Subsequently, the investigators systematically searched for other randomised controlled trials comparing the effects of salmeterol (or other long-acting beta2 agonist) with montelukast (or other leukotriene antagonist) within the context of Arg/Gly variation, in children with asthma. No studies could be identified. In particular, there were no trials in either adults or children that have studied quality-of-life, which is a key outcome of interest in the context of asthma-related disability, and which is often unrelated to outcomes such as lung function. The absence of other randomised trials, together with the strength of the investigators proof-of-concept evidence, underscores the need for this powered study.