Furthermore, our research findings imply that, neither platelet 5-HT concentration nor platelet MAO-B activity helps establish asthma severity or differentiate asthma phenotypes (i.e., allergic versus non-allergic asthma, T2-high versus T2-low asthma, non-eosinophilic versus eosinophilic asthma, or non-AERD versus AERD). This evidence concerns the gene MAOB and asthma.