Predictors Of Mycoplasma Pneumoniae Necrotizing Pneumonia In Children

Mycoplasma pneumoniae（MP）is one of the common pathogens of lower respiratory tract infections in children.It can occur throughout the year,mostly in winter and spring.Mycoplasma pneumoniae pneumonia（MPP）accounts for about10%-20%of community-acquired pneumonia（CAP）,and it is as high as 30%or more the during epidemic period.An epidemic occurs every 3-7 years.Respiratory droplets are the main vector.The incidence rate is highest in preschool and school age children.With a tendency of younger age in recent years^[1].Most children with MPP are mild and self-limiting.and there is no obvious sequelae after inflammation absorption.But a few patients may have complicated occlusive bronchitis,pleural effusion^[2],necrotizing pneumonia^[3],pneumothorax^[4]and other lung complication.Necrotizing pneumonia（NP）refers to the destruction of normal tissue structure of lung parenchyma caused by multiple pathogen infections in the lungs.Lung consolidation occurs in the early stage of the disease,and liquefaction necrosis occurs in the lung consolidation area.A plurality of thin-walled cavities or vesicles are formed,which can be merged into a large cavity^[5].About 3.7%of children with CAP have NP,and Streptococcus pneumoniae is the most common pathogen^[6,7].Necrotizing pneumonia is a rare and serious complication of Mycoplasma pneumoniae pneumonia.It is a serious condition and has a long course of disease.Some of them can be complicated by pneumothorax and bronchopleural fistula.A few serious cases are life-threatening,and the hospital stay is often longer.It not only harms the physical and mental health of children,but also greatly increases the financial burden of the family.In recent years,due to the improvement of NP knowledge and the application of CT by clinicians,there are more and more cases of Mycoplasma pneumoniae necrotizing pneumonia（MPNP）reported at home and abroad^[9-19],but the previous studies are mainly reported cases with small samples size.There are few studies on the risk factors for the development of MPNP in children.Differences of clinical features,laboratory results,imaging findings,and bronchoscopy between refractory Mycoplasma pneumoniae pneumonia（RMPP）and MPNP are needed to be further summarized,in order to provide a scientific basis for early diagnosis,treatment,and improvement of prognosis of MPNP.Objective1.Analyze the clinical manifestations,laboratory results,imaging findings and soft bronchoscopy of children with Mycoplasma pneumoniae necrotizing pneumonia（MPNP）.2.The clinical data of 40 patients with MPNP were compared with the clinical data of 60 patients with RMPP who had no lung necrosis during the same period.After statistical analysis,we try to find the early diagnosis indicators of MPNP.Methods1.100 children with clinical diagnosis of RMPP hospitalized from January 2014to December 2017 were enrolled in the Department of Pediatric Respiratory Medicine of our hospital.Among them,40 patients with pulmonary necrosis changed in the lung imaging group as necrotic group,and 60 patients with no pulmonary necrosis changed as non-necrotic group.Relevant clinical data were collected through detailed medical records,including gender,age,clinical manifestations,complications,laboratory tests,etc;laboratory indicators including white blood cell count（WBC）,neutrophil ratio,C-reactive protein（CRP）,D-dimer,lactate dehydrogenase（LDH）,etc.For the test items with multiple test results,the highest value was compared.After statistical analysis,the predicted index and critical value of MPNP were obtained.Data processing was performed using SPSS 21.0 statistical software.After univariate analysis,multivariate logistic regression analysis was performed on the statistically significant differences between the two groups.The predictive index of MPNP was obtained and the ROC curve was drawn.The difference was statistically significant at P<0.05.2.The study met the criteria of the hospital ethics committee,approved by the ethics committee,obtained the informed consent of the guardian,and signed a written consent.Results1.In 100 children with RMPP,40 patients with pulmonary necrosis were used as necrotic group,and 60 children with RMPP who had no necrotic changes in lung imaging were included as non-necrotic group.There was no significant difference in gender and age between the two groups（P>0.05）,which was comparable.2.Compare the bronchoscopy changes between the necrotic group and the non-necrotic group.The results showed that inflammatory manifestations such as bronchial mucosal congestion and edema,white or yellow viscous secretions were observed in both groups.But there was no significant difference in the proportion of inflammatory stenosis,mucosal fold hyperplasia,sputum plug formation,and mucosal roughness under the microscope（P>0.05）.3.Compared with non-necrotic group,hospitalization time（d）（19.5?6.0 VS13.5?3.3,P<0.001）,fever time（d）（20.0?8.3 VS 12.0?3.6,P<0.001）,the proportion of liver damage（30%VS 3.3%,P<0.001）,ratio of pleural effusion（82.5%vs 53.3%,P=0.003）,peripheral blood leukocyte count（×10⁹/L）（16.2?5.5 VS11.0?3.2,P<0.001）,neutrophils Proportion（%）（79.8?7.0 VS 68.7?10.8,P<0.001）,C-reactive protein（mg/L）（117.4?60.4 VS 55.1?35.2,P<0.001）,D-dimer（mg/L）（5.26（3.07-8.32）VS 1.92（1.11-3.36）,P<0.001）,lactate dehydrogenase（U/L）（529.4?228.4 VS 426.2?152.7,P<0.001）,the children in the necrotic group were significantly higher than non-necrotic group.The difference between the two groups was statistically significant（P<0.05）.4.Multivariate logistic regression analysis was performed on the indicators with significant differences between the two groups.The results showed:WBC（OR=1.35,95%CI:1.09¹.68）,fever time（OR=1.22,95%CI:1.03¹.44）are risk factors for MPNP（P<0.05）.The ROC curves of WBC and fever time predicted MPNP were drawn.It was found that when WBC>12.6×10⁹/L and fever time>13.5d,there was a higher value for predicting MPNP（AUC=0.80,0.83,P<0.001）.Conclusions1.Compared with the non-necrotic group,the children in the necrotic group had longer fever time,the peripheral blood inflammation index was significantly increased,and the complications such as pleural effusion and liver injury were more easily combined.2.When the children with Mycoplasma pneumoniae lobar pneumonia have a fever time of>13.5 d,peripheral blood WBC>12.6×10⁹/L,and combined with liver damage,pleural effusion,we need to be vigilant that MPNP may occur.