C-reactive protein. A clinical marker in community-acquired pneumonia

To assess the range of plasma C-reactive protein (CRP) in patients presenting with community-acquired pneumonia and to compare the serial changes of this acute-phase protein with clinical outcome.

Prospective hospital-based study, including separate retrospective case series.

Twenty-eight consecutive patients (mean age, 60 years) admitted to our hospital with community-acquired pneumonia were studied. Serial daily plasma samples were taken and assayed for CRP, tumor necrosis factor-alpha (TNF-alpha), and interleukin 6 (IL-6). Clinical parameters, laboratory data, and response to treatment were recorded. Four other patients considered to be antibiotic failures (three empyemas, one death) were studied separately.

Two patients died. Of those who survived, mean (+/- SD) CRP values for days 1,2,3,4, and 5 were as follows: 136 +/- 43, 96 +/- 44, 53 +/- 36, 54 +/- 43, and 44 +/- 31 mg/L. CRP levels on day 1 in patients who had received antibiotics prior to hospital admission were significantly lower than those who had not, 107 +/- 42 and 152 +/- 44 mg/L (p < 0.05). CRP levels did not correlate with other laboratory parameters or with recognized predictors of mortality. A CRP value that continued to rise despite antibiotic treatment was associated with infective complications or death. Only 52% of patients had detectable TNF-alpha and 24% detectable IL-6 at some point during their hospital stay.

CRP is a sensitive marker of pneumonia. A persistently high or rising CRP level suggests antibiotic treatment failure or the development of an infective complication. These results suggest that CRP, rather than TNF-alpha or IL-6, may have a role as a clinical marker in pneumonia.