SPP1 and asthma: The serum levels of OPN were significantly higher in subjects with asthma than in HCs (3.41 ± 0.54 vs. 2.99 ± 0.83 pg/mL) (Fig. 1a) and in patients with LOA compared to those with EOA (3.57 ± 0.41 vs. 3.31 ± 0.59 pg/mL) (Fig. 1b and Table 1).