Yemenis pinpoint most precise H. pylori diagnosis test

Yemeni researchers have standardized a PCR test that diagnoses Helicobacter pylori infections more accurately than existing methods¹.

H. pylori, a bacterium present in the stomachs of more than half the world’s population, is a well-known risk factor for stomach ulcers, chronic active gastritis, and several different types of stomach cancer.  

Its prevalence is significantly higher in developing than in developed countries (around 80% and 30%, respectively), and differs markedly between countries in the same region. In the Middle East, for example, 80% of Egyptians are infected, compared with 50% of Saudi Arabians.

H. pylori can be detected non-invasively by blood tests, breath tests and stool sampling, or by tissue sampling followed by biochemical, culture-based or molecular assays, depending on the resources available. The most accurate method is the rapid urease test, where the bacterial enzyme urease, which H. pylori uses to break down urea into ammonia and carbon dioxide, is detected in tissue samples. As yet, however, there is no gold standard for diagnosing H. pylori infection.

Recently, there has been growing interest in using quantitative PCR (q-PCR) to diagnose H. pylori infection. However, the assay remains largely unstandardized. A new test developed by Nezar Al-hebshi and his team at the University of Science and Technology in Sana’a uses a commercial real-time quantitative PCR (q-PCR) kit to detect the presence of the ureA gene, which encodes the urease enzyme, in samples collected.

The researchers collected 76 stomach biopsy specimens from patients undergoing endoscopies, and examined them with their own test as well as two established ones — the rapid urease test, and a bacterial cell culture method used to see if bacteria are present in blood or stool samples.

According to their results, the q-PCR test was marginally more accurate than the rapid urease test, with a sensitivity and selectivity of 94.9% and of 94.6%, respectively. It may therefore be the most accurate method for diagnosing H. pylori infections, but the rapid urease test costs less and is faster and easier to conduct.

“Q-PCR assays are known for being very sensitive,” says Al-hebshi. “In our study, samples with low bacterial counts detected only by q-PCR were considered as false positives, the assumption being that such low counts do not represent true infection.”

“However, the possibility remains that they do represent true infections that simply cannot be detected by routinely used assays. We plan to assess the reproducibility of the assay [and] investigate whether or not low bacterial counts detected only by q-PCR represent true infection.” 

1. Al-Moayad, E. E., Alghalibi, S. M., Al-Shamahy, H. A., Nasher, A. T. & Al-hebshi, N. N. Normalized real-time PCR for diagnosis of
H. pylori infection. Qatar Med. J. 2014, 19 (2014) | article