S100A8/A9 as a novel predictor for severe Mycoplasma pneumoniae pneumonia in children: A prospective observational study.

OBJECTIVE: The calprotectin S100A8/A9 complex is released by stimulating neutrophils and monocytes, and inducing cytokine secretion, modulating the inflammatory response. The aim of present study was to investigate the role of S100A8/A9 in Severe Mycoplasma Pneumoniae Pneumonia (SMPP). STUDY DESIGN: We conducted a prospective study on pediatric Mycoplasma Pneumoniae Pneumonia (MPP) from December 2023 to May 2024. Patients were categorized into the SMPP group and non-SMPP (Non-Mycoplasma Pneumoniae Pneumonia, NSMPP) group based on hospitalization. Matched subgroups were formed according to age, sex, co-infection. RESULTS: A total of 132 patients were included. Serum S100A8/A9 levels in SMPP were significantly higher than those in NSMPP group (5.877 [3.202, 9.257] vs. 4.349 [2.495, 6.902] μg/mL, p = 0.049). Both C-Reactive Protein (CRP) and Lactate Dehydrogenase (LDH) levels were significantly elevated in SMPP compared to NSMPP groups (p = 0.009 and p = 0.036, respectively). Multivariate logistic regression analysis revealed that S100A8/A9 levels is a key predictor for SMPP. The Area Under the ROC Curve (AUC) for S100A8/A9 levels in predicting SMPP was 0.601 (95% CI: 0.512‒0.685). Post-matching, the AUC increased to 0.714 (95% CI: 0.549‒0.845), with an optimal cutoff value of S100A8/A9 at 4.067 μg/mL, a sensitivity of 75%, and a specificity of 70%. Additionally, the AUCs for CRP and LDH were 0.701 and 0.690, respectively. The combined variables of S100A8/A9 and CRP achieved an AUC of 0.742 (95% CI: 0.580‒0.867), showing a relative advantage over S100A8/A9 alone. CONCLUSION: Our findings indicate that serum S100A8/A9 is a potential adjunct biomarker for predicting severe Mycoplasma Pneumoniae Pneumonia (SMPP) in children. The conclusion is preliminary exploration and requires further validation in larger, multicenter prospective cohorts.