Introduction:
Ankylosing spondylitis (AS) is a chronic inflammatory disease that can be managed with tumor necrosis factor (TNF) inhibitors. This study evaluated the effects of adalimumab, a TNF inhibitor, on inflammatory markers, including C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR). Monitoring disease activity during therapy is important for assessing treatment response.

Material and methods:
We analyzed the medical history of 28 patients with confirmed AS, treated with adalimumab. The inflammatory markers neutrophil–lymphocyte ratio (NLR), platelet–lymphocyte ratio (PLR), monocyte–lymphocyte ratio (MLR), CRP, ESR, and the Bath Ankylosing Spondylitis Disease Activity Index were assessed at the beginning of the observation (month 0) and after 3, 6, and 12 months of therapy.

Results:
The mean NLR value after 3 months of treatment was 1.48 (95% confidence interval, CI: 0.92–2.03, p < 0.001), after 6 months was 1.48 (95% CI: 0.92–2.12, p < 0.001), and after 12 months was 1.67 (95% CI: 1.08–2.30, p < 0.001). Mean MLR value after 3 months of treatment was 0.07 (95% CI: 0.03–0.13, p = 0.005), after 6 months was 0.05 (95% CI: 0.00–0.11, p = 0.101), and after 12 months was 0.06 (95% CI: 0.01–0.11, p = 0.047), showing statistical significance only after 3 and 12 months. The mean PLR value after 3 months of treatment was 52.8 (95% CI: 30.1–79.60, p < 0.001), after 6 months was 65.50 (95% CI: 31.60–83.90, p < 0.001), and after 12 months was 68.80 (95% CI: 42.70–93.70, p < 0.001).

Conclusions:
Neutrophil–lymphocyte ratio may be a useful marker of inflammation in patients with AS. Monocyte–lymphocyte ratio and PLR require further investigation. Peripheral blood tests are simple and inexpensive to perform, making hematological markers promising tools for monitoring inflammatory diseases.