KLK3 and COVID-19: For example, a prospective cohort study involving 91 patients with COVID-19 reported a considerably higher serum PSA level during the active COVID-19 infection phase (4.34 ± 3.78 ng/mL) compared to the pre-COVID-19 infection phase (1.58 ± 1.09 ng/mL; p < 0.001) and the post-COVID-19 infection phase (2.09 ± 2.70 ng/mL; p < 0.001).