Predictive value of immune-related parameters in severe Mycoplasma pneumoniae pneumonia in children.

Background: The severity of Mycoplasma pneumoniae pneumonia (MPP) is strongly correlated with the extent of the host's immune-inflammatory response. In order to diagnose the severity of MPP early, this study sought to explore the predictive value of immune-related parameters in severe MPP (sMPP) in admitted children.

Methods: We performed a database analysis consisting of patients diagnosed at our medical centers with MPP between 2021 and 2023. We included pediatric patients and examined the association between complete blood cell count (CBC), lymphocyte subsets and the severity of MPP. Binary logistic regression was performed to identify the independent risk factors of sMPP. Receiver operating characteristic (ROC) curves were used to estimate discriminant ability.

Results: A total of 245 MPP patients were included in the study, with 131 males and 114 females, median aged 6.0 [interquartile range (IQR), 4.0-8.0] years, predominantly located in 2023, and accounted for 64.5%. Among them, 79 pediatric patients were diagnosed as sMPP. The parameters of CBC including white blood cell (WBC) counts, neutrophil counts, monocyte counts, platelet counts, and neutrophil-to-lymphocyte ratio (NLR), were higher in the sMPP group (all P<0.05). The parameters of lymphocyte subsets including CD3⁺ T cell ratio (CD3⁺%) and CD3⁺CD8⁺ T cell ratio (CD3⁺CD8⁺%), were lower in the sMPP group (all P<0.05). And CD3^-CD19⁺ B cell ratio (CD3^-CD19⁺%) was higher in the sMPP group. Logistic regression analysis showed that age, CD3^-CD19⁺%, and monocyte counts were identified as independent risk factors for the development of sMPP (all P<0.001). The three factors were applied in constructing a prediction model that was tested with 0.715 of the area under the ROC curve (AUC). The AUC of the prediction model for children aged ≤5 years was 0.823 and for children aged >5 years was 0.693.

Conclusions: The predictive model formulated by age, CD3^-CD19⁺%, and monocyte counts may play an important role in the early diagnosis of sMPP in admitted children, especially in children aged ≤5 years.