Temperature-controlled Laminar Airflow (TLA) in symptomatic severe asthma - a post hoc analysis of severe exacerbations, quality of life and health economics.

PURPOSE: Uncontrolled severe asthma constitutes a major economic burden to society. Add-ons to standard inhaled treatments include inexpensive oral corticosteroids and expensive biologics. Nocturnal treatment with Temperature-controlled Laminar Airflow (TLA; Airsonett®) could be an effective, safe and cheaper alternative. The potential of TLA in reducing severe asthma exacerbations was addressed in a recent randomised placebo-controlled trial (RCT) in patients with severe asthma (Global Initiative for Asthma (GINA) step 4/5), but the results were inconclusive. We re-analysed the RCT with severe exacerbations stratified by the level of baseline asthma symptoms and Quality of Life. METHODS: More uncontrolled patients, defined by Asthma Control Questionnaire 7 (ACQ7) > 3, EuroQoL 5-Dimension Questionnaire Visual Analogue Scale (EQ5D-VAS) ≤ 65 and Asthma Quality of Life Questionnaire (AQLQ) ≤ 4 were selected for re-analysis. The rates of severe asthma exacerbations, changes in QoL and health-economics were analysed and compared between TLA and placebo. RESULTS: The study population included 226 patients (113 TLA / 113 placebo.) The rates of severe asthma exacerbations were reduced by 33, 31 and 25% (p = 0.083, 0.073, 0.180) for TLA compared to placebo, dependent on selected control measures (ACQ7, EQ5D-VAS, AQLQ, respectively). For patients with less control defined by AQLQ≤4, the difference in mean AQLQ0-12M between TLA and placebo was 0.31, 0.33, 0.26 (p = 0.085, 0.034, 0.150), dependent on selected covariate (AQLQ, EQ5D-VAS, ACQ7, respectively). For patients with poor control defined by ACQ7 > 3, the difference in EQ5D-5 L utility scores between TLA and placebo was significant at 9 and 12 months with a cost-effective ICER. The results from the original study did not demonstrate these differences. CONCLUSION: This post hoc analysis demonstrated an effect of TLA over placebo on severe exacerbations, asthma control and health economics in a subgroup of patients with more symptomatic severe allergic asthma. The results are consistent with the present recommendations for TLA. However, these differences were not demonstrated in the full study. Several explanations for the different outcomes have been outlined, which should be addressed in future studies. FUNDING: NIHR Health Technology Assessment Programme and Portsmouth Hospitals NHS Trust.

Effect of nocturnal Temperature-controlled Laminar Airflow on the reduction of severe exacerbations in patients with severe allergic asthma: a meta-analysis.

Background: Allergen avoidance is important in allergic asthma management. Nocturnal treatment with Temperature-controlled Laminar Airflow (TLA) has been shown to provide a significant reduction in the exposure to allergens in the breathing zone, leading to a long-term reduction in airway inflammation and improvement in Quality of life (QoL). Allergic asthma patients symptomatic on Global Initiative for Asthma (GINA) step 4/5 were found to benefit the most as measured by Asthma Quality of Life Questionnaire (AQLQ). However, the effect of TLA on severe asthma exacerbations is uncertain and therefore a meta-analysis was performed. Methods: Patients with severe allergic asthma (GINA 4/5) were extracted from two 1-year randomised, double-blind, placebo-controlled trials conducted with TLA. A meta-analysis of the effect on severe exacerbations was performed by negative binomial regression in a sequential manner, defined by baseline markers of asthma control (symptoms and QoL scores). Results: The pooled dataset included 364patients. Patients with more symptoms at baseline (ACT<18 or ACQ7>3; N=179), had a significant mean 41% reduction in severe exacerbations (RR=0.59 (0.38-0.90); p=0.015) in favour of TLA. Higher ACQ7 cut-points of 3.5-4.5 resulted in significant reductions of 48-59%.More uncontrolled patients based on AQLQ total and symptom domains ≤3.0 at baseline also showed a significant reduction in severe exacerbations for TLA vs. placebo ((47% (p=0.037) and 53% (p=0.011), respectively). The meta-analysis also confirmed a significant difference in AQLQ-responders ((Minimal Clinically Important Difference)≥0.5; 74% vs. 43%, p=0.04). Conclusion: This meta-analysis of individual patient data shows a beneficial effect on severe exacerbations and quality of life for TLA over placebo in more symptomatic patients with severe allergic asthma. These outcomes support the national management recommendations for patients with symptomatic severe allergic asthma. The actual effect of TLA on severe exacerbations should be confirmed in a prospective study with larger numbers of patients.