Asthma in adolescents and adults: Evaluation and diagnosis
●Clinical features
Asthma may develop at any age, although the majority of people with asthma are diagnosed in childhood. Obtaining the clinical history in an adult should include questions about the presence of symptoms earlier in life. Other historic clues that are highly suggestive of asthma include recurring, episodic symptoms, the presence of typical triggers (especially exercise, exertion in cold air, or allergen exposure), and a personal or family history of allergic disease.
●Physical examination
The physical examination may be normal in asthma. The presence of abnormal findings (such as wheezing) is suggestive of asthma, although not specific. Asthmatic wheezing is typically composed of multiple high-pitched sounds audible most prominently during expiration. Nasal examination with an office otoscope should be included to check for the pale, swollen mucosa of associated allergic rhinitis and for nasal polyps, which raise the possibility of aspirin-exacerbated respiratory disease.
●Evaluation:
•Pulmonary function testing
The pulmonary function tests most helpful in diagnosing asthma are spirometry pre- and post-bronchodilator, bronchoprovocation testing (usually with methacholine), and peak expiratory flow (PEF) monitoring. Expiratory airflow obstruction with a reversible reduction in the forced expiratory volume in one second (FEV1), heightened sensitivity to bronchoprovocative agents such as methacholine or exercise, and variability over time of >20 percent in PEF are findings consistent with asthma.
•Laboratory tests
Laboratory studies are sometimes indicated to identify potential asthma triggers and exclude alternative diagnoses, including blood tests (eg, complete blood count with white blood cell differential, total serum immunoglobulin E, and allergen-specific immunoassays), skin testing for environmental allergies, and a chest radiograph.
•Imaging
A chest radiograph is not routinely recommended as part of the diagnostic evaluation. However, many clinicians, including ourselves, obtain a chest radiograph in patients with atypical features (eg, chronic purulent sputum production, persistently localized wheezing, inspiratory crackles, fever, clubbing) and for new-onset, moderate-to-severe asthma in adults over age 40.
●Diagnosis
The diagnosis of asthma is based upon the presence or history of symptoms consistent with asthma (most commonly episodic cough, wheezing, or dyspnea provoked by typical triggers) combined with the demonstration of variable expiratory airflow obstruction. The strategies for using pulmonary function testing vary based on the results of initial spirometry.
•Spirometry pre- and post-bronchodilator (preferred)
The preferred approach to the diagnosis of asthma is the use of spirometry to identify reversible airflow obstruction. An obstructive pattern with an increase in FEV1 or FVC of >10 percent relative to the predicted value following administration of two to four puffs of a quick-acting bronchodilator is suggestive of asthma, especially if postbronchodilator spirometry is normal.
•Serial measurements of FEV1 or PEF
An alternative approach is to obtain serial measurements of FEV1 or PEF over time at home or in the office. Patients can track the results in a peak flow diary. A variability of >20 percent that corresponds to symptoms is strongly suggestive of asthma. PEF measurement can be combined with a therapeutic trial of inhaled bronchodilator.
•Bronchoprovocation testing when baseline spirometry normal
Bronchoprovocation testing, such as with a methacholine, mannitol, or exercise challenge, is typically reserved for patients in whom the baseline spirometry is normal and the diagnosis remains uncertain.
•History-based diagnosis
For clinical settings in which neither spirometry nor serial peak flow measurement is available, a diagnosis of probable asthma can be made based upon history alone, provided the patient has typical symptoms that respond promptly and completely to therapy. History-based diagnosis is also appropriate for urgent care settings when patients respond to asthma therapies as expected. Peak flow measurements are appropriate in these office-based and urgent care settings to supplement history and exam.
●Differential diagnosis
The differential diagnosis of asthma includes respiratory and non-respiratory conditions that may cause similar symptoms, wheezing on examination, and/or an obstructive pattern on spirometry. Evaluation should include assessment for conditions that may co-exist with asthma and worsen its severity.
●Social determinants of health
Asthma prevalence and morbidity are influenced by social determinants of health, and in the United States these factors have a disproportionate effect on certain populations. Consideration of these factors is important in the evaluation of the asthma patient.
●Referral
Consultation with an asthma specialist, either a pulmonologist or an allergist, is warranted when the diagnosis of asthma is uncertain, when the asthma is difficult to control, medication side effects are intolerable, or when a patient has frequent exacerbations.
