17th February 2025

A 25-year-old man attends the respiratory clinic with difficulty in breathing over the last 4 months.

A 25-year-old man attends the respiratory clinic with difficulty in breathing over the last 4 months. He describes feeling wheezy and having to take breaks at work due to breathlessness. His past medical history is only that of eczema. He has no recent travel, other than a trip to see family in Scotland a few weeks ago, where he felt his breathing was slightly better. He is a non-smoker and works as a building site manager.

In the clinic today, his observations are all within normal limits and his chest sounds clear. What would be the most appropriate investigation to confirm the likely diagnosis?

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