Vol. 13 •Issue 9 • Page 16
Allergy & Asthma
How to Assess Asthma Severity and the Implications for Treatment
Asthma has earned the dubious distinction of being the most common chronic disease in childhood.1 It carries an equally impressive price tag, accounting for $14 billion in total annual costs in 2002.2
In addition, a recent report showed that out of 29,430 asthma-related hospitalizations over a 12-month period identified in a 215-hospital database, approximately 11 percent involved admission to the intensive care unit and intubation.3
The morbidity and mortality associated with asthma continue to escalate despite advances in asthma diagnosis and therapy. Appropriate assessment and treatment are needed to minimize baseline symptoms and prevent potentially life-threatening asthmatic events.
SEVERITY OF DISEASE
The cornerstone of good asthma management consists of controller therapy for those patients in whom daily therapy is indicated and an action plan to execute at times of worsening signs and/or symptoms. However, the issues of which patients should be started on controller therapy and which controller therapy is most appropriate have sparked considerable controversy.
In an effort to improve the quality of care for asthma patients, various national organizations, including the National Heart, Lung, and Blood Institute, have developed and updated guidelines for the diagnosis and management of asthma.4 The manuscript was founded on evidence-based medicine and expert consensus when sufficient data were unavailable.
The guidelines suggest stratifying patients into groups to determine which patients are candidates for controller therapy and which therapy is most appropriate. Those groups include mild-intermittent, mild-persistent, moderate-persistent and severe-persistent.
The distinction between the groups is based on frequency of asthma symptoms and pulmonary function tests by peak flow meter or spirometry. Patients are classified into the severest category in which they possess one or more criteria. Thus, severity is based on baseline symptons and lung function while severity of individual asthma exacerbations isn’t a determining factor.
This classification system is designed to assist the practitioner at choosing appropriate controller therapy in those patients naíve to controller therapy. Patients who fall into the mild-intermittent group are treated with as-needed therapy (e.g., short-acting bronchodilators) only and don’t meet criteria for daily controller therapy.
However, the remaining three groups who have “persistent” asthma are all candidates for daily controller therapy. This system also has been used for escalating therapy and/or determining which patients are under suboptimal control. In general, the most severe patients require the most aggressive therapy. The guidelines further suggest starting “big” to control the disease and then “backing down.”
The importance of daily controller therapy when indicated can be illustrated best in those patients who are prescribed daily inhaled corticosteroids, which are the mainstay of asthma controller therapy. Inhaled corticosteroids have been found to improve asthma control when measured by both subjective and objective markers. They’ve been shown also to be life-saving.
In fact, the relative risk for hospitalization has been shown to be inversely related to the number of canisters of inhaled corticosteroids that are filled per person per year.5 What’s perhaps more impressive is that the risk of death from asthma has been shown to decrease dramatically with each additional canister of inhaled corticosteroids that’s obtained yearly.6
In most clinical practices, the severity of asthma is based on symptoms alone. When patients are questioned regarding both short-term and long-term asthma symptoms, slightly less than half are categorized as having mild-intermittent disease; approximately 20 percent are classified as having mild-persistent disease; and the remainder with moderate- to severe-persistent disease.8 These data appear to mimic prior surveys that also have categorized asthma severity of large populations.
Unfortunately, data from this same survey have suggested that both short-term and long-term asthma symptoms often will underestimate asthma severity as the functional impact of asthma; specifically addressing the physical, social and nocturnal aspects of asthma appears to provide a more realistic stratification of asthma severity.7 This disparity is likely due to the fact that asthma patients tend to overestimate their asthma control; a large portion of patients with moderate to severe disease will report that their disease is “well-controlled” or “completely controlled.”8
Many patients often will provide a history that’s consistent with mild and/or well-controlled asthma, but with further questioning it appears that their lives have been altered in some way to accommodate their poorly controlled asthma. A common example is found in those children who abstain from certain vigorous activities because they develop asthma-related symptoms such as, “Jimmy now plays baseball instead of soccer because baseball allows him to rest in between.”
A colleague recently reported a case of an adult woman with asthma who told him that asthma doesn’t control her life, yet she has always lived on first-floor apartments because she becomes incredibly “winded,” presumably from her asthma, when she walks up stairs.
The goals of asthma therapy clearly state, among other things, that asthma patients should be able to participate in normal activities of living, including vigorous ones. Many athletes, both amateur and professional, have asthma and continue to participate at a world-class level. Thus, health care professionals must continue to encourage asthma patients to pursue all those activities without limitation. Failure to participate in such activities is most often a function of suboptimal therapy and not severe disease.
Nevertheless, the importance of objective measures of asthma severity can’t be overlooked because there’s an abundance of data that suggests that symptoms don’t necessarily correlate with asthma severity based on spirometry or peak flows.9,10
Many patients who were previously categorized with a mild form of asthma later discover they have a more severe disease when they perform spirometry. Often these patients report little to no symptoms yet have abnormal spirometry. This is supported by the observation that these patients often report a clinical improvement after the initiation of controller therapy even though they report little to no symptoms prior to the initiation of therapy.
For example, many patients will deny asthma symptoms other than mild, intermittent symptoms responsive to short-acting bronchodialators. Based on symptoms alone, these patients would fall into the mild-intermittent category and therefore not be placed on asthma controller therapy.
However, many of these patients have abnormal PFTs and later will report a subjective improvement in exercise tolerance and other parameters after initiation of appropriate controller therapy. This suggests an improvement in their disease that was seemingly nonexistent before the initiation of daily therapy.
An analogous example would be those people who feel their vision is fine until they’re tested and provided corrective lenses, at which point they clearly appreciate an improvement in their vision. Therefore, lack of symptoms doesn’t negate the possibility for disease, particularly in the case of asthma.
Furthermore, lung function measured by spirometry has been shown to be positively associated with the risk of an asthma attack over the subsequent year after measurement.10 Serial PFTs, when feasible, should be considered for all patients with asthma. Unfortunately, younger children, particularly those who are infant and toddler age, present a unique diagnostic dilemma because they’ll rarely participate in the history and don’t have the skills necessary to adequately perform PFTs.
The most recent update of the guidelines has given special attention to those children with asthma under age 5 by classifying them as persistent if they fulfill certain criteria and have had greater than three exacerbations over the last year, or two or more exacerbations less than six weeks apart. Thus, many children now would be placed appropriately on controller therapy that previously wouldn’t have been considered for controller therapy.
Asthma is a variable disease by definition. In fact, during a 12-week period, the same group of patients has been shown to change groups.11 Therefore, it’s imperative that patients with asthma undergo serial assessments, including PFTs when available. Even patients with mild disease are at risk for negative outcomes including death.12
The nationally accepted guidelines have contributed to improved asthma screening and care; however, the guidelines are at best guidelines, and every asthma patient must be assessed and followed routinely on an individual basis.
Dr. Julius is a pediatric pulmonologist with Children’s Healthcare of Atlanta.
For a list of references, please call Sharlene George at (610) 278-1400, ext. 1324, or visit www.advanceweb.com/respmanager.