Will saliva test be a good method to detect Helicobacter pylori in H. pylori -infected patients?

In developing a noninvasive method of detecting Helicobacter pylori from saliva, there are several issues that require clarification. First, is the presence of H. pylori in dental plaque equal to the presence of H. pylori in the stomach? In earlier studies, the prevalence of H. pylori in dental plaque ranged from 0% to 100% in patients positive for gastric H. pylori. This wide variation may be explained by the use of different sampling procedures to detect the bacterium in dental plaque [urease tests, polymerase chain reaction (PCR) techniques, immunoassays, cytology, and culture]. The prevalence rate reported in studies using urease tests was higher than with other techniques. The lowest rate of detection has been reported with microbial culture (usually < 20%), which has been attributed to the existence of H. pylori in the metabolically active but unculturable coccoid form in dental plaque. The use of urease tests for the detection of H. pylori in dental plaque has been debated. This controversy results from the fact that although H. pylori is the only urease-positive microorganism that resides in the stomach, many urease-positive bacterial species, such as Haemophilus, Streptococcus, and Actinomyces species, may be detected as part of the normal oral flora. However, it has been reported that only H. pylori produces large amounts of urease, such that a positive urease test can occur within 20 minutes, while other urease-producing bacteria are not positive within 1 hour. The PCR technique for detection of H. pylori provides the advantage of detecting even small numbers of the target species and detecting the target DNA in spite of the viability of the bacteria. The results of utilizing PCR techniques have been variable, ranging from 0% to 100%. Second, does the presence of H. pylori in saliva match the presence of H. pylori in the stomach? The detection rate in saliva was generally less than in dental plaque (usually < 50%). However, the prevalence rate was even lower in studies in which culture was used for detecting H. pylori compared with studies using PCR. This may be because dental plaque is a biofilm, which allows the bacteria to adhere to solid surfaces, and the continuous flow of saliva may result in a reduction in bacterial load, making detection difficult. As with dental plaque, researchers have differed in