3.2 Radiological and laboratory findings
The chest CT results of all involved children were obtained on admission, and 130 (71.4%) had abnormal images, of which 57 (43.8%) appeared in both lungs, and the rest (56.2%) in unilateral lung. The common signs of pneumonia in chest CT scans were ground-glass opacities (GGO) and local patchy shadowing (Figure 2), with the incidence of 28.0% and 27.5%, respectively, whereas the pulmonary consolidation was much less (1.6%). It was worth noting that there were also 52 (28.6%) infected children without any changes in chest CT images. Thus, the concurrence of normal chest CT scan and no symptom contributed to 24 cases of asymptomatic infection, in the ratio of 13.2% (Table 1).
The median values of laboratory results were mostly within normal ranges, and the details were listed in Table 3 and 4. The rates of decreased count and percentage of lymphocytes were 3.9% and 34.6%, respectively; those of eosinophils were 29.5% and 18.8%, respectively. Other findings in differential of white blood cells included increased and decreased neutrophil percentage (27.4% and 24.0%), and increased monocyte percentage (33.3%). Although the levels of PCT and CK-MB elevated in almost the half (both 47.5%), they changed slightly and had no clinical significance. The majority (33/39, 84.6%) of identified possible co-infected pathogen was mycoplasma pneumoniae (MP), and the other tested pathogens were much less identified. With a further analysis of the subgroup of possible co-infection with MP, GGO in chest CT images was less found (21.1% vs 31.5%, p = 0.025), azithromycin was more used (12.1% vs 1.3%, p = 0.01), and decreased monocytes count was more common (26.1% vs 5.2%, p = 0.005). Possible MP co-infection had no influence on serum levels of inflammatory indicators, such as CRP, PCT and D-dimer. In addition, there was no difference in the prevalence of allergic diseases between children possibly co-infected with MP or not (Table S1 and S2).