Background: The diagnostic value of admission serum levels of procalcitonin (PCT) and C-reactive protein (CRP) as indicators of the etiology and prognosis was prospectively investigated.
Patients: 96 patients, 50-85 years of age, treated in the hospital for community-acquired pneumonia (CAP).
Results: On admission, all patients had elevated CRP levels (> 10 mg/l), but only 60 patients (54%) had elevated PCT levels (> 0.1 microgram/l). The severity of disease measured by APACHE II score was strongly associated with admission levels of PCT (p = 0.006), but not with CRP. Eight of nine patients with pneumonia caused by atypical agents had PCT levels < 0.5 microgram/l compared with 6/27 patients with pneumonia caused by classic bacterial pathogens, mainly Streptococcus pneumoniae (p = 0.03). No such correlation between CRP levels and etiology was found.
Conclusion: Our data indicate that in patients admitted to the hospital with CAP, measurement of PCT gives information about the severity of the disease, and may aid the physician to differentiate typical bacterial etiology from atypical etiology, and thereby to choose appropriate initial antibiotic treatment.