The grade-response relation between severity of peritonitis and serum cytokine concentrations explains Mannheim Peritonitis Index threshold.

AIM: To explore the gradient between the acute-phase response (APR) and peritonitis of differing severity. METHODS: In 202 patients with peritonitis, we determined serum concentrations of interleukin (IL)-6, IL-10, IL-13, tumor necrosis factor (TNF)-alpha, and C-reactive protein (CRP). The severity of peritonitis was graded in accordance with the Mannheim Peritonitis Index (MPI). The grade-response relation between the severity of peritonitis and each analyte was explored. RESULTS: A statistically significant association was found between the medians of severity of peritonitis and IL-6 (p < 0.025), TNF-alpha (p < 0.01), CRP (p < 0.033), IL-10 (p < 0.0001), and IL-13 (p < 0.004). Both TNF-alpha and IL-10 had a direct, and IL-13 an indirect, relation to severity, whereas CRP and IL-6 tended toward linear behavior in equilibrium. A significant association persisted between individual MPI scores and IL-6 (p < 0.002), TNF-alpha (p < 0.002), CRP (p < 0.002), and IL-10 (p < 0.001), but not IL-13 (p = 0.646). CONCLUSION: Around the mean value of grade II peritonitis, the equilibrium between pro-inflammatory and anti-inflammatory cytokines is lost. This change coincides with the 26-point threshold for the MPI.