SFTPD and pulmonary fibrosis: However, a different study found the mean value of SP-D to be 88 ng/mL ( range 1–1354 ng/mL) in patients with lung injury.[15] In healthy adults and children the average level of SP-D is approximately 60 ng/mL.[10] Increased levels of SP-D have been reported in idiopathic pulmonary fibrosis (IFP), tuberculosis, pulmonary alveolar proteinosis, andlues vave ranger between 100 ng/mL (sarcoidosis) to 339 ng/mL (IPF) compared to a control group of healthy patients (66ng/mL).