SPP1 and infection: When comparing male and female patients, a significant increase in OPN level was observed in male patients with severe infection (21.14 ± 1.31) compared to non-severe counterparts (17.39 ± 0.57) (P = 0.014), as well as in female severe patients (23.56 ± 1.72) compared to non-severe female patients (17.33 ± 0.87) (P = 0.03) (Fig. 2.