SFTPD and pneumonia: PCT, 8-iso-PGF2α, and SP-D were compared between the pneumonia group and the control group at admission; PCT, 8-iso-PGF2α, SP-D, and Acute Physiology and Chronic Health Evaluation (APACHE-II), Pediatric Critical Illness Score (PCIS) and Clinical Pulmonary Infection Score (CPIS) scores were compared between children with severe pneumonia with different pathogen infection types and different prognostic outcomes; and the correlation between APACHE-II, CPIS, and PCIS scores and PCT, 8-iso-PGF2α, and SP-D levels was analysed in children with severe pneumonia.