Instead, asthma severity can fluctuate markedly over time, according to a study presented today at CHEST 2002, the annual meeting of the American College of Chest Physicians. Patients not taking controller medications can frequently move between severity categories -- a patient classified with a particular severity of asthma one week may exhibit symptoms or lung function findings consistent with another severity classification the next. As a result, discrete measurements of lung function, albuterol use or asthma symptoms taken on any given day may not provide an accurate picture of overall asthma severity and stability.
The study has important implications for how asthma patients are managed and the measurements physicians use to assess asthma severity. This study may also provide new insight into why both patients and physicians tend to underestimate the severity of asthma.1
The study, a retrospective analysis of two previously conducted 12-week clinical trials that included patients who had used only beta2-agonists (such as albuterol or salmeterol) for their asthma and were subsequently randomized to receive placebo and as-needed albuterol. GlaxoSmithKline researchers identified 85 such patients in these trials. The daily diary data from these patients -- which included asthma symptoms, albuterol use and peak expiratory flow (a measure of lung function) -- were reviewed to determine asthma severity based on criteria established by the National Institutes of Health.
The key finding: patients had marked fluctuations in the severity of their asthma. At study baseline, all patients met the criteria for moderate-to-severe asthma, having a mean baseline FEV1 (a measure of lung function) of 64 percent predicted and asthma symptoms and albuterol use 6.0 days per week and 4.7 days per week, respectively. However, the percent of weeks the subjects in these studies met criteria for intermittent, mild, moderate or severe asthma were 9.2 percent, 13.6 percent, 71.1 percent and 6.1 percent of weeks, respectively. These data were based on symptom scores, peak expiratory flow and albuterol use.
"The data demonstrate that asthma not controlled with maintenance medications can be a variable and unpredictable disease, with severity that changes from week to week," said Paul Dorinsky, MD, the study's lead author. "Physicians should recognize that asthma that may initially be thought to be 'mild,' frequently becomes more severe if these patients are followed over time."
No one parameter reliably predicted overall severity for individual patients at any given point in time. Failure to take this into consideration could possibly result in either an underestimation or overestimation of asthma severity.
Asthma is a chronic lung disease. Both inflammation (swelling and irritation) and constriction (tightening of the muscles around the airways) cause the airways to narrow, leading to symptoms that include cough, wheezing, shortness of breath and chest tightness. Though there is no cure, advances in research and preventative treatments in the past decade have made asthma a more controllable condition.
Yet, for many of the 24.7 million Americans who have been diagnosed with asthma at some point in their lives,2 the disease remains out of control. Each year, asthma accounts for approximately 5,000 deaths,2 500,000 hospitalizations,3 two million emergency department visits,2 14 million missed school days4 and 14.5 million missed work days.4 In 2000, asthma cost the U.S. economy an estimated $14 billion.5
According to national and international treatment guidelines, patients with persistent asthma can be classified into one of three categories (mild, moderate or severe) based upon lung function, asthma symptoms, nighttime awakenings and exacerbations. The study was conducted to determine whether a possible limitation of this classification system is that patients might not remain in any one severity category over time. The study findings suggest that this is indeed the case for patients who have not yet been prescribed an inhaled corticosteroid.
The variability of asthma, and the limitations of point-in-time assessments, may contribute to an underestimation of disease severity for individual patients. Ultimately, this may lead to unnecessary asthma morbidity and, perhaps, mortality.
The findings reinforce the importance of proper asthma management, including the use of daily maintenance treatments (if prescribed), to help keep asthma well controlled.
Sources
1. Asthma in America, October 1998; Schulman, Ronca and Bucuvalas, Inc. and Glaxo Wellcome Inc. For more information about the survey and its methodology, visit http://www.AsthmaInAmerica.com.
2. American Lung Association. Epidemiology and Statistics Unit, Best Practices and Program Services. Trends in Asthma Morbidity and Mortality. February 2002.
3. National Center for Health Statistics. 2000 National Hospital Discharge Survey, Advanced Data No. 329. June 2002.
4. US Centers for Disease Control and Prevention. Surveillance for asthma: United States, 1980-1999. Morbidity and Mortality Weekly Report 2002;51(SS01):1-13.
5. National Heart, Lung, and Blood Institute. Morbidity and Mortality: 2002 Chart Book on Cardiovascular, Lung, and Blood Diseases. May 2002.