Procalcitonin levels in community-acquired pneumonia - correlation with aetiology and severity.

We studied procalcitonin (PCT) levels at hospital admittance and their association with aetiology and severity in patients with community-acquired pneumonia (CAP). Median PCT concentrations were higher in bacteraemic patients than in those without bacteraemia (6.11 μg/L vs 0.34 μg/L, p = 0.0002), in patients with non-bacteraemic pneumococcal aetiology than in those infected with other classic bacteria (1.18 vs 0.18, p = 0.038), and in patients with pneumococcal as compared with viral aetiology (2.43 vs 0.24, p = 0.017). When aetiology, bacteraemia and severity according to the pneumonia severity index (PSI) were included in logistic regression analyses with PCT > 0.5 as a dependent variable, the odds ratio (OR) for non-bacteraemic pneumococcal aetiology was 5.7 (p = 0.008) and 3.0 ( p = 0.1) for PSI 4-5. A separate analysis for bacteraemia and PSI 4-5 showed an OR of 17.5 (p = 0.008) and 2.7 (p = 0.092), respectively. In CAP patients, high PCT seems to be a good marker for invasive disease and pneumococcal aetiology. As a predictor of severity it appears to be less important.