Supplementary file 1_S100A8/A9 as a biomarker for differentiating pulmonary tuberculosis from community-acquired pneumonia in children: a multicenter cohort study in China.docx

For distinguishing PTB from CAP, S100A8/A9 achieved AUC values of 0.916 (95% CI: 0.895-0.937, sensitivity 87.1%, specificity 81.8%) in the discovery cohort and 0.932 (95% CI: 0.906–0.958, sensitivity 87.5%, specificity 86.4%) in the validation cohort. Compared with all CAP etiological subgroups, PTB children had the lowest S100A8/A9 levels, with the highest AUC of 0.954 for PTB vs. Mycoplasma pneumoniae CAP. Age-stratified analysis revealed excellent discriminatory performance in children aged 5-18 years (AUC = 0.955 for PTB versus overall CAP). but impaired in children under 5 years (AUC = 0.838 for PTB versus overall CAP), with lower sensitivity (57.4%) for discriminating PTB from Viral-CAP.

Furthermore, a concentration-dependent distribution was observed, with higher S100A8/A9 levels associated with a decreasing proportion of PTB and an increasing proportion of CAP. In children aged 5–18 years, levels < 1,000 ng/mL were predominantly PTB (92.1%), and levels > 1,900 ng/mL were highly predictive of CAP (96.8%).</p>Conclusions<p>Serum S100A8/A9 is a promising potential biomarker for distinguishing pediatric PTB from CAP, characterized by age-related distribution and concentration-dependent diagnostic pattern.</p>