C-reactive protein in community-acquired sepsis: you can teach new tricks to an old dog

Assessment of clinical resolution criteria and response to treatment in sepsis is a complex and unresolved issue. The intricate pathophysiology limits our ability to anticipate outcomes and to effectively use tools to improve the decision-making process in sepsis. In the previous issue of Critical Care, Póvoa and colleagues [1] provide us clinically relevant data on how we can obtain the best information when using a biomarker to assess clinical response and identify relevant evolution patterns in septic patients.This large observational multicenter study evaluated serial C-reactive protein (CRP) measurements to describe the clinical course of community-acquired sepsis in patients admitted to the ICU. Instead of using a traditional approach for biomarker evaluation (that is, analyzing mean differences of absolute values), the authors performed a complex analysis of serial measurements of CRP within 5 days of ICU admission. As early as day 3, a clinical response pattern was identified as a function of CRP variation and was assessed as the ratio between CRP value on each day and the baseline CRP. This approach of dynamic evaluation using the CRP ratio was used in different studies involving patients with ventilator-associated pneumonia (VAP) to assess an association between CRP variation and appropriateness of antibiotic therapy [2,3]. Although CRP is frequently criticized because of its relative unspecific increases occurring as a result of several non-infectious inflammatory stimuli, CRP values usually present a sharp decrease after the withdrawal of the inflammatory injury [4]. Therefore, when the patient is his or her own control (that is, a relative variation in the same patient is considered a marker for clinical response), we may control for the potential differences secondary to different base-line inflammation response level and assess the variation occurring according to the actual resolution of infectious stimulus.In the original study evaluating clinical r