Joannie Shen; Michael Johnston; Ron D Hays

Disclosures

Expert Rev Pharmacoeconomics Outcomes Res. 2011;11(4):447-453. 

In This Article

Lung Function Tests

Symptoms and lung function tests are not strongly correlated with one another. Both symptoms and lung function should be monitored by clinicians who assess asthma control in clinical practice and analyzed separately in clinical trials. For example, improvement in symptoms can be achieved by using long-acting β-agonist therapy, which may occur without any change in FEV1 before bronchodilator (BD) use (pre-BD FEV1).[39]

Spirometry is one of the fundamental measures of asthma control; it provides an objective measure of airflow limitation caused by smooth-muscle contraction or structural changes. The measures relevant to asthma are: FEV1, forced vital capacity (as vital capacity or FEV6), FEV1 to forced vital capacity ratio, BD responsiveness (change in FEV1 after inhaled BD) and post-BD spirometric results. Pre-BD FEV1 has been used as the primary end point of lung function in most of the asthma clinical trials over the last three decades, based on the early focus on airway obstruction as the primary characteristic of asthma. Low FEV1 measures (pre-BD, on treatment or random) are independent predictors of subsequent AEs.[40–42] BD reversibility is also an independent predictor of death due to asthma.[41] BD responsiveness is only weakly associated with measures of AHR and airway inflammation, but is an independent predictor of response to inhaled corticosteroid therapy.[43]

Studies have found that pre-BD FEV1 is associated with most other measures of asthma control[44–46] but it correlates weakly with symptoms[47] and with disease-targeted HRQOL.[48,49] Changes in FEV1 over time are associated with changes in most other asthma outcome measures,[50] but such associations are generally poor (including airway inflammation indexes).[51] Taken together, these findings indicate that lung-function measurements provide complementary information to that provided by other measures.[52]

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