C-reactive protein in patients with bacteremia.

Quantitative measurement of C-reactive protein (CRP) in serum has been proposed as a sensitive and, for some populations, a specific indicator of infection. To determine whether early measurement of CRP in serum could differentiate patients with bacteremia from a control group of patients whose blood cultures yielded contaminants, we measured CRP concentrations quantitatively by rate nephelometry in serum samples that had been obtained from patients on the same day as blood samples that yielded bacteria or fungi. Of the 36 episodes of bacteremia, 3 (8.5%) occurred in patients with normal concentrations of CRP in serum and 2 (5.5%) in patients with minimally elevated levels. Of the 21 episodes associated with contaminated blood cultures, only 2 (9.5%) occurred in patients with normal CRP levels. Of the patients with marked elevations of CRP (greater than 10 mg/dl), 18 (86%) had infection, although not all of these patients had bacteremia. We conclude that a normal concentration of CRP in serum does not eliminate the possibility of bacteremia. Moderate elevations (1 to 10 mg/dl) of CRP levels are common in both patients with contaminated blood cultures and in those with bacteremia. If the CRP concentration in serum is greater than 10 mg/dl and if other causes of marked elevations of CRP levels are eliminated, CRP concentration in serum may be a relatively specific indicator of infection. However, elevations of CRP concentrations are neither completely sensitive nor specific for detecting infection in patients with bacteremia.