Pytest

Name: Pytest

Uses For Pytest

Urea C 14 is a radiopharmaceutical. It is used to diagnose stomach ulcers caused by a certain kind of bacteria known as Helicobacter pylori or H. pylori.

This agent is taken by mouth. If any H. pylori bacteria are present in the stomach, they will cause the urea C 14 to be broken down into radioactive carbon dioxide gas. When you breathe out by the mouth, the amount of radioactive carbon dioxide can be measured to see whether the bacteria are in your stomach.

This agent is a radioactive agent. However, with the small amounts in the capsule that is used for the test, the radiation your body receives is very low and is considered safe.

This agent is to be given only by or under the direct supervision of a doctor with specialized training in nuclear medicine.

Pytest Side Effects

Along with its needed effects, a medicine may cause some unwanted effects. This agent does not usually cause any side effects. However, if you notice any unusual effects, check with your doctor.

Clinical Pharmacology

The urease enzyme is not present in mammalian cells, so the presence of urease in the stomach is evidence that bacteria are present. The presence of urease is not specific for H.pylori, but other bacteria are not usually found in the stomach. The principle of the breath test is shown in Figure 1.

Figure 1: Principle of Breath Test

To detect H.pylori, urea labeled with 14C is swallowed by the patient. If gastric urease from H.pylori is present, urea is split to form CO2 and NH3 at the interface between the gastric epithelium and lumen and 14CO2 is absorbed into the blood and exhaled in the breath.

Following ingestion of the capsule by a patient with H.pylori, 14CO2 excretion in the breath peaks between 10 and 15 minutes and declines thereafter with a biological half-life of about 15 minutes. 14C-urea that is not hydrolyzed by H.pylori is excreted in the urine with a half-life of approximately 12 hours. About 10% of the 14C remains in the body at 72 hours and is gradually excreted with a biological half-life of 40 days.

Indications and Usage

PYtest1 (14C-Urea Breath Test) is indicated for use in the detection of gastric urease as an aid in the diagnosis of H.pylori infection in the human stomach. The test utilizes a liquid scintillation counter for the measurement of 14CO2 in breath samples.

Contraindications

None

Warnings

None

Dosage and Administration

Materials provided

As shown in Figure 2, the PYtest1 Kit contains:

  • PYtest1 capsule
  • Two 30 mL disposable cups
  • One drinking straw
  • One mylar collection balloon
  • One report form
  • One mailing box with labels2

Figure 2: PYtest1 Kit

2 The kit includes analysis by Kimberly-Clark of one balloon from one patient at one time point.

Materials Needed but not Provided

  1. Stopwatch/Timer capable of timing an interval up to 10 minutes.
  2. Water (40mL)

Dosage

One PYtest1 capsule.

Procedural Notes

  • Inform the patient to fast for 6 hours prior to the test.
  • The patient should be off antibiotics and bismuth for 1 month, and proton pump inhibitors and sucralfate for 2 weeks prior to the test.
  • Have patient sitting at rest while doing the test.
  • The capsule should not be handled directly as this may interfere with the test result.
  • To avoid contamination by bacteria in the mouth, the capsule should be swallowed intact. Do not chew capsule.

Step by Step Procedure for Balloon

Table 3: Breath Sample Collection by Balloon
Before the test
  1. Label balloon and fill in breath test report form.
  2. Check that all materials are present.
Minus 1
  1. Open the package containing the 14C-urea capsule minute and tip the capsule into the empty 30 mL cup. Do not handle the capsule directly.
  2. Hand the cup to the patient.
  3. Fill the second cup with 20 mL lukewarm water.
0 minute
  1. Ask the patient to tip the capsule directly into his/her mouth, then swallow it with the 20 mL of lukewarm water.
  2. Start the stopwatch when the patient swallows the capsule.
  3. Discard waste (e.g., capsule packaging, used straws) according to your facility's regulations.
3 minutes Ask the patient to drink another 20 mL of lukewarm water (in case the capsule may have lodged in the esophagus and not yet reached the gastric mucosa).
10 minutes
  1. Push a drinking straw into the neck of the balloon.
  2. Ask the patient to hold his/her breath for 5-10 seconds, then blow up a balloon with a slow breath through the straw, filling the balloon completely.
  3. Tie the neck of the balloon into a tight knot.
  4. Check that the balloon label and the breath test report form are completed correctly.
After the test Place the filled balloon and breath test report in the box and forward to Kimberly-Clark for analysis.

Quality Control

A minimum of 1 mM of CO2 is required to perform analysis of a breath sample. The amount of breath required to provide 1 mM of CO2 varies depending on the amount of CO2 the patient is producing. Since a full balloon typically contains at least 1 mM of CO2, the balloon should be completely filled.

Results

Interpretation of results (10 minute sample)
     <50 DPM Negative for H.pylori
     50-199 DPM Indeterminate for H.pylori
     ≥200 DPM Positive for H.pylori

The indeterminate result should be evaluated by repeating the PYtest1 or using an alternative diagnostic method. If repeat breath testing is undertaken, careful history to exclude confounding factors should be obtained. If confounding factors are present, wait an appropriate time (refer to Table 4) before repeating the PYtest1.

The cutoff point of 50 DPM was determined to be the mean + 3SD of results obtained in patients who did not have H.pylori.

DPM = Disintegrations per minute

Table 4: Factors which might cause sub-optimal breath test results
Factor Result Comment
Recent antibiotic or bismuth (Pepto-Bismol, etc.) false neg. Relapse of partially treated Hp may take 1-4 weeks.
Omeprazole (or other proton pump inhibitors) false neg. These agents suppress Hp in 40% of patients. Discontinue for at least 2 weeks before performing the PYtest1.
Resective gastric surgery false neg. Isotope may empty rapidly from the stomach.
Resective gastric surgery false pos. Patient may be achlorhydric and have bacterial overgrowth (non-Hp urease).
Food in stomach (also bezoar, gastroparesis) unknown Isotope may not come into contact with gastric mucosa. Patient may be achlorhydric and/or have bacterial overgrowth (non-Hp urease).

Expected Values

As shown in Figure 3 approximately 30% of patients tested will be positive for H.pylori.

Figure 3: Histogram showing DPM distribution for the PYtest1.

Note: DPM groupings were calculated on a logarithmic scale. Empty DPM groupings were not included. Chart includes all patients from Studies 1 and 2.

Frequency of DPM group includes samples with DPM < Group Name.

     DPM = Disintegrations per minute

     Gold Standard = Agreement between histology and CLOtest1

If the capsule is damaged or appears abnormal in any way, it may give inaccurate results.

How Supplied

PYtest1 Kit (14C-Urea Breath Test) is supplied as a kit containing a PYtest1 Capsule, a clear gelatin capsule containing 1µCi of 14C-urea and breath collection equipment.

PYtest1 Capsules are also supplied separately in unit dose packages of 1,10 and 100.

The PYtest1 Capsule has a shelf life of two years. The expiration date is printed on the capsule label.

PYtest1 Capsules and Kit should be stored at 15°-30°C (59°-86°F) in an area designated by each individual institution's regulations.

Rx Only

Kimberly-Clark Distributed in the U.S. by Kimberly-Clark Global Sales, LLC,
Roswell, GA 30076 USA
In USA, please call 1-800-KCHELPS • www.kchealthcare.com
Kimberly-Clark, Roswell, GA 30076 USA
Kimberly-Clark N.V., Belgicastraat 13, 1930 Zaventem, Belgium
Sponsored in Australia by Kimberly-Clark Australia Pty Limited; 52 Alfred Street,
Milsons Point, NSW 2061 • 1-800-101-021
©2003 KCWW. All rights reserved.

14-63-136-0-00/70080910 12/07

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