[Evaluation of a fast urease test for the detection of Helicobacter pylori]

Helicobacter Pylori colonize the gastric mucosa and their adaptation to this environment is related with its high activity urease. This enzyme hydrolyzes the gastric urea, neutralizing the acid environment of the bacteria. Based on that reaction numerous presumptive diagnosis tests, have been developed using a solution of urea (usually 6%) with a pH indicator (usually 0.05% fenol-red); nevertheless, the color changes are so light that some persons do not detect it. For that reason, a modification of that reaction was proposed using a mix of pH indicators (0.05% fenolred and 0.002 bromothymol blue) which induces a color change from light green to deep purple. Also, the reaction of urease was evaluated using only bromothymol blue. The reaction using fenol red as indicator showed the higher values for sensitivity of 58.8% and the specificity of 66.6%; whereas using only bromothymol-blue those values were 46 y 71.4% respectively. The efficiency of the test using fenol-red or the mix of this bromothymol- was 64.2 y 62.2%, respectively; however, the mix of indicators induce a change color easily detected, because of changes from ligh-green to deep-purple.