Pearson analysis showed that APACHE-II score was positively correlated with PCT, 8-iso-PGF2α, and SP-D levels in children with severe pneumonia (r = 0.298, 0.376, 0.320, P < 0.05), CPIS score was positively correlated with PCT, 8-iso-PGF2α, and SP-D levels (r = 0.316, 0.422, 0.388, Fig. P < 0.05), PCIS score positively correlated with PCT, 8-iso-PGF2α, SP-D levels (r = 0.220, 0.312, 0.277, P < 0.05), as shown in Table 5. Here, SFTPD is linked to susceptibility to pneumonia measurement.