Abstract
Objective: One of the most important indicators of platelet reactivity is the mean platelet volume. The platelet distribution width showing the heterogeneity of the platelet volume is a sign of platelet activation. In our study, we aim to show the correlation between ulcerative colitis activity and vitamin D, the platelet distribution width, mean platelet volume. Methods: The Truelove and Witts' severity index was used to determine ulcerative colitis activity. In accordance with the guidelines, serum 25-OH vitamin D levels of >30 ng/ml were considered as sufficient vitamin D, 20-30 ng/ml as vitamin D insufficiency, <20 ng/ml as vitamin D deficiency, and <10 ng/ml as severe vitamin D deficiency. Results: Patients with severe ulcerative colitis activity, 10% had vitamin D deficiency and 90% had severe vitamin D deficiency (p<0.001). The patients with mild ulcerative colitis activity had the highest mean platelet volume (9.5±0.44), while the patients with severe ulcerative colitis activity had the lowest mean mean platelet volume (7.1±1.52) (p<0.001). Likewise, the patients with mild ulcerative colitis activity had the highest mean platelet distribution width (17.9±1.04), while the patients with severe ulcerative colitis activity had the lowest mean platelet distribution width (14.8±2.04) (p<0.001). Conclusion: This study with a high level of evidence supports that 25-OH vitamin D has an anti-inflammatory effect in inflammatory diseases and that 25-OH vitamin D levels decrease as the disease activity increases. Moreover, the negative correlation between ulcerative colitis activity and mean platelet volume, platelet distribution width is demonstrated.

Key words: Ulcerative colitis, Vitamin D, Mean platelet volume, Platelet distribution width