5th January 2024

A 45-year-old woman presents with 6-month history of dry nocturnal cough with no other symptoms

A 45-year-old woman presents with 6-month history of dry nocturnal cough with no other symptoms. On examination, she has BMI of 31, otherwise unremarkable. Chest X-ray is normal. Spirometry is done and shows FEV1 of 60%. What is the most appropriate investigation?

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