6.0 Bronchial Provocation (Challenge) Testing

When the physician assessing a patient is concerned that they might have asthma, first spirometry is performed. If no obstruction is identified further testing is sometimes required. A medication called methacholine is used to ‘provoke’ airway response.

When the airways of people with asthma are exposed to this medication, it will stimulate a response, which can be measured. If there is a positive response, asthma can be clearly identified and treated appropriately.

In most cases, methacholine challenge testing involves repeated FEV1 efforts at increasing levels of the drug. The sooner the patient reacts by a 20% reduction in their FEV1 compared to room air (normal) conditions the more likely their prevalence to asthma.

Challenge testing determines presence of airway hyper reactivity. After initial spirometry, patient inhales a specific concentration of methacholine chloride and spirometry is repeated. A reduction in FEV1 20% below the prior test indicates asthma.