What is the role of spirometry in the diagnosis of asthma?

Updated: Nov 20, 2020
  • Author: Michael J Morris, MD, FACP, FCCP; Chief Editor: Zab Mosenifar, MD, FACP, FCCP  more...
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Spirometry assessments should be obtained as the primary test to establish the asthma diagnosis. Spirometry should be performed prior to initiating treatment in order to establish the presence and determine the severity of baseline airway obstruction. [62] Optimally, the initial spirometry should also include measurements before and after inhalation of a short-acting bronchodilator in all patients in whom the diagnosis of asthma is considered. Spirometry measures the forced vital capacity (FVC), the maximal amount of air expired from the point of maximal inhalation, and the forced expiratory volume in one second (FEV1). A reduced ratio of FEV1 to FVC, when compared with predicted values, demonstrates the presence of airway obstruction. Reversibility is demonstrated by an increase of 12% and 200 mL after the administration of a short-acting bronchodilator.

As a preliminary assessment for exercise-induced asthma (EIA), or exercise-induced bronchospasm (EIB), perform spirometry in all patients with exercise symptoms to determine if any baseline abnormalities (ie, the presence of obstructive or restrictive indices) are present. The assessment and diagnosis of asthma cannot be based on spirometry findings alone because many other diseases are associated with obstructive spirometry indices.

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