What is the most appropriate test for a 20-year-old female with mixed IBS symptoms who has not traveled abroad?

The most appropriate test for a 20-year-old female with mixed Irritable Bowel Syndrome (IBS) symptoms who has not traveled abroad is serologic screening for celiac disease. This is particularly relevant in this case because celiac disease can present with symptoms similar to IBS, such as abdominal pain, bloating, and changes in bowel habits.

Considering the age and symptomatology of the patient, screening for celiac disease is crucial as it can arise in individuals of this demographic. Early detection is important because untreated celiac disease can lead to complications such as malnutrition and increased risk of certain cancers. Serologic tests for celiac disease, particularly tissue transglutaminase antibodies (tTG-IgA) and endomysial antibodies (EMA), are reliable methods for initial screening in patients with gastrointestinal symptoms. If these tests are positive or the patient has risk factors, further confirmatory testing with an intestinal biopsy may be warranted.

In this scenario, options like food allergy testing and stool tests for ova and parasites are less appropriate as they do not address the possibility of celiac disease directly, particularly without travel history which might suggest infections. Gluten sensitivity testing is not recognized as a standard diagnostic test and can often lead to confusion, as