Multivariable Cox proportional hazards models determined associations between prostasin level at enrolment and change in prostasin level over 6 months and respiratory death.<h4>Results</h4>Prostasin level at enrolment was higher in patients with IPF (n=624) <i>versus</i> controls (n=100) (fold-difference 1.75; p<0.001). The gene discussed is PRSS8; the disease is idiopathic pulmonary fibrosis.