Study of Indoor Allergen Reduction for Asthma Management: How Will this Impact Future Guidelines?

The National Asthma Education and Prevention Program was established in 1989 to address increasing asthma mortality and morbidity. The group recommends that the National Heart, Lung, and Blood Institute (NHLBI) partner with medical societies to create clinical guidelines. Recently, NHLBI formed a working group to consider updates to the latest Expert Panel Report, and identified the following topics for review:

• Clinical utility of fractional exhaled nitric oxide in asthma management
• Immunotherapy in treatment of asthma
• Intermittent inhaled corticosteroids and long-acting muscarinic antagonists for asthma
• Effectiveness and safety of bronchial thermoplasty management of asthma
• Effectiveness of indoor allergen reduction in management of asthma

The University of Pennsylvania (UPenn) was contracted to take on the last topic. During a session at the 2018 AAAAI Annual Meeting, Andrea J. Apter, MD, MA, MSc, and Brian F. Leas, MS, MA, both of UPenn, discussed this research project.

“We conducted a systematic review to help the panel writing that guideline,” Dr. Leas said, noting that they are not sure of its status and do not know what the panel’s ultimate recommendations will be. “But it’s important to discuss what we found and how we interpreted the findings,” he said.

Their review focused on six allergens: animal dander, cockroaches, house dust mites, household pets, mold, and rodents; other allergen and irritants were excluded. They examined eight interventions: acaricide, air purification, carpet removal, carpet cleaning, pillow and mattress covers, mold removal, pest control, and pet removal, with articles focusing on both single- and multi-component interventions.

The study population included both adults and children; ≥85% had an asthma diagnosis, any disease severity was allowed, and they looked at home-, school-, and work-related allergens. Case series and reports, as well as risk-association studies were excluded, and they only used interventional studies. “We looked for best available research,” Dr. Leas said of their parameters.

The primary outcomes of the included studies were validated measures of control, asthma exacerbations, asthma-related healthcare utilization and costs, pulmonary physiology, and quality of life. A secondary outcome was allergen reduction.

They narrowed the study pool to 59 randomized, controlled trials (RCTs) and eight observational studies. The researchers focused more on the RCTs when analyzing outcomes: 25 were multi-component studies, 17 studies looked at single intervention mattress covers, and nine looked at single intervention air purifiers. The studies were diverse in terms of age cohorts and were conducted worldwide. Dr. Leas noted that the NHLBI will need to consider how relevant some of these studies are when writing the guidance, however.

Identifying statistically significant interventions and combinations of interventions was difficult, Dr. Leas said. “We can’t say, ‘These two things are always included in [positive] studies,’” he noted. They did find statistically significant improvements mostly in the areas of symptom and allergen reductions, but it is unknown if these were clinically significant.

Dr. Apter discussed highlights of the findings, including:

• Single interventions were not generally associated with improvement in asthma measures
• Multi-component interventions improved various outcomes, but no combination of specific interventions appeared to be more effective than another
• No high strength evidence suggests improvement in any of the primary outcomes
• Evidence was often inconclusive due to lack of studies
• Validated measures of asthma control were infrequently reported
• Other standardized measure, such as exacerbations, healthcare utilization, and quality of life, were infrequently reported.

“This is a roadmap to what the next steps may be to develop more useful guidelines moving forward,” Dr. Leas concluded.

Drs. Apter and Leas noted some limitations of their work, including a high degree of heterogeneity and variation in asthma severity among studies; home-based interventions are difficult to implement for various reasons, including cost, language, technology, home ownership, and health literacy; adherence to protocols is difficult; and attrition rates were high in some studies.

The ultimate goal is to establish a guideline that will improve asthma outcomes, Dr. Apter said.

Presentation 3705: HEDQ: Asthma Guidelines for Indoor Allergen Interventions: Methods and Clinical Implications