Investigating a persistent cough in an otherwise well patient

Tim, 36, has a 10-week history of dry cough

Tim, 36, has a 10-week history of dry cough. He is a builder and very fit. He wears protective gear for asbestos exposure and is a lifelong non-smoker.

His past history includes childhood asthma and minor musculoskeletal injuries. He takes no regular medications and has no known medication allergies. He has no known family history, including lung disease.

Tim describes initial flu-like symptoms, then a persistent dry cough with nocturnal wheeze. A few courses of antibiotics improved his symptoms marginally. He is prescribed a tapering course of prednisone and an asthma inhaler.

He denies weight