History of the problem of false positives
In the 1980s, with the problem
of false positive positives
faced Barry Marshall,
urease test CLO-test:
«When patients have excessive salivation or reflux of alkaline bile into the stomach, these fluids can contaminate the small gastric biopsy sample, such that the surface pH exceeds 6.0.»
photo by C.Northcott
from the site nobelprize.org
Researchers have linked inappropriate weak staining of some rapid urease tests to an elevated biopsy pH
«Когда у пациентов избыточное слюноотделение или рефлюкс щелочной желчи в желудок, эти жидкости способны контаминировать маленький образец желудочной биопсии, так что рН на его поверхности превышает 6.0»
Why is the test false staining possible?
1) Physiological reasons in the biopsy itself:
• In vitro study of the gastric mucous epithelium layer showed an average pH of 6.9
• measurements using microelectrodes showed that the pH of the gastric epithelium varies from 6.0 to 7.2 against the background of various factors
(the indicator bromothymol blue, used in rapid urease tests, changes color at pH above 6.5)
2) Contamination of the biopsy specimen with foreign alkaline agents as a result of
• throwing bile, the pH of which can be> 7.0
• chemical reactions caused by autolysis of gastric tissue cells
• exposure to lidocaine spray (contains sodium hydroxide)
• biopsy of blood on biopsy (normal blood pH> 7.3)
What are selective urease tests
Selective urease tests guarantee the response only to the products of the target enzymatic reaction, excluding the influence of the pH of the biopsy itself. In their design, the layers of the enzymatic and indicator reactions are separated
I sensitive layer: enzyme reaction
H. pylori urease and urea,
with the formation of ammonia (first reaction)
only the ammonia formed during the first reaction penetrates to the next layer
II Indicator reaction layer: Ammonia raises the pH (second reaction) resulting in a targeted color change
Express-test for the Detection of Helicobacter pylori Urease Activity in Biopsy Specimen
High sensitivity and speciﬁcity of AMA RUT Pro become possible thanks to it innovative multilayer design comprising a special membrane*.
It separates the enzymatic reaction layer from the indicator layer, so that the reaction with H. pylori urease and the following indicator reaction were not mixed. If the biopsy sample is H. pylori positive, the two reactions go consequently in the diﬀerent layers of the test, resulting in a bright color change within just minutes.
* WO2020139142 patent pending
The design solutions of the AMA RUT Pro medical device are protected by a patent in Russia and are being internationally patented "AMA" and "AMA RUT" are registered trademarks of the Association of Medicine and Analytics LLC
Зарегистрированным в России селективным уреазным тестом является экспресс-тест
AMA RUT, РУ № РЗН 2019/9301
Как и должно быть у селективного уреазного теста, в AMA RUT Pro
ферментативная и индикаторная реакции проходят в разных слоях.
quick and clear result
If the results are affected by extraneous pH
instead of H. pylori urease, why fast
urease tests recommended by Maastricht?
Because the global manufacturers of rapid urease tests changed their design (selective urease tests appeared), which made it possible to fundamentally eliminate the risk of inappropriate pH shift
Maastricht V: «In clinical practice, if there are indications for EGDS and there are no contraindications for biopsy, a rapid urease test is the diagnostic method of choice.
In case of a positive result, immediate therapy is required»
Ecology is an important topic today
Простой способ убедиться,
что селективный тест защищен
от срабатывания на pH биоптата
В отличие от индикаторной бумаги, селективный
уреазный тест AMA RUT Pro выдерживает воздействие раствора соды (рН = 8.0)
Memo for doctor on the use
Bend the block along the
Separate one segment for
Open the protective cover, but do not pull hard not to tear it off,
place the biopsy specimen
on the white reactive element,
and not beyond.
After placing the biopsy, gently smooth the protective cover with your finger around the perimeter of the test.
Fix the cover along the cut line.
Fixation is necessary to preserve
the reaction products in the
express test cell.
Evaluate the test result from the
back after 5 minutes.
Before using the express test, read the instruction for use,
included in the delivery package of the AMA RU Pro.
Manufacturing certified according to the international QMS
Since 2011, the Association of Medicine and Analytics LLC has been the first in Russia integrated quality management system that meets the requirements of GOST R ISO 9001 (ISO 9001) and GOST R ISO 13485 (EN ISO13485).
All production processes are validated in accordance with the GHTF (Global Harmonization Task Force) guidelines. A comprehensive system of internal control of the main and auxiliary production processes of test systems and equipment has been developed and implemented.