On the basis of the bronchial provocation data presented in the following table, identify the PD20.

Question

Quizplus · Accepted Answer

Methacholine and mannitol are two very common inhalation challenge agents that have well-described protocols. In methacholine testing, a test is considered positive if the FEV₁ falls more than 20% from baseline. The concentration of the challenge drug is used as a marker of the degree of bronchial reactivity and is called the PD₂₀, the provocative dose that produces a 20% fall in FEV₁. For example, a patient with highly reactive asthma may have a fall in FEV₁ of 20% with a methacholine concentration of 0.25 mg/mL. A patient with mild asthma may experience a 20% fall in the FEV₁ at 10 mg/mL. In mannitol testing, a 15% decline in FEV₁ is considered a positive response. The patient presented in this question experienced clinically significant bronchial provocation at a methacholine dose of 10 mg/mL because the FEV₁ dropped 24% from baseline at that point.

On the Basis of the Bronchial Provocation Data Presented in the Following