Antigens and Antibodies
The other day, a physician’s assistant wrote an order for “H pylori Ab” on a lab requisition. One of the techs telephoned: IgG, IgA, or IgM? Naturally, he ordered all three and hung up. And I thought, this is getting a bit out of hand.
Did we ask the wrong question? When do we cross the line in questioning antigens and antibodies?
Guidelines published in the American Journal of Gastroenterology state “The urea breath test and stool antigen test are currently the most accurate noninvasive diagnostic tools and can be used with confidence... Cost-effectiveness studies suggest that the stool test and the urea breath test that detect active infection are preferable to serological tests in the United States.”
Insurance carriers (e.g. Aetna and Anthem) have adopted American Gastroenterological Association and American College of Gastroenterology guidelines to eliminate serology testing for active infection.
ARUP laboratories has a helpful flowchart algorithm for H. pylori testing that doesn’t list antibody testing. If the patient is over age 55 or has “alarm symptoms,” an esophagogastroduodenoscopy (that’s a mouthful, ha ha) is done, otherwise an H. pylori breath test or stool antigen test is performed.
Finally, WebMD -- read by patients -- summarizes Helicobacter pylori testing: “If you have antibodies to H. pylori in your blood, it means you either are currently infected or have been infected in the past.” For at least ten years I’ve promoted the stool antigen test “to support a diagnosis of H. pylori infection or to determine whether treatment for an H. pylori infection has been successful.”
Should we steer providers to order tests? Instead of asking, “Which antibody test do you want, because our reference lab does three of them?” ask, “Are you looking for active infection?”
If the PA answers, “Yes,” we can say, “The guidelines for adults say to perform a urea breath test or stool antigen test instead,” and offer to fax the algorithm. It’s appropriate to add information about test sensitivity and even give an opinion.
Does your laboratory ask what kind of antibody, switch to antigen testing, or ask the reason for the test?
NEXT: Sustaining Change