American Board of Internal Medicine (ABIM) Certification Practice Exam

Which of the following is NOT a noninvasive H. pylori testing modality?

1. Serology

2. Sheep blood agar culture

3. Fecal antigen test

4. Urea breath test

The correct answer is: Sheep blood agar culture

The correct answer, indicating which option is not a noninvasive testing modality for H. pylori, is based on the understanding of various testing methods used for diagnosing H. pylori infection. Noninvasive tests are those that do not require tissue samples or more invasive procedures. Serology is a noninvasive method that detects antibodies against H. pylori in the blood, providing information on the presence of an infection. Similarly, the fecal antigen test analyzes stool samples for antigens related to H. pylori, allowing for a straightforward and noninvasive diagnosis. The urea breath test is also a noninvasive procedure that measures carbon dioxide in the breath after the ingestion of a urea solution, indicating H. pylori activity. In contrast, sheep blood agar culture requires obtaining a sample from the stomach lining, which involves endoscopy and is considered an invasive procedure. This distinction is critical in understanding which methods fall under the category of noninvasive testing. Therefore, recognizing that culture methods typically involve more invasive techniques helps to clearly identify the correct answer to this question.