CRP and Sepsis: Inclusion of procalcitonin, interleukin 6 and C-reactive protein, as well as impedance aggregometry findings obtained by one of the four activators, demonstrated that impedance aggregometry findings obtained with the activators ADP (P = 0.009), collagen (P = 0.002) and thrombin receptor activating peptide (P <0.001), but not arachidonic acid, were independent predictors of severe sepsis in critical illness.