Admixture with whole blood does not explain false-negative urease tests

Rapid urease test sensitivity for Helicobacter pylori is reduced in the presence of active upper gastrointestinal bleeding. The aim of this study was to evaluate the in vitro effect of whole blood on rapid urease testing. Urease solution was added to normal saline, and heparinized whole blood both positive and negative for H. pylori antibody. The mixtures were then serially diluted in saline, and/or whole blood and added to three different rapid urease kits. The admixture of urease in H. pylori-seropositive whole blood diluted in either saline or whole blood enhanced performance in both kits fourfold compared with saline alone. No false-negative results were observed in either kit. Seronegative whole blood produced similar results. Undiluted saline or whole blood produced no positive rapid urease tests. Whole blood accelerates the urease reaction in vitro. Neither H. pylori antibody-positive nor -negative whole blood adversely impacted the rapid urease test. False-negative rapid urease test results in upper gastrointestinal bleeding cannot be explained by admixture with whole blood.