provocation inhalation challenge test; methacholine challenge test

Indications

• cough
• bronchospasm
• useful when diagnosis of asthma or reactive airway disease is uncertain, i.e. history suggestive of bronchospasm but normal spirometry

Contraindications

• pregnancy

Procedure

• Pulmonary function testing is performed before & after challenge with inhaled bronchospastic agent, methacholine, carbachol, histamine, mannitol, industrial irritants, exercise, isocapneic hyperventilation or cold air

Interpretation

• a 20% decrease in FEV1 from baseline is considered a positive test.
• up to 10% of normal individuals exhibit a positive provocation inhalation challenge test
• methacholine challenge is the most sensitive technique.

• generally a positive methacholine challenge with < 10 mg of methacholine is a sensitive indicator of asthma & a negative methacholine challenge with > 25 mg of methacholine rules out asthma.

* False-positive provocation inhalation challenge tests:

• allergic rhinitis
• congestive heart failure
• emphysema

More general terms

• pulmonary function test (PFT)