However, others have used the rs2227631 genotype as a proxy for the 4G/5G locus, and found it to be the variant which was most highly associated with PAI-1 levels on GWAS analysis, suggesting that this may be the more important locus.[27] Third, the exposures of RSV/ bronchiolitis and LRI were based on a self-report questionnaire designed to elucidate infections resulting in lower respiratory symptoms in a child under the age of 2 years. This evidence concerns the gene SERPINE1 and infection.