Abstract: Objective　To investigate the differential diagnosis significance of serum procalcitonin（PCT）in children with bacterial and viral infected community-acquired pneumonia（CAP)，and compare the accuracies and application of C reactive protein（CRP)，erythrocyte sedimentation rate（ESR）and white blood cell（WBC）count.   Methods　A total of 79 patients with CAP（20 cases with lobar pneumonia and 59 cases with bronchopneumonia）and 21 healthy controls were enrolled. PCT，CRP，ESR and WBC count were determined. Receiver operating characteristic（ROC）curve analysis was performed. The 79 patients with CAP were classified into ＜2 years old group（31 patients)，2-5 years old group（18 patients）and ＞5 years old group（30 patients）according to their ages，and their PCT，CRP，ESR and WBC counts were compared. Results　Serurn PCT，CRP，ESR and WBC count were significanthy higher in CAP group than in control group（P＝0.000，P＜0.01). Serum PCT，CRP，ESR and WBC count in lobar oneumonia group were higher than those in bronchopneumonia group（P＜0.01). The level of PCT in ＞5 years old group were higher than that in ＜2 years old group（P＝0.000)，and the levels of CRP，ESR and WBC count had no statistical significance among the different age groups（P＞0.05). The area under receiver sperating chara cteristic（ROC）curve of PCT was 0.97 [95% confidence inter val （CI）：0.93-1.00]，which was higher than those of CRP [0.91（95%CI：0.78-0.99)] and ESR [0.87（95% CI:0.78-0.96)]（P＜0.01). The area of WBC count [0.95（0.95%CI：0.91-0.98)] had no statistical significance（P＝0.14). The best cut-off value of PCT was 1 ng/mL，and the sensitivity and specificity were 94.1% and 82.3%. Conclusions　Serum PCT level is a better marker than CRP and ESR for the diagnosis of CAP in children，and can be used as a reliable indicator of the early diagnosis for clinicians and rational use of antibiotics.

Key words: Procalcitonin, Childhood community-acquired pneumonia, C reactive protein, Erythrocyte sedimentation rate, White blood cell count