SFTPD and acute respiratory distress syndrome: Median SP-D level in plasma was 20.8 ng/mL [(IQR, 13.2–38.4); mean 27.0 ± 19.9 ng/mL] in cases with direct ARDS and 16.3 ng/mL [(IQR, 9.7–38.3); mean 24.3 ± 18.4 ng/mL] in cases with indirect ARDS.