H Pylori Serology: Blood Test, Sensitivity & Interpretation

Instructor: Amy Albert

Amy is a Physician Assistant and certified professional coder. She holds a masters degree and has taught at the graduate school level.

Helicobacter Pylori otherwise known as H. Pylori is the bacteria responsible for causing gastric ulcers. H. Pylori can be detected through blood, stool and breath tests with high sensitivity and specificity.

There Is a Hole in My Stomach!

Once upon a time, physicians thought that gastric, or stomach ulcers, were caused by stress, spicy foods, and too much caffeine. Fast-forward to the year 2005, physicians discovered that those painful ulcers are actually caused by bacteria. In fact, the discovery that a pesky bacterium named Helicobacter Pylori could cause inflammation and ulceration in the stomach and small intestine won the Nobel Prize that year.

Now that physicians knew what causes stomach ulcers, they wanted to find a way test for it and treat it. It was relatively easy to find antibiotics needed to eradicate the H. Pylori infection. Unfortunately, it turned out that it was quite difficult to develop tests that were able to detect the presence of the bacteria.

Take a Deep Breath!

Fortunately, physicians developed not only a blood test but a breath test and stool test as well. Through blood, H. Pylori serology can be used to identify the presence or absence of the infection. A serology test is an antibody blood test. The H. Pylori blood test is testing for the presence of antibodies made by the body to attack the H. Pylori infection. If the antibodies are present, then the body has come into contact with H. Pylori. The H. Pylori serology test is highly sensitive and specific in diagnosing initial H Pylori infection. The problem is once your body makes antibodies to H. Pylori, it is possible to have them for the rest of your life! This means that even after being successfully treated for H. Pylori, your serology tests will most likely be positive.

Is It Gone?

Well, how do you know then if treatment has been successful and there is no longer an active infection? This is when the stool antigen test steps in. Once treated, the H. Pylori antigen stool test is used to determine if any H. Pylori antigens are present. An antigen is a foreign substance that activates the production of antibodies. H. Pylori antigens can be found in stool and when absent indicate that the infection has been eradicated. After antibiotic treatment, stool antigens return to normal more than 90 percent of the time.

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