Comparative Effectiveness of Multi Versus Single Intervention Allergen Reduction Strategies on Asthma Morbidity

Background and Significance: Asthma is a serious, complex, and highly prevalent childhood respiratory disorder leading to inflammation and narrowing of the airways. If uncontrolled it negatively impacts long-term lung function. An estimated 6.2 million, 1 in 12, U.S. children have asthma and asthma outcome disparities are pervasive. An important contributor to asthma disparities is greater exposure to asthma triggering allergens. The proposed study addresses an evidence gap related to the most effective way to reduce exposure to asthma triggers in the home.

Study Aims: There are three specific aims. First to compare the effectiveness of a multicomponent intervention to reduce asthma triggers to a single intervention to reduce cockroach exposure in the home testing the hypothesis that among children with asthma exposed to cockroaches, a single intervention targeting cockroach remediation is as effective one with multiple components that targets multiple allergens. Specific Aim 2 compares the effectiveness of the different interventions on the number of cockroaches in the home testing the hypothesis that insecticidal bait is as effective at reducing cockroaches as a multi-component approach. Specific Aim 3 examines whether the effect of insecticidal control on asthma outcomes differs by the allergen profile of the child. The investigators hypothesize that cockroach eradication results in improved outcomes independent of cockroach sensitization status and the number of other allergens to which a child is sensitized. The long term objective is to provide evidence for the NHLBI Expert Panel currently reviewing the Guidelines for the Diagnosis and Management of Asthma (EPR-3) and specifically the effectiveness of indoor allergen reduction strategies on asthma management.

Study Description: A 12-month, two group randomized clinical trial of 290 children ages 5 -17 with doctor diagnosed asthma recruited from clinics in the Greater New Orleans area. Comparator Group 1 targets dust mites, mold, cockroach, animal dander and smoke exposure. Interventions include asthma education, cleaning techniques, impermeable bed covers, HEPA vacuum cleaners, air purification, and insecticidal baiting. Comparator Group 2 targets cockroaches and the intervention is targeted insecticidal baiting.

Primary outcomes include asthma symptom days, asthma-related health care utilization (emergency room visits, hospitalization, unscheduled clinic visits), quality of life, asthma control, medication use, and cockroach burden. Pulmonary function will be measured as a secondary outcome. Asthma outcome data will be collected monthly. Other data will be collected during home visits at baseline, 3, 6, 9 and 12 months.

Each outcome will be modeled separately. Two sets of analyses will be conducted. First, a generalized linear regression model will be employed to model the change score from baseline to 12-months with Comparator group 2 as the predictor and other potential confounders as covariates. In the second approach, intervention effects will be assessed longitudinally by modelling the outcomes at each assessment time (excluding baseline) using models for repeated outcomes such as linear mixed model or generalized estimating equations depending on the distribution of the outcome. Sensitivity analyses will be performed to verify the stability of multiple imputation assumptions using different multiple imputation procedures and consistency of the final results.