1st April 2022

A 26-year-old baker presents with episodic breathlessness

A 26-year-old baker presents with episodic breathlessness. He complains of feeling short of breath and wheezy over the past month, alongside some dry cough at night. This appears to improve slightly over the weekend when he is off work. He denies any family history of atopy. Physical examination was unremarkable.  

Which of the following would confirm the specific underlying diagnosis?

Select the SINGLE most appropriate option from the list below. Select ONE option only.