The potential benefit of a second C-reactive protein measurement in patients with gram-negative bacteraemia presenting to the emergency medicine department.

Background: Low C-reactive protein in acute bacterial infections could convey the erroneous impression of a mild infection. We focussed on gram-negative bacteraemia, a phenomenon frequently seen at the emergency room.

Methods: Of 2200 patients with gram-negative bacteraemia, 460 patients with first C-reactive protein <30 mg/L and 460 patients with C-reactive protein >187 mg/L were reviewed. Following exclusions, we finally investigated 229 and 289 patients with low and high C-reactive protein concentrations, respectively.

Results: The cohort was divided into low and high C-reactive protein groups. Median first C-reactive protein was 13.6 and 219.9 mg/L, respectively (interquartile range 6.4-21.6 and 195-270.1). Compared to patients with first high C-reactive protein, patients with first low C-reactive protein concentrations had a significant five-fold higher C-reactive protein level with their second test.

Conclusions: Patients with gram-negative bacteraemia can present with C-reactive protein within the range of apparently healthy individuals. A second C-reactive protein might help to avoid an erroneous decision regarding the severity of the infection.