Background. Platelets are involved in the pathogenesis of chronic inflammation. Thrombocyte count and platelet volume are considered as a useful activity marker of inflammatory bowel disease. The aim of the study was to compare the yield of mean platelet volume with clinical and other laboratory markers of activity in Crohn’s disease (CD). Methods and Results. A total of 56 patients with CD were investigated at time of evident clinical relapse and remission (29 males and 27 females, aged 19-68 years, mean 34.5, median 31.5 years). Complete blood count, C- reactive proteins were measured. Disease activity was assed by the Crohn’s Disease Activity Index (CDAI). Patients were checked at least twice (120 analyses were carried out in total). Thrombocytosis (above 350x109/L) was found in 32/61 (52 %) patients with clinical relapse and in 7/59 (12 %) patients with clinical remission (mean 400.7x109/l; 95%CI: 361.1–440.3x109/l; or as the case may be mean 278.6x109/l; 95% CI: 256.8–300.4x109/l). The mean platelet volume decreased (under 7.8 fL) in 19/61 (31 %) patients with clinical relapse and in 8/59 (13.5 %) with clinical remission (mean 8.333 fl; 95% CI: 7.935–8.731 fl; or as the case may be mean 9.200 fl; 95% CI: 8.824–9.576 fl). Total platelet count, CDAI and C- reactive protein were significantly increased (p<0.0001) and mean platelet volume was statistically significantly reduced (p=0.003) during clinical relapse compared with clinical remission. Conclusions. Decreased mean platelet corpuscular volume is an independent laboratory marker of clinical disease activity. However, on the basis of our study, its predictive value is inferior compared to the total platelet count, serum concentration of C- reactive protein and Crohn’s disease activity index.

        Key words: Crohn’s disease, thrombocyte, mean platelet volume.