Differentiation of bacterial and viral community-acquired pneumonia in children

Microbe-specific diagnosis of pediatric community-acquired pneumonia (CAP) and the distinction between typical-bacterial, atypical-bacterial and viral cases are difficult. The aim of the present study was to evaluate the role of four serum non-specific inflammatory markers and their combinations, supplemented by chest radiological findings, in the screening of bacterial etiology of pediatric CAP.

Serum procalcitonin (PCT), serum C-reactive protein (CRP), blood erythrocyte sedimentation rate (ESR) and white blood cell (WBC) counts were determined in 101 children with CAP, all confirmed on chest radiograph. Evidence of etiology was achieved in 68 patients (67%) mainly using a serologic test panel including 15 pathogens.

For the combination of CRP > 100 mg/L, WBC count > 15 x 10(9)/L, PCT > 1.0 ng/mL and ESR > 65 mm/h, the likelihood ratio for a positive test result (LR+) was 2.7 in the distinction between pneumococcal and viral CAP and 3.9 between atypical and viral CAP. If there was a higher value in one of these four parameters (CRP > 200 mg/L, WBC count > 22 x 10(9)/L, PCT > 18 ng/mL or ESR > 90 mm/h) LR+ changed to >or=3.4, which means a significant increase from pre-test to post-test disease probability. An alveolar radiological infiltration was associated with higher values in non-specific inflammatory markers when compared with interstitial infiltrates, but there were no significant associations between radiological and etiological findings.

CRP, WBC count, PCT and ESR or their combinations have a limited role in screening between bacterial and viral pediatric CAP. If all or most of these markers are elevated, bacterial etiology is highly probable, but low values do not rule out bacterial etiology.