A prospective study on Helicobacter pylori rapid urease test false negativity: is it time for its use in restricted situations?

Background: Rapid urease test (RUT) is a diagnostic tool for Helicobacter pylori (H. pylori) diagnosis, based on the ability of the bacterium to produce urease. Despite it is considered simple, fast, and cheap, some conditions may cause false negativity. Therefore, the aim of this study was to compare RUT with currently recommended tests for H. pylori diagnosis.
Methods: We enrolled consecutive patients who underwent upper endoscopy with histology, RUT, and urea breath test (UBT). Delta over baseline (DOB) >4% was considered positive for UBT. Diagnosis of infection was achieved when at least two tests were positive. The rate of false positivity of RUT was computed, and DOB value in RUT+ versus RUT- was compared by Mann-Whitney Test.
Results: One hundred and sixteen consecutive patients with H. pylori infection were recruited. The male/female ratio was 35/81 and the mean age 45.2±13.1. Twenty-five patients (21.5%) were RUT-, despite being positive at both histology and UBT. On the other hand, in only two patients UBT and histology had discordant results. A full concordance of the three tests was observed in 89 patients (76.7%). DOB, additionally, was significantly higher in RUT+ patients (39.2±24.2%) than RUT- ones (26.3±18.5%; P=0.005).
Conclusions: RUT shows false negativity rate higher than 20%. Moreover, the RUT-negative patients showed a lower DOB at UBT, which is an indirect indicator of intragastric bacterial load. Therefore, it is presumable that H. pylori low amount may be a concurrent cause of false negativity. This study suggests that RUT-based H. pylori detection should be restricted to some specific conditions.