[1] The basis of the test is the ability of H. pylori to secrete the urease enzyme, which catalyzes the conversion of urea to ammonia and carbon dioxide.

The urease produced by H. pylori hydrolyzes urea to ammonia, which raises the pH of the medium, and changes the color of the specimen from yellow (NEGATIVE) to red (POSITIVE).

Among different kinds of rapid urease tests (liquid-based, gel-based, dry cool) there is a design type with single-layer sensitive element — a layer impregnated simultaneously with urea and an indicator composition.

The indicator would change color not in the course of the enzymatic reaction, which then causes alkalization of the medium as a result of ammonia formation, but under the effect of the pH of the gastric biopsy.

Ammonia formed during the hydrolysis of urea by urease penetrates through a special selective membrane to the layer impregnated with the indicator composition.