Background information respiration | Physiology | Spirometric testing | Testing

Diagnostic value of bronchodilation and provocation testing

Increased airway tone due to airway hyperresponsiveness forms the basis of the bronchodilator or reversibility test for asthma. According to the recommendations of the American Thoracic Society bronchodilator testing is regarded as unambiguous if the change in FEV1exceeds 12% of the predicted value. Increments in FEV1 or VC due to a bronchodilator drug of less than 8% (or < 150ml) are likely to be within measurement variability. Although accepted as diagnostic for asthma provided, that baseline measure of pulmonary function is < 80% of the predicted value, bronchodilation test offers relatively modest sensitivity and specificity.

In subjects with baseline pulmonary function within the normal range measurements of airway responsiveness to methacholine, histamine, or exercise may be helpful in establishing the diagnosis of asthma. After bronchial challenge testing a 15% fall in FEV1 or 20% decrease in PEF from baseline is diagnostic for airway hyperresponsiveness. With a high sensitivity but low specificity negative provocation testing may exclude the diagnosis of persistent asthma but a positive test is also likely to be found in patients with allergic rhinitis or patients with airflow limitations due to diseases such as cystic fibrosis, bronchiectasis or COPD.

Literature:

American Thoracic Society. Lung function testing: Selection of reference values and interpretative strategies. 1991. American Review of Respiratory Diseases; 144: 1202-1218

Chhabra SK. Acute bronchodilator response has limited value in differentiating bronchial asthma from COPD. 2005. Journal of Asthma; 42 (5): 367-372

O'Byrne P. GINA Executive Committee. Global strategy for asthma management and prevention. 2004. National Institutes of Health. Publication No 02-3659

Río-Navarro del BE, Hernández-Román MP, Espinola Reyna G, Berber A, Escalante-Domínguez AJ, González-Reyes M, Rosas-Vargas MA, Pérez-Lopez J, Baeza-Bacab M, Sienra-Monge JJL. A comparative study of bronchodilator reversibility with albuterol, between asthma symptomatic and asymptomatic children according to ISAAC Questionnaire in Mexico City. 2004. Allergologia et Immunopathologia; 32: 334-339

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