COMMENTARY

Assessing Asthma in Kids: What Tools Work?

William T. Basco, Jr., MD, MS

Disclosures

March 15, 2017

Clinical Tools for Asthma Management

A recent review article, "Clinical Tools to Assess Asthma Control in Children,"[1] collates multiple subjective and objective measures that clinicians can use to determine whether a patient has asthma and whether asthma is adequately controlled.

The basic definition of controlled asthma includes the following:

  • Symptoms present no more than twice per week;

  • Use of rescue medications no more than twice each week;

  • Absence of nocturnal awakening;

  • No limitations of work or activity; and

  • A normal peak expiratory flow (PEF) or lung function measures.

Subjective Measures

The subjective measures available to clinicians include a detailed medical history, different composite asthma control scores, and quality-of-life measurements. The medical history should focus on frequencies of exacerbations and medication use but also lifestyle issues, such as limitations of daily activities and disturbances of sleep.

Many composite instruments have been used in different studies to measure asthma control. At least 17 survey or questionnaire instruments have at least one published validation study supporting their validity for measuring asthma control. These questionnaires vary by whom they query (parents or children) and by the age groups in which they have been validated. Questionnaires typically ask parents to rate their child's current asthma symptoms (including coughing, shortness of breath, and nocturnal symptoms) and assess how much asthma affects their child's participation in physical activities. Some also ask about exacerbations and markers for exacerbation, such as use of oral steroids.

Although these instruments are commonly used and have established validity on a population level to identify patients at higher risk of experiencing an exacerbation, their utility for individual children varies. Some instruments do not incorporate exacerbations as part of the assessment, events that can clearly have an impact. Quality-of-life measures also exist, but these have generally been confined to use in research studies and are not easily adapted to daily clinical use.

Objective Measures

Available objective measures include lung function, airway hyperreactivity, and biomarkers. Most clinicians are familiar with PEF or "peak flow" measurements—the highest flow rate achieved during a forced exhalation. The clinician should be interested in both the absolute value (compared with either the patient's best PEF or a predicted value based on the patient's height and sex) and in variability over time, an important advantage of PEFs. In general, the PEF is a proxy for the forced expiratory volume in the first second (FEV1). Patients can do multiple PEF measurements on their own without the need for full-blown spirometry, and the devices are both portable and inexpensive. One concern is the quality of effort for any individual measurement, especially when performed at home. Furthermore, it has not been shown that repeated PEF values are superior to clinician assessment of symptoms when taking a history.

Spirometry, or office-based lung function tests, provide multiple values to the clinician, most notably the FEV1. It is currently recommended that children with asthma have spirometry every 1-2 years as a way to objectively assess lung function. An advantage of spirometry is that because the tests are done in centers with well-trained clinicians, the results are highly reproducible and considered more accurate than PEF measurements. All spirometry measurements are compared against age- and sex-appropriate norms. Although clinicians primarily focus on FEV1, the forced expiratory flow between 25% and 75% of vital capacity value reflects flow through the small airways and may be abnormal even when the FEV1 is normal.

Normal spirometry does not rule out asthma because of the variable nature of symptoms. On the other hand, spirometry response to a bronchodilator challenge can be helpful in establishing the diagnosis of asthma. In a bronchodilator challenge test, the patient first completes spirometry, then inhales a short-acting bronchodilator. After a few minutes, the test is repeated. An improvement in FEV1 of ≥12% is considered a significant bronchodilator response. This can be used to assess the risk for future exacerbation and is a more objective measure to use in confirming the diagnosis of asthma or determining whether a patient's current asthma control is optimal.

Airway hyperresponsiveness can be assessed with a provocation method, typically using methacholine or exercise to evaluate whether FEV1 declines after the stimulus. A decline of ≥20% after exposure to methacholine suggests asthma, whereas a reduction of ≥10% with exercise indicates exercise-induced bronchospasm.

The review also explored the current state of biomarkers in asthma. Studies looking at exhaled nitric oxide, eosinophils in the sputum, and other microbiologic methods are considered experimental at present, and these biomarkers are not generally used in clinical practice.

Viewpoint

In summary, this article provides a brief but very informative overview of the different ways clinicians might assess asthma control or make the diagnosis in the first place. The full text of the article is available online; numerous links in the references to the pertinent records and the tools themselves are very valuable.

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