Design and analytic considerations in determining the cost-effectiveness of early intervention in asthma from a multinational clinical trial

[Economic analysis of multinational clinical trials in oncology]

In oncology, as in other fields of medicine, international multicentre clinical trials came into being so as to include a sufficient number of subjects to investigate a clinical situation. The existence of tight budgetary constraints and the desire to make the best use of the resources available have resulted in the development of economic evaluations associated with these trials, which, thanks to their level of evidence and their size, provide particularly relevant material. Nonetheless, economic evaluations alongside international clinical trials raise specific questions of methodology with regard to both the design and the analysis of the results. Indeed, the costs of goods and services consumed, the types and quantities of resources, and medical practices vary from one country to another and within an individual country. Economic data from the different countries involved must be available so as to study and to take into account this variability, and appropriate techniques for cost estimations and analysis must be implemented to aggregate the results from several countries. From a review of the literature, the aim of this work was to provide an overview of the specific methodological features of economic evaluations alongside international clinical trials: analysis of efficacy data from several countries, collection of resources and real costs, methods to establish the monetary value of resources, methods to aggregate results accounting for the trial effect.

A patient advocate to facilitate access and improve communication, care, and outcomes in adults with moderate or severe asthma: Rationale, design, and methods of a randomized controlled trial

Few interventions to improve asthma outcomes have targeted low-income minority adults. Even fewer have focused on the real-world practice where care is delivered. We adapted a patient navigator, here called a Patient Advocate (PA), a term preferred by patients, to facilitate and maintain access to chronic care for adults with moderate or severe asthma and prevalent co-morbidities recruited from clinics serving low-income urban neighborhoods. We describe the planning, design, methodology (informed by patient and provider focus groups), baseline results, and challenges of an ongoing randomized controlled trial of 312 adults of a PA intervention implemented in a variety of practices. The PA coaches, models, and assists participants with preparations for a visit with the asthma clinician; attends the visit with permission of participant and provider; and confirms participants' understanding of what transpired at the visit. The PA facilitates scheduling, obtaining insurance coverage, overcoming patients' unique social and administrative barriers to carrying out medical advice and transfer of information between providers and patients. PA activities are individualized, take account of comorbidities, and are generalizable to other chronic diseases. PAs are recent college graduates interested in health-related careers, research experience, working with patients, and generally have the same race/ethnicity distribution as potential participants. We test whether the PA intervention, compared to usual care, is associated with improved and sustained asthma control and other asthma outcomes (prednisone bursts, ED visits, hospitalizations, quality of life, FEV1) relative to baseline. Mediators and moderators of the PA-asthma outcome relationship are examined along with the intervention's cost-effectiveness.

Cost-effectiveness analysis alongside clinical trials II-An ISPOR Good Research Practices Task Force report

Clinical trials evaluating medicines, medical devices, and procedures now commonly assess the economic value of these interventions. The growing number of prospective clinical/economic trials reflects both widespread interest in economic information for new technologies and the regulatory and reimbursement requirements of many countries that now consider evidence of economic value along with clinical efficacy. As decision makers increasingly demand evidence of economic value for health care interventions, conducting high-quality economic analyses alongside clinical studies is desirable because they broaden the scope of information available on a particular intervention, and can efficiently provide timely information with high internal and, when designed and analyzed properly, reasonable external validity. In 2005, ISPOR published the Good Research Practices for Cost-Effectiveness Analysis Alongside Clinical Trials: The ISPOR RCT-CEA Task Force report. ISPOR initiated an update of the report in 2014 to include the methodological developments over the last 9 years. This report provides updated recommendations reflecting advances in several areas related to trial design, selecting data elements, database design and management, analysis, and reporting of results. Task force members note that trials should be designed to evaluate effectiveness (rather than efficacy) when possible, should include clinical outcome measures, and should obtain health resource use and health state utilities directly from study subjects. Collection of economic data should be fully integrated into the study. An incremental analysis should be conducted with an intention-to-treat approach, complemented by relevant subgroup analyses. Uncertainty should be characterized. Articles should adhere to established standards for reporting results of cost-effectiveness analyses. Economic studies alongside trials are complementary to other evaluations (e.g., modeling studies) as information for decision makers who consider evidence of economic value along with clinical efficacy when making resource allocation decisions.

The development of a motivational interviewing intervention to promote medication adherence among inner-city, African-American adolescents with asthma

OBJECTIVE

to develop and assess the feasibility of a motivational interviewing (MI) based asthma self-management program for inner-city, African-American, adolescents with asthma.

METHODS

37 African-American adolescents (age 10-15 years) recently seen in an inner-city emergency department for asthma and prescribed an asthma controller medication participated in the newly developed program consisting of 5 home visits. Adolescents and their caregivers completed phone-based surveys before and after the intervention.

RESULTS

95% of the adolescents completed all 5 sessions; 89% of caregivers and 76% of adolescents believed other families would benefit from the intervention. Caregivers were more likely to report 100% adherence post-intervention compared to pre-intervention and reported a trend for adolescents taking greater responsibility for their asthma. There were no pre-post-differences in adolescent-reported medication adherence, but adolescents did reported increased motivation and readiness to adhere to treatment. Caregivers and adolescents each reported statistically significant increases in their asthma quality of life.

CONCLUSIONS

the findings from this pilot study suggest that MI is a feasible and promising approach for increasing medication adherence among inner-city adolescents with asthma and is worthy of further evaluation in a randomized trial.

PRACTICE IMPLICATIONS

incorporating MI into disease management programs may enhance their effectiveness.

Initial test of the seattle asthma severity and control questionnaire: a multidimensional assessment of asthma severity and control

BACKGROUND

The Seattle Asthma Severity and Control Questionnaire (SASCQ) was designed as a short, sensitive, and quantitative measure of asthma severity, impairment, and risk.

OBJECTIVES

To evaluate the distribution of responses to the SASCQ in a diverse asthma population and to determine whether the questionnaire is associated with other measures of asthma severity and control.

METHODS

A cross-sectional study of 188 asthmatic patients was conducted in a large academic primary care network. Asthma severity was confirmed in a subgroup of 44 patients by means of an in-person interview and lung function measurement.

RESULTS

The SASCQ score had a nearly normal distribution across the heterogeneous population and less of a floor effect than the number of asthma-free days. The SASCQ score showed a higher symptom burden in the mildest asthmatic patients compared with nonasthmatic controls. Asthma severity evaluated using the questionnaire was correlated with asthma severity evaluated by means of in-person interview and with controller medication class. The SASCQ score was associated with primary care visits for asthma, emergency department treatment for asthma, days missed from work, and confidence to control asthma symptoms; the associations between these measures of impairment and risk were all stronger for the SASCQ score than for asthma-free days.

CONCLUSIONS

The SASCQ is a quantitative measure of asthma that accurately discriminates between established levels of asthma severity and that is associated with other measures of asthma control and risk.

Transferability of economic evaluations: approaches and factors to consider when using results from one geographic area for another

BACKGROUND

Geographic transferability of economic evaluation data from one country to another has the potential to make a more efficient use of national and international evaluation resources. However, inappropriate transferability of economic data can provide misleading results and lead to an inefficient use of scarce health care resources.

OBJECTIVES

The objective of this study was to review, summarize and categorize the literature on: (i) factors affecting the geographic transferability of economic evaluation data; and (ii) approaches which have either been proposed or used for transferability.

METHODS

A systematic literature review on transferability was conducted. Electronic databases, hand searching and bibliographic searching techniques were utilized. Inclusion criteria for the review included conceptual or empirical papers with mention of factors affecting, or approaches for, transferability of economic evaluation data across geographic locations. Exclusion criteria included papers published prior to 1966, non-English language papers, pure science studies and animal studies. Three databases were involved in the primary search: Ovid MEDLINE, EMBASE, and CINAHL. In addition to the primary search, the Heath Economic Evaluation Database (OHE HEED), the NHS EED database and the EconLit databases were searched. Transferability factors were classified into major and minor categories, a classification of alternative transferability approaches was developed, and the number of empirical studies was catalogued according to this classification.

RESULTS

There is a substantial amount of literature on factors potentially affecting transferability. Based on these papers we identified 77 factors and subsequently developed a classification system which grouped these factors into five broad categories based on characteristics of the patient, the disease, the provider, the health care system and methodological conventions. Another 40 studies were identified which attempted to transfer economic evaluation data from one country to another and these were classified according to the sources for clinical efficacy, resource utilization and unit cost data.

CONCLUSIONS

There is strong evidence indicating that transferability of economic evaluation data is a difficult and complex task. Approaches which have been used for transferability suggest that, at a minimum, there is a need for country-specific substitution of practice pattern data as well as unit cost data. A limitation of this review relates to the lack of empirical studies which prevents stronger conclusions regarding which transferability factors are most important to consider and under which circumstances.

Cost-effectiveness of early intervention with once-daily budesonide in children with mild persistent asthma: results from the START study

The inhaled Steroid Treatment As Regular Therapy in early asthma (START) study has shown that early intervention with inhaled budesonide in mild persistent asthma improves clinical outcomes in both adults and children. The aim of this study was to estimate the incremental cost-effectiveness of early treatment with budesonide Turbuhaler in children aged 5-10 yr who participated in START. Direct and indirect costs associated with asthma were determined for 1974 children participating in the double-blind, 3-year part of the study. Randomization was to placebo or to budesonide 200 microg once daily in each case in addition to usual asthma care. Cost-effectiveness ratios were calculated from the healthcare payer's and societal perspectives (using US prices). The addition of once-daily budesonide therapy to usual asthma care was associated with 16 additional symptom-free days (SFDs) per child over the 3-yr period (p < 0.001), with a substantial reduction (50%) in the mean number of days spent in hospital, and with reduced frequency of emergency room visits and missed school and caregiver work days. From the healthcare payer's perspective (direct costs), the increase in mean direct cost over 3 yr with budesonide was 169 dollars, which translated into an incremental cost of early intervention with budesonide in children of 10.50 dollars (95% CI 1.20-33.30 dollars) per SFD gained. From the societal perspective, there was a cost reduction over 3 yr of 192 dollars with budesonide relative to placebo. From a societal perspective, budesonide was therefore dominant. In conclusion, early intervention with once-daily budesonide added to usual asthma care in children with mild persistent asthma is cost-saving from a societal perspective and is acceptably cost-effective when viewed from a healthcare payer perspective.

Good research practices for cost-effectiveness analysis alongside clinical trials: the ISPOR RCT-CEA Task Force report

OBJECTIVES

A growing number of prospective clinical trials include economic end points. Recognizing the variation in methodology and reporting of these studies, the International Society for Pharmacoeconomics and Outcomes Research (ISPOR) chartered the Task Force on Good Research Practices: Randomized Clinical Trials-Cost-Effectiveness Analysis. Its goal was to develop a guidance document for designing, conducting, and reporting cost-effectiveness analyses conducted as a part of clinical trials.

METHODS

Task force cochairs were selected by the ISPOR Board of Directors. Cochairs invited panel members to participate. Panel members included representatives from academia, the pharmaceutical industry, and health insurance plans. An outline and a draft report developed by the panel were presented at the 2004 International and European ISPOR meetings, respectively. The manuscript was then submitted to a reference group for review and comment.

RESULTS

The report addresses issues related to trial design, selecting data elements, database design and management, analysis, and reporting of results. Task force members agreed that trials should be designed to evaluate effectiveness (rather than efficacy), should include clinical outcome measures, and should obtain health resource use and health state utilities directly from study subjects. Collection of economic data should be fully integrated into the study. Analyses should be guided by an analysis plan and hypotheses. An incremental analysis should be conducted with an intention-to-treat approach. Uncertainty should be characterized. Manuscripts should adhere to established standards for reporting results of cost-effectiveness analyses.

CONCLUSIONS

Trial-based cost-effectiveness studies have appeal because of their high internal validity and timeliness. Improving the quality and uniformity of these studies will increase their value to decision makers who consider evidence of economic value along with clinical efficacy when making resource allocation decisions.

The effect of montelukast versus usual care on health care resource utilization in children aged 2 to 5 years with asthma

BACKGROUND

Limited clinical data are available on the long-term effects of asthma controller therapy on the utilization of health care resources in pediatric patients with asthma.

OBJECTIVE

The objective of this study was to compare the effects of long-term treatment with montelukast and usual care on health care resource use in children with asthma.

METHODS

Pediatric patients aged 2 to 5 years with asthma who had completed a 3-month, double-blind, double-dummy clinical trial comparing montelukast 4 mg and placebo were asked to participate in an open-label, controlled extension study comparing montelukast 4 mg and usual care. Usual care was defined as cromolyn or inhaled corticosteroid therapy Health care resource utilization was measured in terms of oral corticosteroid use and numbers of physician visits, emergency department visits, and hospitalizations.

RESULTS

Of 618 patients who completed the primary phase of the study, 516 (83.5%) participated in the extension study Data from 506 patients (302 without previous asthma maintenance therapy, 204 with) were included in the analysis. During the extension phase, patients who received montelukast and had not used previous asthma maintenance therapy were followed for a mean of 329.5 days; those who received usual care and

CONCLUSION

In this open-label study, pediatric patients aged 2 to 5 years with mild to moderate persistent asthma receiving long-term therapy with montelukast had similar rates of asthma-related health care resource utilization compared with those receiving usual care with cromolyn or inhaled corticosteroids.

Cost-effectiveness of formoterol and salbutamol as asthma reliever medication in Sweden and in Spain

This study aimed to evaluate the cost-effectiveness of formoterol (Oxis) Turbuhaler 4.5 microg and salbutamol 200 microg as reliever medications in Sweden and Spain. The study used data on effectiveness (exacerbations and symptom-free days) and resource utilisation from an open, 6-month, parallel-group, multicentre randomised trial with 18,124 asthma patients in 24 countries. Country-specific unit costs for Sweden and for Spain were used to transform resource utilisation data into costs. Total healthcare costs were not significantly different between formoterol and salbutamol dry powder inhalers in Sweden, whereas in Spain, the healthcare costs were 20% higher for formoterol vs. salbutamol pressurised metered dose inhalers. Total healthcare costs increased with disease severity, defined according to the Global Initiative for Asthma guidelines. Compared with salbutamol, formoterol produced statistically significant improvements in effectiveness, less reliever and maintenance medication usage, reduced healthcare resource utilisation, with no increase or a limited increase in healthcare cost.

An economic evaluation of combination treatment with budesonide and formoterol in patients with mild-to-moderate persistent asthma

Patients with mild asthma may benefit from increasing their inhaled corticosteroid dose, adding a long-acting beta2-agonist, or both. This study assessed the cost-effectiveness of these options. Patients aged > or = 12 years with mild-to-moderate persistent asthma (n = 1272) were randomised to twice-daily, double-blind treatment with budesonide 100 microg, budesonide 100 microg plus formoterol 4.5 microg, budesonide 200 microg, or budesonide 200 microg plus formoterol 4.5 microg for 12 months. Clinical variables included lung function, number of symptom-free days and number of severe exacerbations. Data on medication use, hospitalisation, visits to health professionals and time off work due to asthma were combined with Swedish unit cost data (1999) to estimate the mean annual cost per patient. Budesonide 200 microg plus formoterol 4.5 microg had the greatest efficacy and effectiveness. Budesonide 200 microg plus formoterol 4.5 microg was both more effective and less costly than budesonide 100 microg plus formoterol 4.5 microg, so a cost-effectiveness ratio was not calculated for this comparison. The cost-effectiveness ratio for budesonide 200 microg plus formoterol 4.5 microg compared with budesonide 200 microg alone was SEK 21 per symptom-free days gained. The combination of budesonide and formoterol in mild-to-moderate persistent asthma improved effectiveness at modest additional cost.

The impact of budesonide and other inhaled corticosteroid therapies in the management of asthma in children and adults

BACKGROUND

Since the recognition that asthma is characterized by extensive inflammation of the airways, the use of inhaled corticosteroids (ICSs) as controller therapy has become central to successful disease management. As the prevalence of asthma increases worldwide, there is concern about increasing numbers of patients with untreated or undertreated asthma, which may lead to deterioration in disease control, with direct effects on morbidity and mortality rates. The costs attributed to asthma translate into a considerable economic burden, from the direct costs of medical treatment to the costs incurred through lost work or school days. International treatment guidelines currently recommend early intervention with ICS therapy to improve lung function and disease control.

OBJECTIVE

This article reviews the role of therapy with ICSs, particularly budesonide, in improving the management of asthma in patients of all ages and in reducing the economic and social burdens of this disease.

RESULTS

Randomized, controlled clinical studies confirm the efficacy of early intervention with ICSs in patients with mild persistent asthma. Regular use of an ICS can reduce the number of exacerbations and hospitalizations in patients of all ages and with all disease severities.

CONCLUSIONS

Budesonide has a well-established efficacy and safety profile. Its once-daily dosing may contribute to improved adherence and cost-effectiveness.

Cost-effectiveness analysis of early intervention with budesonide in mild persistent asthma

BACKGROUND

The Inhaled Steroid as Regular Therapy in Early Asthma (START) study reported that early intervention with budesonide in mild persistent asthma reduces severe asthmatic events and improves symptom outcomes and lung function in adults and children.

OBJECTIVE

We sought to estimate the incremental cost-effectiveness of early intervention with budesonide, as observed within the START study.

METHODS

START was a randomized, 3-year controlled trial of budesonide in early onset mild asthma among 7165 subjects ages 5 to 66 years. Three age groups (5-10, 11-17, and >or=18 years) were studied separately and overall. Differences in the probability of emergency treatments, symptom-free days (SFDs), and costs of health care were determined. Incremental cost-effectiveness ratios were estimated from the health care payer and societal perspectives.

RESULTS

Compared with usual therapy, patients receiving budesonide experienced an average of 14.1 (SE, 1.3) more SFDs per year (P <.001), fewer hospital days (69%, P <.001), and fewer emergency department visits (67%, P <.05). From the health care payer perspective, the net cost of early use of budesonide was an additional US dollars 0.42 (SE, dollars 0.04) per day, and the resultant cost-effectiveness ratio was US dollars 11.30 (95% CI, US dollars 8.60-US dollars 14.90) per SFD gained. From the societal perspective, the cost offsets of lower absence from school or work reduced the net cost of early budesonide to US dollars 0.14 (SE, US dollars 0.07) per day and decreased the cost-effectiveness ratio to US dollars 3.70 (95% CI, US dollars 0.10-US dollars 8.00). Early intervention was more effective and cost saving in the youngest age group.

CONCLUSION

Long-term treatment with budesonide appears to be cost-effective in patients with mild persistent asthma of recent onset.

The effect of cost construction based on either DRG or ICD-9 codes or risk group stratification on the resulting cost-effectiveness ratios

BACKGROUND

As cost-effectiveness analyses (CEAs) are increasingly used to inform policy decisions, there is a need for more information on how different cost determination methods affect cost estimates and the degree to which the resulting cost-effectiveness ratios (CERs) may be affected. The lack of specificity of diagnosis-related groups (DRGs) could mean that they are ill-suited for costing applications in CEAs. Yet, the implications of using International Classification of Diseases-9th edition (ICD-9) codes or a form of disease-specific risk group stratification instead of DRGs has yet to be clearly documented.

OBJECTIVE

To demonstrate the implications of different disease coding mechanisms on costs and the magnitude of error that could be introduced in head-to-head comparisons of resulting CERs.

METHODS

We based our analyses on a previously published Markov model for HIV/AIDS therapies. We used the Healthcare Cost and Utilisation Project Nationwide Inpatient Sample (HCUP-NIS) data release 6, which contains all-payer data on hospital inpatient stays from selected states. We added costs for the mean number of hospitalisations, derived from analyses based on either DRG or ICD-9 codes or risk group stratification cost weights, to the standard outpatient and prescription drug costs to yield an estimate of total charges for each AIDS-defining illness (ADI). Finally, we estimated the Markov model three times with the appropriate ADI cost weights to obtain CERs specific to the use of either DRG or ICD-9 codes or risk group.

RESULTS

Contrary to expectations, we found that the choice of coding/grouping assumptions that are disease-specific by either DRG codes, ICD-9 codes or risk group resulted in very similar CER estimates for highly active antiretroviral therapy. The large variations in the specific ADI cost weights across the three different coding approaches was especially interesting. However, because no one approach produced consistently higher estimates than the others, the Markov model's weighted cost per event and resulting CERs were remarkably close in value to one another.

CONCLUSION

Although DRG codes are based on broader categories and contain less information than ICD-9 codes, in practice the choice of whether to use DRGs or ICD-9 codes may have little effect on the CEA results in heterogeneous conditions such as HIV/AIDS.

Cost-effectiveness of inhaled nitric oxide in the treatment of neonatal respiratory failure in the United States

OBJECTIVE

Two recent randomized controlled trials (RCTs) reported that inhaled nitric oxide (iNO) decreased the incidence of extracorporeal membrane oxygenation (ECMO) or death in term and near-term newborns with hypoxic respiratory failure. Our objective was to estimate the cost-effectiveness ratio of iNO in this population.

METHODS

We studied 1000 simulation cohorts (n = 483 for each cohort) of term/near-term newborns with hypoxemic respiratory failure. We conducted our study following US Public Health Service Panel on Cost-Effectiveness in Health and Medicine guidelines, adopting the US societal perspective. We constructed a decision tree reflecting iNO use, subsequent ECMO use, death, and long-term neurologic and respiratory morbidity in survivors, as determined from the combined outcomes of the 2 RCTs (n = 483). We estimated costs on the basis of length-of-stay data for the initial episode of care from 1 of the RCTs, unit costs from administrative data sets, and current pricing for iNO. We ran a Monte Carlo simulation to generate estimates of differences in costs and effects at 1 year, along with the stochastic uncertainty around these estimates. We expressed effects as quality-adjusted survival, assuming quality of life = 1 with no comorbidity, 0.7 with 1 comorbidity, and 0.49 (0.7 x 0.7) with 2 comorbidities. We constructed a base case, in which iNO was initiated at tertiary care ECMO centers (mimicking the RCTs) and a Public Health Service Panel on Cost-effectiveness in Health and Medicine reference case, in which iNO was initiated at the local hospital before transfer (mimicking real-world practice). We exposed our assumptions to a sensitivity analysis.

RESULTS

Direct application of the trial results (base case) suggested that iNO was both more effective and cheaper (cost savings of 1880 dollars per case despite acquisition costs of 5150 dollars, predominantly as a result of decreased need for ECMO), with 84.6% probability that the cost-effectiveness ratio was better than 100,000 dollars per quality-adjusted life-year. Under the reference case, iNO was also more effective (though slightly less so) and was even cheaper (cost savings of 4400 dollars per case), with 71.6% probability that iNO was cheaper and more effective and 91.6% probability that the cost effectiveness ratio was better than 100,000 dollars per quality-adjusted life-year. Sensitivity analyses showed these estimates to be sensitive to patient selection and the price of iNO but insensitive to assumptions regarding quality of life.

CONCLUSIONS

From a US societal perspective, iNO has a favorable cost-effectiveness profile when initiated either at ECMO centers or at local hospitals in term/near-term neonates with hypoxemic respiratory failure.

An update on the health economics of asthma and allergy

Health economics is receiving more attention as decision-makers--whether purchaser, physician, or patient--are looking for a more comprehensive understanding of the impact of adopting new healthcare strategies. In this article we review the recent advances in the health economics of asthma and allergy. In burden of illness studies, estimates of the economic burden of asthma and allergy were reported from countries and regions not previously detailing these costs. There were economic evaluations comparing medications and those that evaluated disease management programs. The recent studies of pharmaceuticals have focused on evaluating the cost-effectiveness of various controller medications for the treatment of asthma. Although mostly observational, such studies increase the evidence that these medications are relatively cost-effective. A few recent economic evaluations have been published examining disease management and education programs. These studies are generally long-term evaluations and have not shown consistent health economic impact. The field of health economics in asthma and allergy continues to evolve and aims to provide information to aid in decision making.

The inhaled Steroid Treatment as Regular Therapy in early asthma (START) study: rationale and design

Although the beneficial effects of treatment with inhaled steroids in asthma are widely accepted, the role of early intervention in patients with mild asthma remains unsettled. Conventional efficacy trials are often of short duration and involve highly selected patient populations that exclude many patients typical of those encountered in routine clinical practice. Hence, a large "real-world" effectiveness study is needed to evaluate the benefits of early intervention with inhaled steroids in patients with mild, persistent asthma. In the START (inhaled Steroid Treatment As Regular Therapy in early asthma) study, patients ages 6-60 years, from 31 countries and districts worldwide with mild persistent asthma, have been randomized to once-daily treatment with budesonide, 200 microg (for patients < 11 years) or 400 microg (for patients > or = 11 years), or placebo via Turbuhaler for 3 years. The double-blind treatment period will be followed by a 2-year period of open budesonide treatment. Throughout the study, other asthma medication including glucocorticosteroids can be given as judged appropriate by the investigator. Lung function will be measured by spirometry using standardized techniques at 3-month intervals throughout the study, and bronchodilator reversibility will be measured annually. The primary outcome measures are the time to the first severe asthma-related event during the first 3 years of the study and the change in postbronchodilator forced expiratory volume in 1 second (FEV(1)) from baseline during the entire 5-year study period. These measures have been chosen to reflect the progression of mild asthma toward more severe asthma and the extent of irreversible airflow limitation, which should reflect the degree of airway remodeling.