Results

IL-6 was one of the various inflammatory mediators which was increased most frequently (> or= 90%) and markedly in active Crohn's disease. From the acute phase proteins and the other conventional markers of disease activity studied, SAA proved most sensitive (> or= 90%) and also showed the closet correlation with CDAI and histological activity. IL-6 was tightly linked to both SAA and CRP (r approximately 0.8). SAA and CRP were closely associated with each other (r= 0.88). The pattern and degree of increases in circulating inflammatory mediators was very similar in patients with ulcerative colitis and Crohn's disease. The increases of all inflammatory mediators and acute phase proteins gradually decreased during medical therapy. During follow-up IL-6 and SAA proved most useful to indicate a relapse of Crohn's disease.

Conclusions

Measurements of circulating IL-6 and SAA proved most useful for clinical monitoring of the activity of Crohn's disease and ulcerative colitis and thus have advantages over conventional markers such as CRP, sedimentation rate and platelet count. IL-6 is probably the main cytokine factor responsible for hepatic induction of acute phase proteins in Crohn's disease. Measurements of circulating levels of all the inflammatory mediators studied are not useful at all for differentiation between Crohn's disease and ulcerative colitis.