30th April 2024

A 50-year-old woman presents with a 6-month history of heartburn, particularly after meals and when lying down.

A 50-year-old woman presents with a 6-month history of heartburn, particularly after meals and when lying down. She also experiences a sour taste in her mouth and occasional difficulty swallowing. These symptoms partially improve with over-the-counter antacids. She denies any weight loss, vomiting, or evidence of gastrointestinal bleeding. Her BMI is 27 kg/m^2, and she has no significant past medical history.

Which investigation is most likely to confirm the diagnosis?