Urea Breath Test (UBT): Principle, Procedure, and Results

Urea breath test (UBT) is a qualitative and non-invasive rapid test for diagnosing infections of Helicobacter pylori (the primary cause of gastric and duodenal ulcers)Helicobacter pylori is a fastidious bacterium known to be a potent producer of the urease enzyme. Urease breaks urea in the stomach into ammonia and carbon dioxide, raising the pH of the environment surrounding the organism and allowing it to survive in the stomach’s acidic environment.

Find information about “Urease test and urease positive microorganisms HERE”.

Urea breath test is highly accurate (positive predictive value 100%, negative predictive value 98%) and extremely reliable for pretreatment diagnosis and post-treatment evaluation of “proof-of-cure”.

Principle of Urea Breath Test

Patients swallow test capsule which contains urea tagged with radioactive carbon14 i.e.  (14C-urea). If the patient is infected with H. pylori, the test urea will be broken down, producing a lot of 14CO2. This 14CO2 is quickly absorbed, moves from the blood to the lungs, and is exhaled in the breath, which is detected by the instrument in the breath of the patients.

Urea breath test working principle
Urea breath test working principle

Following ingestion of the capsule by a patient infected with H.pylori14CO2 excretion in the breath peaks between 15-20 minutes and declines thereafter. 14C-urea that is not hydrolyzed by H.pylori is excreted in the urine. If the patient is not infected with H. pylori, the urea will not degrade, and hardly any 14CO2 will be exhaled.

The detection in the breath differs among manufacturers. Some manufacturers have come up with an easier detection method. Currently, our laboratory uses the UBT test device of Headway. The working principle of their device is shown in this image.

Urea Breath Test Principle (Image source; Headway)

Uses of Urea Breath Test (UBT)

  • To find active cases of Helicobacter pylori infections:
    • To determine if a patient is actively infected with Helicobacter pylori pre- and post-therapy. A positive C14 Urea breath test only tells that the patient is actively infected with H.pylori.
    • A urea breath test may prevent patients with positive pylori serology (but no active infection) from being unnecessarily treated with broad-spectrum antibiotics. C14 Urea breath test comes positive only in the patients who are actively infected with H.pylori. H.pylori serology cannot reliably distinguish between past or present infection.
  • Monitoring the efficacy of the treatment: The C14 Urea breath test is generally accepted as the non-invasive test of choice for determining whether or not Helicobacter pylori eradication has been achieved. Even after successful treatment, serology may remain positive for six months or longer, so H.pylori serology will not reliably tell whether or not eradication of the organism has been achieved after the treatment. A C14 test may demonstrate eradication just 4-6 weeks post-treatment.

Guidelines for Patients

Physicians should provide appropriate information to patients before testing. This includes restrictions on medicine and the requirement to fast for a minimum of four hours (recommended 6 hours) before testing.

Common guidelines for the patients are as follows (please consult your physician before testing):

  1. Do not eat or drink anything, including water, for at least 4–6 hours before the test.
  2. Do not smoke for at least 2 hours before the test
  3. Stop taking all antibiotics, including triple therapy for Helicobacter pylori, at least four weeks before the test.
  4. Stop taking proton pump inhibitors at least one week before the test.

Sample Collection

  1. Swallow one urea [14C] capsule with water on an empty stomach or four hours after eating (food or drinks).
  2. Sit calmly for 10-15 minutes.
  3. Unpack and take out the mouthpiece and collection card body.
  4. Connect the mouthpiece to the front end of the collection card body.
  5. Blow reposefully through the mouthpiece for as long as possible.
  6. You can exchange breaths during blowing. DO NOT inhale from the mouthpiece!
  7. Blow continuously for 3-5 minutes until the indicator of the collection card turns from orange to yellow.
  8. Discard the mouthpiece into the dustbin. Hand over the collection card body to the operator for analysis and wait for the test results.

(Note: This sample collection process is based on the Helicobacter pylori test system and may vary according to the use of the detection system for radiolabelled carbon dioxide.)

Helicobacter Pylori Test System
Helicobacter pylori Test System

Results 

Detection of radiolabelled carbon dioxide  in the breath

  1. Some tests utilize a liquid scintillation counter to measure 14CO2 in breath samples.

In our settings, we use Helicobacter pylori test system to detect 14CO2 in breath samples.

Safety concerns

The test is considered safe in pregnancy or childhood. An issue that is frequently raised is the dose of radiation. The radiation dose received during C14 breath testing is equivalent to only three microsieverts (one-tenth the dose of a plain Chest-X ray and half the normal daily background exposure to radiation for everyday living).

References and Further Reading:

  1. The PYtest – The “Cutting Edge” Urea Breath Test to detect Helicobacter pylori 
  2. C14 Urea breath testing for Helicobacter pylori in general practice

Acharya Tankeshwar

Hello, thank you for visiting my blog. I am Tankeshwar Acharya. Blogging is my passion. As an asst. professor, I am teaching microbiology and immunology to medical and nursing students at PAHS, Nepal. I have been working as a microbiologist at Patan hospital for more than 10 years.

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