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Stool Test: H. Pylori Antigen

What It Is

Helicobacter pylori (H. pylori) bacteria are a common cause of peptic ulcers (sores in the lining of the stomach, small intestine, or esophagus). In this test, a stool (feces) sample is used to determine if H. pylori antigens are present in your child's gastrointestinal (GI) system. Antigens are substances that trigger the immune system to fight infection.

Why It's Done

A doctor may request an H. pylori antigen stool test if your child has symptoms that could indicate the presence of a peptic ulcer, such as indigestion, abdominal pain, a full or bloated feeling, nausea, frequent belching, or vomiting. A test also might be ordered after your child completes a course of antibiotics for H. pylori to determine whether it eradicated the infection.

Preparation

Unlike most other lab tests, a stool sample is often collected by parents at home, not by health care professionals at a hospital or clinic. For 2 weeks before the test, your child may be asked to avoid certain medications such as antibiotics, antacids, bismuth, and peptic ulcer medicines such as proton pump inhibitors (PPIs) and H2 blockers.

Procedure

The doctor or hospital laboratory usually will provide written instructions on how to collect a stool sample. If instructions aren't provided, here are tips for collecting a stool sample from your child:

• Be sure to wear protective gloves and wash your hands and your child's hands afterward.
• Some young kids can't always let a parent know in advance when a bowel movement is coming. So a hat-shaped plastic lid is used to collect the stool specimen. This catching device can be quickly placed over a toilet bowl, or under your child's bottom, to collect the sample. Using a catching device can prevent contamination of the stool by water and dirt. Another way to collect a stool sample is to loosely place plastic wrap over the seat of the toilet. Then place the stool sample in a clean, sealable container before taking it to the lab.
• Plastic wrap can also be used to line the diaper of an infant or toddler who isn't yet using the toilet. The wrap should be placed so that urine runs into the diaper, not the wrap. Stools shouldn't be allowed to touch the inside of disposable diapers because the lining usually has antibacterial properties that can interfere with the test results.
• Your child shouldn't urinate into the container. If possible, have your child empty his or her bladder before a bowel movement.
• The stool should be collected into clean, dry plastic jars with screw-cap lids. Your child may be asked to provide a stool sample one or more times. For best results, the stool should be brought to the lab right away. If this isn't possible, the stool should be refrigerated and then taken to the lab as soon as possible.

Alternatively, a doctor or nurse may collect a small stool sample by inserting a swab into your child's rectum.

What to Expect

When the sample arrives at the laboratory, a small amount of stool is placed in tiny vials. Specific chemicals and a color developer are added. At the end of the test, the presence of a blue color indicates the presence of H. pylori antigens.

Risks

No risks are associated with collecting stool samples.

Helping Your Child

Collecting a stool sample is painless. Tell your child that collecting the stool won't hurt, but it has to be done carefully. A child who's old enough might be able to collect the sample alone to avoid embarrassment. Tell your child how to do this properly. If the sample is collected by swabbing, your child may feel slight pressure in his or her rectum during the procedure.