Raman is a 44 year old software engineer who has been suffering with symptoms of indigestion. He admits a poor diet high in fatty foods and is a smoker. He denies symptoms such as exertional chest pain, weight loss or dysphagia. Abdominal examination is unremarkable. You decided to treat his symptoms with a protein pump inhibitor and to test for Helicobacter Pylori.

Which one of the following tests is not used to test for Helicobacter. Pylori?