Exacerbations in Adults with Asthma: A Systematic Review and External Validation of Prediction Models.

BACKGROUND: Several prediction models assessing future risk of exacerbations in adult patients with asthma have been published. Applicability of these models is uncertain because their predictive performance has often not been assessed beyond the population in which they were derived. OBJECTIVE: This study aimed to identify and critically appraise prediction models for asthma exacerbations and validate them in 2 clinically distinct populations. METHODS: PubMed and EMBASE were searched to April 2017 for reports describing adult asthma populations in which multivariable models were constructed to predict exacerbations during any time frame. After critical appraisal, the models' predictive performances were assessed in a primary and a secondary care population for author-defined exacerbations and for American Thoracic Society/European Respiratory Society-defined severe exacerbations. RESULTS: We found 12 reports from which 24 prediction models were evaluated. Three predictors (previous health care utilization, symptoms, and spirometry values) were retained in most models. Assessment was hampered by suboptimal methodology and reporting, and by differences in exacerbation outcomes. Discrimination (area under the receiver-operating characteristic curve [c-statistic]) of models for author-defined exacerbations was better in the primary care population (mean, 0.71) than in the secondary care population (mean, 0.60) and similar (0.65 and 0.62, respectively) for American Thoracic Society/European Respiratory Society-defined severe exacerbations. Model calibration was generally poor, but consistent between the 2 populations. CONCLUSIONS: The preservation of 3 predictors in models derived from variable populations and the fairly consistent predictive properties of most models in 2 distinct validation populations suggest the feasibility of a generalizable model predicting severe exacerbations. Nevertheless, improvement of the models is warranted because predictive performances are below the desired level.

Identifying patients at risk for severe exacerbations of asthma: development and external validation of a multivariable prediction model.

BACKGROUND: Preventing exacerbations of asthma is a major goal in current guidelines. We aimed to develop a prediction model enabling practitioners to identify patients at risk of severe exacerbations who could potentially benefit from a change in management. METHODS: We used data from a 12-month primary care pragmatic trial; candidate predictors were identified from GINA 2014 and selected with a multivariable bootstrapping procedure. Three models were constructed, based on: (1) history, (2) history+spirometry and (3) history+spirometry+FeNO. Final models were corrected for overoptimism by shrinking the regression coefficients; predictive performance was assessed by the area under the receiver operating characteristic curve (AUROC) and Hosmer-Lemeshow test. Models were externally validated in a data set including patients with severe asthma (Unbiased BIOmarkers in PREDiction of respiratory disease outcomes). RESULTS: 80/611 (13.1%) participants experienced ≥1 severe exacerbation. Five predictors (Asthma Control Questionnaire score, current smoking, chronic sinusitis, previous hospital admission for asthma and ≥1 severe exacerbation in the previous year) were retained in the history model (AUROC 0.77 (95% CI 0.75 to 0.80); Hosmer-Lemeshow p value 0.35). Adding spirometry and FeNO subsequently improved discrimination slightly (AUROC 0.79 (95% CI 0.77 to 0.81) and 0.80 (95% CI 0.78 to 0.81), respectively). External validation yielded AUROCs of 0.69 (95% CI 0.63 to 0.75; 0.63 to 0.75 and 0.63 to 0.75) for the three models, respectively; calibration was best for the spirometry ­model. CONCLUSIONS: A simple history-based model extended with spirometry identifies patients who are prone to asthma exacerbations. The additional value of FeNO is modest. These models merit an implementation study in clinical practice to assess their utility. TRIAL REGISTRATION NUMBER: NTR 1756.

Comparative effectiveness of long term drug treatment strategies to prevent asthma exacerbations: network meta-analysis.

OBJECTIVE: To determine the comparative effectiveness and safety of current maintenance strategies in preventing exacerbations of asthma. DESIGN: Systematic review and network meta-analysis using Bayesian statistics. DATA SOURCES: Cochrane systematic reviews on chronic asthma, complemented by an updated search when appropriate. ELIGIBILITY CRITERIA TRIALS OF Adults with asthma randomised to maintenance treatments of at least 24 weeks duration and that reported on asthma exacerbations in full text. Low dose inhaled corticosteroid treatment was the comparator strategy. The primary effectiveness outcome was the rate of severe exacerbations. The secondary outcome was the composite of moderate or severe exacerbations. The rate of withdrawal was analysed as a safety outcome. RESULTS: 64 trials with 59,622 patient years of follow-up comparing 15 strategies and placebo were included. For prevention of severe exacerbations, combined inhaled corticosteroids and long acting ß agonists as maintenance and reliever treatment and combined inhaled corticosteroids and long acting ß agonists in a fixed daily dose performed equally well and were ranked first for effectiveness. The rate ratios compared with low dose inhaled corticosteroids were 0.44 (95% credible interval 0.29 to 0.66) and 0.51 (0.35 to 0.77), respectively. Other combined strategies were not superior to inhaled corticosteroids and all single drug treatments were inferior to single low dose inhaled corticosteroids. Safety was best for conventional best (guideline based) practice and combined maintenance and reliever therapy. CONCLUSIONS: Strategies with combined inhaled corticosteroids and long acting ß agonists are most effective and safe in preventing severe exacerbations of asthma, although some heterogeneity was observed in this network meta-analysis of full text reports.

Asthma control cost-utility randomized trial evaluation (ACCURATE): the goals of asthma treatment.

BACKGROUND: Despite the availability of effective therapies, asthma remains a source of significant morbidity and use of health care resources. The central research question of the ACCURATE trial is whether maximal doses of (combination) therapy should be used for long periods in an attempt to achieve complete control of all features of asthma. An additional question is whether patients and society value the potential incremental benefit, if any, sufficiently to concur with such a treatment approach. We assessed patient preferences and cost-effectiveness of three treatment strategies aimed at achieving different levels of clinical control:1. sufficiently controlled asthma2. strictly controlled asthma3. strictly controlled asthma based on exhaled nitric oxide as an additional disease marker DESIGN: 720 Patients with mild to moderate persistent asthma from general practices with a practice nurse, age 18-50 yr, daily treatment with inhaled corticosteroids (more then 3 months usage of inhaled corticosteroids in the previous year), will be identified via patient registries of general practices in the Leiden, Nijmegen, and Amsterdam areas in The Netherlands. The design is a 12-month cluster-randomised parallel trial with 40 general practices in each of the three arms. The patients will visit the general practice at baseline, 3, 6, 9, and 12 months. At each planned and unplanned visit to the general practice treatment will be adjusted with support of an internet-based asthma monitoring system supervised by a central coordinating specialist nurse. Patient preferences and utilities will be assessed by questionnaire and interview. Data on asthma control, treatment step, adherence to treatment, utilities and costs will be obtained every 3 months and at each unplanned visit. Differences in societal costs (medication, other (health) care and productivity) will be compared to differences in the number of limited activity days and in quality adjusted life years (Dutch EQ5D, SF6D, e-TTO, VAS). This is the first study to assess patient preferences and cost-effectiveness of asthma treatment strategies driven by different target levels of asthma control. TRIAL REGISTRATION: Netherlands Trial Register (NTR): NTR1756.

Definitions of asthma exacerbations.

PURPOSE OF REVIEW: During the past decade exacerbations of asthma have increasingly been recognized a as primary outcome parameter in clinical research. However, comparison of results is hampered by the use of different definitions for asthma exacerbations in published reports. The purpose of this review is to describe the consequences of using different definitions and to propose possible solutions. RECENT FINDINGS: The use of different definitions of asthma exacerbations not only influences incidence rates, but also affects patient identification and risk assessment. The American Thoracic Society/European Respiratory Society and the World Health Organization independently proposed consensus definitions based on clinical symptoms and management. This needs to be complemented by a prospective definition that may support clinicians in their treatment decisions. CONCLUSION: Currently there is no commonly accepted definition for asthma exacerbations. A prospective definition is desirable. This could be obtained by phenotyping asthma exacerbations based on clinical signs, lung function parameters and possibly other biomarkers.