A further advantage was the strict criteria for selection meant that only those studies with the highest quality were included, and there was subsequently little bias or doubt of the validity of the data. However, with such stringent criteria set, some studies were excluded which may have been useful. This includes a number of studies which did not span 12 months. The reason for excluding such studies was to eliminate any seasonal variation. One excluded large multicentre multinational RCT  which enrolled over 600 children, given montelukast or placebo for 12 weeks, showed improvement in episode-free days, symptoms, use of OCS, β-agonist use and serum eosinophil counts. The population studied seemed to be >50% atopic and many suffered from daily symptoms, maybe more akin to the previous term of multiple-trigger wheeze. It is important, however, to note that this particular study was conducted by the pharmaceutical company marketing montelukast.