Helicobacter pylori Prevalence and CagA Status Among Children in Two Counties of China with High and Low Risks of Gastric Cancer

Abstract

BACKGROUND: Studies in adult populations in selected countries with widely varying rates of gastric cancer have shown a weak correlation between gastric cancer mortality rates and the prevalence of CagA+ strains of H. pylori. However, only limited data are available in ethnically homogenous populations with varying rates in the same region.

METHODS; We compared the prevalence of H. pylori in general and of CagA+ strains in particular among children in Shandong Province, China in areas at high (Linqu County) and low risk (Cangshan County) of gastric cancer. H. pylori status among children aged 3 to 12 years was determined by ¹³C-UBT, and CagA status was determined by enzyme-linked immunosorbent assay (ELISA). Because of the difficulty in obtaining blood from young children aged 3 to 4 years and from some children aged 5 years, CagA status was determined among part of children 5 years old and children 6 to 12 years old.

RESULTS; Among 98 children aged 3 to 12 years in Linqu, 68 (69.4%) was H. pylori-positive, as compared with 29 (28.7%) among 101 children in Cangshan. Among children positive for ¹³C-UBT, the proportion of the CagA+ strains were identified was 46 (88.5%) of 52 in Linqu and 13 (81.3%) of 16 in Cangshan, respectively.

CONCLUSIONS: The prevalence of H. pylori was nearly three times higher among children in Linqu than in Cangshan, which may contribute to the large differential in gastric cancer rates for two neighboring populations in Shandong Province.

Introduction

The presence of CagA+ strains of Helicobacter pylori (H. pylori) in the human stomach may be associated with an increased risk for chronic atrophic gastritis and, possibly, gastric cancer 1, 2, 3, 4. However, cross-sectional studies in adult populations in five countries with varying mortality rates for gastric cancer yielded only a weak association of gastric cancer and mortality rates with the prevalence of CagA+ strains of H. pylori (5). Only limited data are available on ethnically homogeneous populations in a particular region with varying rates, particularly with respect to early-life infection, which is suspected of playing an important initiating role in populations at high risk for gastric cancer 1, 2, 6. Linqu County in Shandong Province, China has one of the highest gastric cancer mortality rates in the world (70/10⁵ males and 25/10⁵ females per year), along with a high prevalence of precancerous lesions, including intestinal metaplasia (7). In contrast, Cangshan County, less than 200 miles away, has gastric cancer mortality rates that are much lower (5/10⁵ males and 3/10⁵ females per year), and the prevalence of intestinal metaplasia also is low (7). Linqu and Cangshan counties are both rural areas with a population of approximately 1 million in Shandong Province. The two counties have similarly ethnic, cultural, and socioeconomic characteristics except that Cangshan County is one of the world's leading agricultural producers of garlic (garlic production: 900,000 tons per year or 806 kg per person per year in 1996). Previously, we found that the prevalence of H. pylori infection was 73.7% among adults aged 35 to 64 in Linqu County, significantly higher than that in Cangshan County (59.9%) (8). One limitation of the previous study was that we had no information on the prevalence of H. pylori among children in the two areas, because H. pylori infection in the childhood might have an important role in the risk of gastric cancer and its precursor. In this study, we compared the prevalence of H. pylori in general and of CagA+ strains in particular, among children aged 3 to 12 in these two counties.