van Boven FE, et al. - Researchers focused on the effectiveness of air purification for the management of home-related allergic asthma (dust mite, dog, cat, and cockroach), to update the meta-analysis published by McDonald et al. [Chest 2002;122;1535–1542]. The trials studied by McDonald et al. as well as reports published since 2000 were analyzed for this purpose. They studied overall 10 trials with 482 patients. Among patients having mainly mild to moderate asthma at baseline, findings revealed statistically significant mean differences in the Asthma Quality of Life Questionnaire scores and fractional exhaled nitric oxide levels. The subgroup of patients receiving Global Initiative for Asthma step 4 therapy showed great improvement in a large trial.