The relationship between blood eosinophil count and disease activity in ankylosing spondylitis patients treated with TNF-α inhibitors.

Aim: Anti-tumor necrosis factor-alpha (Anti-TNF-α) therapy has achieved an important position, are widely used for ankylosing spondylitis (AS) patients. TNF-α inhibition improves clinical outcomes and has differential effects on haematopoiesis. Information about effects on eosinophils is limited. The aim of our study is to determine the relationship between blood eosinophil counts in AS patients treated with TNF-α inhibitors.

Methods: Seventy-five patients diagnosed with AS according to modified New York criteria were enrolled in this study. Disease activity was assessed by BASDAI, and erythrocyte sedimentation rate, C-reactive protein of patients were evaluated. All data were analyzed with Spearman's correlation and Friedman's Two-Way by using SPSS version 19.0 statistical software, and p < 0.05 was considered as statistically significant.

Results: Seventy-five AS (F/M: 27/48, the mean age of 41 ± 10 years) patients were evaluated. On the 3rd month of treatment, there was a correlation between BASDAI and CRP (r = 0.32, p = 0.005), but no correlation between BASDAI and ESR (r = 0.21, p = 0.06). Blood eosinophil count was not correlated with BASDAI, ESR and CRP on pre-, post-therapy (p > 0.05). It counts lower before anti-TNF-α therapy compare with post-treatment (130/mm, 140/mm and 190/mm, respectively). There was no statistically significant difference between pre- and 3rd month (p > 0.05), while correlation was found between pre- and 6th month, and also 3rd month and 6th month (p < 0.001, p = 0.002, respectively) for blood eosinophil count.

Conclusion: To the best of our knowledge, our study is the first to evaluate blood eosinophil counts and disease activity with anti-TNF-α therapy. Blood eosinophil count may be affected by TNF-α inhibition in patients with AS.