The investigators therefore performed a proof-of-concept randomized controlled trial to determine whether genetically susceptible children with homozygous Arg16 genotype experience superior long-term asthma control with montelukast compared with salmeterol when used as tailored second-line controller therapy as add-on to the inhaled steroid fluticasone. The purpose of this preliminary study was to provide evidence to support the potential for personalised medicine based on the individual genotype to improve asthma-related quality-of-life and control. This study was published in 2013, and represents the first prospective randomized controlled study in children with asthma that addresses personalised medicine based on genotype. The results of this study showed that in children expressing the homozygous Arg 16 genotype, in comparison with salmeterol, adding montelukast to inhaled fluticasone significantly improved asthma-related quality-of-life and clinical symptoms, while reducing school absences and inhaled reliever use. The relative benefits of montelukast in comparison with salmeterol became evident within the first 3 months and persisted throughout the whole year.