A 60-year-old woman presents with a 6-month history of persistent dry cough, unresponsive to simple linctus and a trial of omeprazole. She denies smoking, wheeze, or heartburn. Examination and chest X-ray are normal. Spirometry shows FEV1 85% predicted, FVC 88% predicted, FEV1/FVC ratio 0.77. She was started on Ramipril for hypertension 8 months ago. What is the most appropriate next step?