Q:  What is the biggest pitfall of interpreting CRP (C-reactive protein) in suspected bacteremia?

Answer: Liver insufficiency

C-reactive protein (CRP) is a widely used marker of sepsis/bacteremia and is an independent predictor of mortality. CRP is synthesized in the liver due to inflammation. Since the CRP response in patients with liver disease is lower than in patients without liver disease, the prognostic information of initial CRP levels in patients with chronic liver disease is weak. And, the clinical management of patients with chronic liver disease and suspected infection should be based more on clinical, radiological and microbiological findings. The measurement of CRP in bacteremia is less helpful as compared with patients without liver disease.

Reference:

Janum SH, Søvsø M, Gradel KO, Schønheyder HC, Nielsen H. - C-reactive protein level as a predictor of mortality in liver disease patients with bacteremia. - Scand J Gastroenterol. 2011 Dec;46(12):1478-83.