Abstract: Objective  To explore blood routine, immunoglobulin, D-Dimer(DD) expression and their efficiency in predicting the risk of plastic bronchitis in children with refractory mycoplasma pneumoniae pneumonia(RMPP). 
Methods  A total of 125 children with RMPP(RMPP group) and 125 children with Mycoplasma pneumoniae pneumonia(MPP) (MPP group) in our hospital were selected. The blood routine ［white blood cell count(WBC), percentage of neutrophils(N%), percentage of lymphocytes(L%), platelet(PLT), lactate dehydro-genase(LDH), C-reactive protein(CRP), red blood cell distribution width(RDW), pre-albumin(PAB)］,serum immunoglobulin ［immunoglobulin(Ig) A, IgM, IgE, IgG］ and D-D level of children with or without plastic bronchitis were compared between the two groups and in RMPP group. The influencing factors of plastic bronchitis, the correlation between various indicators and the severity of plastic bronchitis ［pediatric risk of mortality Ⅲ(PRISM Ⅲ)］, and the efficiency of predicting plastic bronchitis were explored. 
Results  WBC, N%, LDH, CRP, IgM, IgE, and D-D in RMPP group were higher than those in MPP group, while L%, PLT, and PAB were lower than those in MPP group(P＜0.05). In the RMPP group, N%, LDH, CRP, IgM, IgE, and DD in children with plastic bronchitis were higher than those in children without plastic bronchitis, while L%, PLT, and PAB were lower than those in children without plastic bronchitis(P＜0.05). Multivariate Logistic regression analysis showed that an increase in IgM, IgE, N%, CRP, and D-D was a risk factor for plastic bronchitis(P＜0.05). Pearson analysis revealed that there was a positive correlation between N%, CRP, IgM, IgE, D-D and PRISMⅢ scorein children with plastic bronchitis(P＜0.05). The receiver operating characteristic(ROC)curve of N%, CRP, IgM, IgE, D-D to predict plastic bronchitis was drawn, and the area under the ROC curve(AUC) of IgM, IgE, N%, CRP, and D-D combined to predict plastic bronchitis was 0.896, which was greater than the AUC predicted by each index alone, with the best sensitivity of 84.21% and specificity of 85.85%. The AUC predicted by N%+CRP for type I plastic bronchitis was 0.867, which was greater than the AUC predicted by each index alone. The optimal sensitivity was 70.00% and the specificity was 88.89%. 
Conclusion  The expression of blood routine, immunoglobulin, and D-D in children with PMPP is obviously abnormal, and the combined detection of the three has a good effect in predicting the risk of plastic bronchitis. 

Key words: pneumonia, mycoplasma, immunoglobulins, D-dimer