, 6th, and 12th months compared to baseline values (all p < 0.001). However, when comparing the values at the 3rd, 6th, and 12th months, no statistically significant differences were observed. We also found no correlation between hematological inflammatory markers and BASDAI scores, despite observing some correlations between hematological markers and acute phase reactants. Conclusion: These markers could be valuable assessment tools for indicating disease activity and monitoring patients with AS after initiating biological treatment.
