Date of Award
2021
Document Type
Dissertation
Degree Name
Master of Medicine (MMed)
First Supervisor/Advisor
Dr. Gunturu Revathi
Second Supervisor/Advisor
Dr. Allan Njau
Third Supervisor/Advisor
Dr. Evariste Tshibangu
Department
Pathology (East Africa)
Abstract
Background: Helicobacter pylori infects approximately half of the world’s population. The main virulence factors, CagA and VacA, are associated with chronic gastritis and cancer. Notable geographic and temporal variations in the prevalence and genotypes of H. pylori in relation to gastric pathologies have been observed, however, their significance and trends in African populations is scantly described. The aim of this study was to investigate the association of H. pylori and its respective CagA and VacA genotypes with gastric adenocarcinoma and to describe the trends of H. pylori genotypes over the last 8 years (2012-2019).
Materials and Methods: A total of 286 samples comprising 143 gastric cancer cases and a corresponding number of matched benign controls, from three main cities in Kenya, between 2012 and 2019 were included. Histologic re-evaluation was performed, and the presence of H. pylori, CagA and VacA genotypes determined using Polymerase Chain Reaction (PCR). Distribution of H. pylori and its genotypes was presented in proportions. The results for each of the target genes were compared using 2*2 contingency tables. To determine association, univariate analysis was conducted using a Wilcoxon rank sum test for continuous variables, and a Chi squared test or Fishers Exact test for categorical data.
Results: Compared to benign controls, VacA m1 and VacA s1 H. pylori genotypes in gastric adenocarcinoma were found at a higher frequency, (odds ratio of 1.59 and 2.90, (p=0.501 and p=0.068 respectively). The VacA s1m1 genotype was more likely to be associated with gastric adenocarcinoma, (OR=2.68 [CI 95%: 0.83-8.65]; p=0.108). The VacA s2m2 genotype was significantly associated with a reduced probability of gastric adenocarcinoma (OR=0.23 [CI 95%: 0.07-0.78]; p=0.031). No significant association between the CagA and gastric adenocarcinoma was observed (OR=0.69 [CI 95%: 0.25-1.87]; p=0.628).
Conclusion: Over the eight years of the study, there was an increase in all genotypes of H. pylori. Although no predominant genotype was noted, there was significant year-to-year variation with VacA s1 and VacA s2 showing the greatest variation. Intestinal metaplasia and atrophic gastritis did not appear to be significant in this population, however, VacA s1m1 and VacA s2m2 were associated with increased and reduced risk of gastric cancer respectively.
Recommended Citation
Njenga, P. W. (2021). Association of helicobacter pylori caga and vaca genotypes with gastric adenocarcinoma in Kenya (Unpublished master's dissertation). Aga Khan University, East Africa.