Clinical potential of C-reactive protein and procalcitonin serum concentrations to guide differential diagnosis and clinical management of pneumococcal and Legionella pneumonia

Abstract

We retrospectively analyzed the records of 61 hospitalized patients with community-acquired pneumonia (CAP) caused by Streptococcus pneumoniae or Legionella pneumophila. We found that serum procalcitonin and sodium concentrations were significantly lower, and ferritin levels were significantly higher, in patients infected with L. pneumophila than in those infected with S. pneumoniae. The ratio of C-reactive protein to procalcitonin significantly distinguished between the groups. High procalcitonin levels were associated with an adverse clinical course.

FIG. 1.

Differentiation of CAP caused by Legionella pneumophila or Streptococcus pneumoniae by inflammatory parameters. Box plots of PCT (μg/liter) and CRP (mg/dl) levels, determined for patients with S. pneumoniae (n = 37) or L. pneumophila (n = 24) pneumonia at admission (A), and of log CRP/PCT ratios (B) are shown. Groups were compared with a nonparametric Mann-Whitney U test. Differences between the respective groups were considered significant if P values were below 0.05.