SFTPD and susceptibility to pneumonia measurement: The results also showed that the expression levels of PCT, 8-iso-PGF2α and SP-D were higher in children with bacterial severe pneumonia and poor prognosis severe pneumonia, and APACHE-II, CPIS and PCIS scores were positively correlated with PCT, 8-iso-PGF2α and SP-D levels in children with severe pneumonia, indicating that the combined detection of PCT, 8-iso-PGF2α and SP-D could predict and evaluate the infection type, disease condition and prognosis quality of severe pneumonia, thus providing a reference basis for the disease evaluation and clinical treatment of severe pneumonia.