ARTI is the most common infectious disease in children, and has a significant impact on children's health. The diagnosis and differential diagnosis of infection types need the support of bacterial culture and serological diagnosis. The process is time-consuming and tedious, and the results can not be fed back to the clinic in time. Experiential medication is a common clinical treatment, and it is also one of the causes of antimicrobial drug abuse and bacterial resistance. It is an urgent problem to quickly distinguish the types of infection and guide clinical accurate drug use. WBC count in blood routine is a common method in clinical diagnosis of infection. It is easy to operate and the result is fast. However, it is easy to be interfered by external factors, which affects the choice of clinical medication. Both PCT and CRP are acute phase reaction proteins, which can change according to the level of inflammatory factors. The level of PCT in serum increases significantly, when the body is infected with pathogens. The degree of increase is related to the degree of infection[13–14]. CRP is a non-specific acute phase reaction protein synthesized by hepatocytes. As an inflammatory marker, it is easy to detect and has high accuracy. It is widely used in the diagnosis of acute infection and the prognosis of patients[15–16]. Therefore, on the basis of bacterial culture and serological identification, combined with other inflammatory factors, it is expected to quickly distinguish the types of acute respiratory infection, and provide meaningful data for clinical reference.
The results of this study show that the levels of PCT, CRP and WBC in group A were significantly higher than those in group B and group C(P < 0.05). It's clear that bacterial infections can lead to elevated levels of above indicators. It is consistent with the relevant research results [17–18]. This may be related to the failure of PCT to break down into calcitonin under the action of cytokines during bacterial infection, resulting in the increase of PCT level in blood. There was no significant difference in the levels of PCT, CRP and WBC between group B and group C (P > 0.05). And these are similar to the normal value. It further suggests the value in the differential diagnosis of bacterial infection. When PCT, CRP or WBC remarkably increased, the possibility of bacterial infection increased significantly. It can guide the clinical early use of broad-spectrum cephalosporins or aminoglycoside antibiotics for treatment, and can achieve ideal therapeutic effect. Then the positive rates of PCT, CRP and WBC among the three groups were compared. The positive rates of PCT and CRP in group A were significantly higher than those in group B and group C (P < 0.05). This result is consistent with the above. There was no significant difference in the positive rate of WBC among the three groups (P > 0.05). More importantly, the combined diagnosis of three indicators can significantly improve the positive rate of diagnosis. In agreement with the findings of the present study, a large number of studies showed that combined detection is conducive to the diagnosis of the disease[20–21]. This suggests that clinical multi-index joint detection is very important for the diagnosis of disease.
To further analyze the diagnostic efficacy of PCT, CRP and WBC using ROC curve for bacterial ARTI. The result showed that the AUC of PCT, CRP and WBC were 0.65, 0.55 and 0.58 respectively. The sensitivity and AUC of PCT were higher than those of CRP and WBC. It suggested that the diagnostic value of PCT and CRP was better than that of WBC in bacterial infection, and WBC is not useful at all. It was consistent with the relevant research studies[22–23]. Because the preferred antibiotics for different bacterial infections are not the same, single broad-spectrum antibiotic treatment is difficult to continuously control the development of the disease, so it is necessary to further explore the types of bacterial infections. Among 108 children with bacterial ARTI, there were 60 cases of G+ bacteria and 48 cases of G− bacteria.. As shown in Table 4, G+ bacteria were mainly Streptococcus pneumoniae and Staphylococcus aureus, G− bacteria were mainly Escherichia coli and Haemophilus influenzae. As we all know, these bacteria are common pathogens of respiratory tract. Children are very vulnerable to infection due to their poor development and low immunity. Next, the levels and diagnostic positive rate of PCT, CRP and WBC between G+ and G− bacterial infection group were depth comparative analyzed. As shown in Table 5, the overall levels of G− bacterial group are slightly higher than that of G+ bacterial group. However, there were no significant differences in PCT, CRP, WBC levels and diagnostic positive rates between G+ and G− bacterial infection groups (P > 0.05). This result is a little different from that of Tang et al , which may be due to insufficient cases included in this study. In the follow-up work, more cases will be considered in order to get more accurate results for clinic.