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Helicobacter pylori: Overview and Considerations for Diagnostic Testing



Serology Limitations

Slide 19

August 2010

In answering this question, this is a situation where one needs to be aware of the advantages and disadvantages of the various types of tests used for detection of Helicobacter pylori.

False-positive serology tests are more common in low prevalence populations. Here is a graph which shows the effect of Helicobacter pylori prevalence on the positive predictive value, a positive test in the presence of disease, for a serological test.

According to Bayes’ theorem, when the prevalence of disease is low, most results are falsely positive. If you use the US seropositivity prevalence of 32.7%, the graph tells us the positive predictive value of a serology test would be just over 50%. If your community has a Helicobacter pylori prevalence of 20%, which is the case of much of the United States, the positive predictive value of a serological test will be less than 40%. Subsequently, the American College of Gastroenterology does not recommend use of serology in low prevalence populations.

To answer our question, if you do choose to utilize a serological test for Helicobacter pylori, because of issues with low positive predictive values, positive results should be confirmed with a noninvasive test that identifies active Helicobacter pylori infection, such as the urea breath test or the fecal antigen test.

Serology Limitations

 


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