We did a prespecified analysis of the ADRB@ polymorphisms Arg@Gly and Gln@Glu within the @ year randomised , double-blind , double-dummy , parallel-group Prevention Of Exacerbations with Tiotropium in COPD ( POET-COPD ) trial , comparing the effects of treatment with tiotropium or salmeterol on exacerbations in @ patients with COPD .