Resumo:
The bacterium Helicobacter pylori is an infectious agent linked to the development of
significant gastric pathologies from a public health perspective. The Enzyme-Linked
Immunosorbent Assay (ELISA) is one of the most recommended methods for epidemiological
studies and is also used to investigate virulence factors associated with the bacterium, including the
cagA gene. The performance of serological tests can vary across different populations,
primarily due to the diverse antigenic profiles of bacterial strains, necessitating local validation.
This study aimed to validate serological tests by comparing their results with data obtained from
Polymerase Chain Reaction (PCR), considered the "gold standard" for detecting the cagA
factor, and to determine the prevalence of this factor in bacterial isolates from a population in
the southwestern region of Bahia. The validation assay included 88 individuals, of whom 34
tested positive for the cagA gene using real-time PCR. Regarding the serological analyses, 24
(29.3%) were positive for the cagA factor using the Sunlong cagA-IgG ELISA kit, and 19
(21.6%) were positive using the MyBiosource cagA-IgG kit. After applying a new cutoff point
for both kits, the sensitivity, specificity, and accuracy for the MyBiosource kit were 55.88%,
48.15%, and 51.14%, respectively. For the Sunlong kit, the values were 70.59% sensitivity,
60.42% specificity, and 64.63% accuracy. In conclusion, the commercial tests used did not
perform satisfactorily for serological validation in our population, even after defining a new
cutoff point. Sensitivity remained below 75%, and specificity ranged between 50% and 60%.
The overall prevalence of H. pylori infection in the study was low (34.72%), and the prevalence
of cagA among positives (38.6%) was proportional to the sample size. Therefore, additional
studies using commercial tests from other brands and sample increase are suggested to achieve
better results in the studied population profile.
