Role of interleukin-6 in mediating the acute phase protein response and potential as an early means of severity assessment in acute pancreatitis.

A number of laboratory and clinical studies have shown that interleukin-6 is the principal mediator of the acute phase protein response. In this study the relationship between serum concentrations of interleukin-6 and C-reactive protein in acute pancreatitis are examined and the ability of interleukin-6 to discriminate between severe and mild attacks is assessed. We have studied 24 patients (10 severe and 14 mild). Serum samples were collected on admission, six hourly for 48 hours and then 12 hourly for a further three days. When the areas under the curves of individual patients were compared there was a strong correlation between the total production of interleukin-6 and C-reactive protein (r = 0.73) (Spearman rank correlation) and peak interleukin-6 and C-reactive protein concentrations (r = 0.75), suggesting a close relationship between interleukin-6 and C-reactive protein production. Both on admission and peak interleukin-6 concentrations were significantly higher in patients with severe than mild disease. There was no significant difference in on admission C-reactive protein concentrations, although significant differences were seen when peak concentrations were considered. Utilising a peak interleukin-6 concentration of > 130 u/ml, we were able to distinguish between severe and mild attacks of acute pancreatitis with a sensitivity of 100% and specificity of 71%. These figures were comparable with those for peak C-reactive protein, a C-reactive protein of > 150 mg/l detecting severe attacks of acute pancreatitis with a sensitivity of 90% and specificity of 79%. In view of the fact that interleukin-6 concentrations peaked earlier than those of C-reactive protein, interleukin-6 is capable of providing comparable, but earlier severity prediction than C-reactive protein.