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PYtest (C-Urea Capsules) | PYtest [Avent, Inc.] | BioPortfolio

13:34 EST 27th January 2019 | BioPortfolio

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PYtest (C-urea capsules) is intended for use in the detection of gastric urease as an aid in the diagnosis of Helicobacter pylori (H. pylori) infection in the human stomach. The test utilizes a liquid scintillation counter for the measurement of CO in breath samples. The capsules are to be used when analysis is planned at the site where the sample is taken.

PYtest capsule is a gelatin capsule for oral administration containing 1 µCi of C labeled urea. The urea is adsorbed on sugar spheres and colored yellow with fluorescein.

Structural Formula (C-urea): NH CONH

Radiation emission: beta-emission, 49 keV, 156 keV, no other emissions

External emission: No external radiation hazard. Low-energy beta emissions only.

Maximum range of 0.3 mm in water.

Radiological Half-life: 5730 years

Maximum effective dose equivalent (EDE) : 0.3 mrem/µCi

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 C is swallowed by the patient. If gastric urease from H. pylori is present, urea is split to form CO and NH at the interface between the gastric epithelium and lumen and CO is absorbed into the blood and exhaled in the breath.

Following ingestion of the capsule by a patient with H. pylori, CO excretion in the breath peaks between 10 and 15 minutes and declines thereafter with a biological half-life of about 15 minutes. C-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 C remains in the body at 72 hours and is gradually excreted with a biological half-life of 40 days.

Two studies were performed. In both studies, patients with gastrointestinal symptoms underwent the breath test and an endoscopy. During the endoscopy, biopsy samples were taken from the antral gastric mucosa for histological analysis (2 samples, Giemsa stain) and rapid urease test (1 sample, CLOtest). Breath samples were mailed to the TRI-MED lab where they were read in a liquid scintillation counter.

Results were reported as disintegrations per minute (DPM). Analysis for accuracy used the ten minute breath sample. A breath sample DPM <50 was defined as a negative result. DPM ≥ 200 was defined as a positive result. DPM in the range of 50–199 was classified as indeterminate.

Of 186 patients who had histopathology and CLOtest (80 men, 106 women), 53 were infected with H. pylori as determined by agreement between histology and CLOtest. The study results are summarized below:

Table 1: Study #1 (n = 186, Indeterminate results included)
Histology and CLOtest
H. pylori Positive Negative Total
Notes: PYtest at 10 min. was compared to the gold standard of biopsy results in which histology and CLOtest concurred. Patients who did not have both biopsy tests performed, or in whom the tests differed, were excluded from analysis. There was no statistical difference in test accuracy based on gender of patient.
ppv = positive predictive value (true positive divided by total PYtest positive)
npv = negative predictive value (true negative divided by total PYtest negative)
PYtest Positive 51 8 59 ppv. 86%
(DPM Indeterminate 1 8 9
10 min.) Negative 1 117 118 npv. 99%
Total 53 133 186
sensitivity specificity
96% 88%

Breath tests were performed on 436 outpatients attending gastroenterology practices at sites in the United States. Seventy-six patients (40 men, 36 women) who had histology and CLOtest were evaluated. The results are summarized below:

Table 2: Study #2 (n = 76, Indeterminate results included)
Histology and CLOtest
H. pylori Positive Negative Total
Notes: PYtest at 10 min. was compared to the gold standard of biopsy results in which histology and CLOtest concurred. Patients who did not have both biopsy tests performed, or in whom the tests differed, were excluded from analysis. There was no statistical difference in test accuracy based on gender of patient.
ppv = positive predictive value (true positive divided by total PYtest positive)
npv = negative predictive value (true negative divided by total PYtest negative)
PYtest Positive 22 0 22 ppv. 100%
(DPM Indeterminate 4 2 6
10 min.) Negative 1 47 48 npv. 98%
Total 27 49 76
sensitivity specificity
82% 96%

PYtest (C-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 CO in breath samples.

None

None

After the patient ingests the C-urea capsule, the sample collected for test purposes is for in vitro diagnostic use only.

A false positive test could occur in patients who have achlorhydria. Very rarely, a false positive test may occur due to urease associated with Helicobacters other than H. pylori (i.e. Helicobacter heilmanni).

Persons concerned about very low doses of radioactivity may postpone the test or may decide to use an alternative means of diagnosis. The test produces radiation exposure equal to 24 hours of normal background. In animal experiments, such low doses of radiation do not carry measurable risk.

Preclinical studies were not conducted on C-urea. The estimated dose equivalent received from a single administration of PYtest (1 µCi C) is about 0.3 mrem.

It is necessary for the patient to fast for 6 hours before the test. The patient should also be off antibiotics and bismuth for 1 month, and proton pump inhibitors and sucralfate for 2 weeks prior to the test. Instruct the patient not to handle the capsule directly as this may interfere with the test result. The capsule should be swallowed intact. Do not chew the capsule.

No studies have been conducted with C-urea to evaluate its potential for carcinogenicity, impairment of fertility, or mutagenicity.

Antibiotics, proton pump inhibitors, sucralfate, and bismuth preparations are known to suppress H. pylori. Ingestion of antibiotics or bismuth within 4 weeks and proton pump inhibitors or sucralfate within 2 weeks prior to performing the test may give false negative results.

Animal reproduction studies have not been conducted with PYtest (C-urea). It is also not known whether PYtest can cause fetal harm when administered to a pregnant woman or can affect reproduction capacity. PYtest should be given to a pregnant woman only if clearly needed.

It is not known whether this drug is excreted in human milk. Because many drugs are excreted in human milk, caution should be exercised when PYtest is administered to a nursing woman.

Clinical studies in children have not been conducted. However, PYtest is expected to work the same in children as in adults. While the dose (1 capsule) does not need to be adjusted, the child must be able to swallow the intact capsule and blow into a straw.

No adverse reactions were reported in clinical trials.

Risk from radiation is negligible even with a 1000 capsule overdose (0.3 rem). If overdose occurs, the patient may drink one glass of water (150 ml) every hour to hasten excretion of the isotope. Maximum excretion of urea is achieved at a urine output of ≥ 2.0 ml/min.

FOR ANALYSIS AT TEST SITE BREATH SAMPLE COLLECTED INTO BALLOON (RECOMMENDED METHOD; SEE FIGURE 2)

Figure 2: Other Components

FOR ANALYSIS ON SITE BREATH SAMPLE COLLECTED INTO VIAL

CAUTION: Kimberly-Clark does not endorse breath sample collection by this method because patients might come into direct contact with the hyamine.

Figure 3: Typical Safety Trap

One PYtest capsule.

Breath Sample Collection by Balloon
Before the test Label balloon and fill in breath test report form. Check that all materials are present.
Minus
1 minute
Open the package containing the 14C-urea capsule and 1 minute tip the capsule into the empty 30 ml cup. Do not handle the capsule directly. Hand the cup to the patient. Fill the second cup with 20 ml lukewarm water.
0 minute Ask the patient to tip the capsule directly into his/her mouth, then swallow it with the 20 ml of lukewarm water. Start the stopwatch when the patient swallows the capsule. 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 Push a drinking straw into the neck of the balloon. 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. Tie the neck of the balloon into a tight knot. Check that the balloon label and the breath test report form are completed correctly.
After
sample
collection
See test analysis procedure.
Breath Sample Collection by Vial
CAUTION: Kimberly-Clark does not endorse the collection of breath samples by this method for patient safety reasons.
Before the
test
Label vial and fill in breath test report form. Vial label should include the patient's name, date of sample collection and time sample is taken. Check that the vial contains 2.5 ml of collection fluid (1.5 ml methanol, 1.0 ml 1 molar hyamine, two drops thymolphthalein pH indicator). Check that all materials are present.
Minus
2 minutes
Attach a straw to the safety trap (Figure 3).
Minus
1 minute
Open the package containing the 14C-urea capsule and tip the capsule into the 30 ml cup. Do not handle the capsule directly. Hand the cup to the patient. Fill the second cup with 20 ml lukewarm water.
0 minute Ask the patient to tip the capsule directly into his/her mouth, then swallow it with the 20 ml of lukewarm water. Start the stopwatch when the patient swallows the capsule. Discard waste (e.g., capsule packaging, used straw) 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 Ask the patient to hold his/her breath for 5–10 seconds, then blow bubbles into the collection fluid via the safety trap. The patient should blow bubbles until the fluid turns clear. Put lid on vial.
After
sample
collection
See test analysis procedure.

BALLOON READ ON-SITE:

VIALS READ ON-SITE

See steps 12–14 under "Balloon read on-site."

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

The indeterminate result should be evaluated by repeating the PYtest 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 identified, wait an appropriate time (refer to table 3) before repeating the PYtest.

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

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
Table 3: 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. Discontinuefor at least 2 weeks before performing the PYtest.
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).

As shown in Figure 4 approximately 30% of patients tested will be positive for H. pylori.

Figure 4: Histogram showing DPM distribution for the PYtest.

*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.

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

PYtest Capsules, clear gelatin capsules each containing 1 μCi of 14C-urea in unit dose packages of 1, 10 and 100.

PYtest Kit (C-urea breath test) is also supplied as a kit containing a PYtest Capsule and breath collection equipment.

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

PYtest 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 (USA)

U.S. Patent Nos. 4,748,113; 4,830,010

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.
14-63-133-0-00/70080916

HALYARD*

PYtest* C-UREA BREATH TEST CAPSULES FOR THE DETECTION OF HELICOBACTER PYLORI

Contents – 10 PYtest* Capsules each containing 1 µCi C-Urea

For dosage information, please see package insert

C-Urea (5730 yr1/2, 156 keV β-emission)

NDC 42536-6044-2

For In Vitro Diagnostic Use

Rx Only

Store at 15°–30°C (59°–86°F)

REF60442

Manufacturer

Avent, Inc.

Active Ingredients

Source

Drugs and Medications [1 Associated Drugs and Medications listed on BioPortfolio]

Pytest [avent, inc.]

PYtest Kit (C-Urea Breath Test)

Clinical Trials [0 Results]

None

PubMed Articles [0 Results]

None

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