Purpose: to determine the effects of contaminants and diverse experimental conditions on the performance of commercially available rapid urease tests. Methods: the sensitivity of CLO (Tri-Med Specialties, Inc., Overland Park, KS), hpfast (GI Supply, Camp Hill, PA), and PyloriTek (Serim Research Corp, Elkhart, IN) for detection of H. pylori were calculated using serial dilutions (10,102,103,104,105,106, 'undiluted'-109) of cultured H. pylori, and the effects of storage temperature (kits stored at 4°C, 37°C), incubation (aerobic, anaerobic), and contaminants (blood, bile, gastric juice, formalin, saline, water, simethicone) on the sensitivity of each test were determined. Controls used in each reaction were HCl, NaOH, sterile water (pH=7.0), and undiluted culture of H. pylori. All experiments were performed in duplicate, following manufacturer's instructions. Results were interpreted by an experienced clinician who was blinded to the testing conditions. Results: all controls showed appropriate reactions without false positive or negative results. The minimum numbers of H. pylori needed for a positive reaction were 104 for CLO and hpfast and 105 for PyloriTek. Experimental conditions not effecting sensitivity: storage temperature (4°C, 37°C), aerobic, or anaerobic incubation, and presence of contaminants (saline, formalin, water, simethicone, bile+gastric juice, gastric juice+blood, bile+blood) did not effect the sensitivity. The presence of gastric juice and bile decelerated and accelerated the positive reactions respectively, but did not effect the ultimate sensitivity. Experimental conditions effecting sensitivity: mixture of H. pylori, gastric juice, bile, and blood gave a negative reaction with CLO, hpfast, and PyloriTek, even when a pure culture of H. pylori was used. Experimental conditions interfering with interpretation of a positive test: Presence of fresh or clotted blood obscured the color change with the CLO and hpfast and interfered with the interpretation of the results. The results of PyloriTek could be interpreted in the presence of blood. Conclusions: 1) CLO and hpfast require 104 H. pylori and PyloriTek requires 105 H. pylori for a positive reaction. 2) The sensitivities of CLO, hpfast, and PyloriTek for detection of H. pylori were not effected by variations in storage temperature, incubation, or presence of gastric juice, bile, formalin, simethicone, saline, water, bile+gastric juice, gastric juice+blood, bile+blood. 3) CLO, hpfast, and PyloriTek could not detect the presence of H. pylori, even at concentrations of 109, when it was incubated with blood, bile, and gastric juice. 4) Presence of blood can obscure the color change of the CLO and hpfast tests. 5) Biopsies for H. pylori should be taken from an area free of blood in patients with acute bleeding to maximize the performance of commercially available rapid urease tests.
|Original language||English (US)|
|State||Published - 1997|
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