Serum SP-A levels were significantly higher in patients with IPF than in patients with non-IPF ILD (SMD: 1.108 [0.584, 1.632], P < .001), or pulmonary infection (SMD: 1.320 [0.999, 1.640], P < .001) and healthy controls (SMD: 2.802 [1.901, 3.702], P < .001).
Single-nucleotide polymorphisms (SNPs) in SP-A1 and SP-A2, genes encoding SP-A, have been associated with susceptibility to respiratory distress syndrome, COPD, and pulmonary infections.