Introduction: Interstitial lung diseases (ILDs) are a heterogeneous group of disorders. Serum biomarkers have sparked rising interest regarding ILDs diagnosis and prognosis. 
Objective: To evaluate the utility of the serologic levels of osteopontin (OPNs), as well as OPN genetic polymorphisms as prognostic and diagnostic biomarker in ILDs.
Methods: Prospective, observational, single-center study. 344 ILD cases and 140 healthy volunteers  were recruited. ILD subtype diagnosis, time to death or transplantation, or pulmonary function severity was correlated with OPNs. Six genetic polymorphisms within SPP1 (rs28357094, rs2853749, rs2853750, rs11728697, rs7695531, rs1126616) were genotyped by TaqMan assays

Results: OPNs was higher in ILD patients than in controls (1141 (787 - 1690) pg/ml vs. 805 (648 - 980) pg/ml; p<?0.001). We found no differences in OPNs among different ILD groups. OPNs was correlated with forced vital capacity (SŽs rho -0.132, p=0.039) and with the FVC variation in the 12 months before baseline  (SŽs rho -0.228, p= 0.006). OPNs was higher in patients whose FVC declined>10% in the year before or after baseline (p<0.05). Survival was lower in patients with OPNs higher than a cut-off level of 1031 pg/ml (Figure 1). No differences in the genotype frequencies between the different subtype of ILDs were observed when each genetic polymorphism of SPP1 was analyzed independently.
Conclussion: OPNs could be useful as a biomarker assessing ILD severity.