25. It was 0.33 in school children with iron deficiency and normal height for age and 0.55 in school children with iron deficiency and low height for age (Fig. 1, Panel B). The sociodemographic or nutritional factors evaluated were not related with evidence of past H. pylori infection (Table 4). Serological tests determined
by antigen-specific enzyme-linked immunosorbent assay, previously validated in Mexican children  and UBT, were utilized for H. pylori detection in this study. At least one of every three school children presented or had presented infection by H. pylori; 26% showed active infection, and 11% showed evidence of past H. pylori infection. More than 70% Small molecule library chemical structure of school children with past or active H. pylori infection were carrying CagA-positive H. pylori strain. These results show a high exposure to the most virulent H. pylori strains in this population. The difference in the estimated frequencies corroborates that each test has a different purpose. UBT identifies active infection, and serological tests determined by ELISA can identify an active or past infection [23, 29]. Furthermore, the results of this study suggest that ID in children with low height for age is associated with active H. pylori infection. Results of this study indicate that the frequency of exposure to H. pylori infection
can be underestimated if the Pirfenidone cell line test to detect CagA is not utilized. Most school children who had evidence of past H. pylori infection were only detected by this test. This could be due to past infection with H. pylori strains carrying CagA, and they could be false-negative cases of
whole-cell H. pylori IgG antibodies. Another alternative is that CagA serology could show cross-reactivity with other antigens and will be less specific. However, this underestimation of previous H. pylori contact has been reported in Mexican children and in adults of other populations where H. pylori serological detection methods have been validated and compared with invasive methods [5, 38] or to CagA antigen antibodies detection by immunoblot . As others suggest, the whole-cell H. pylori and CagA antigens methods detect the immune response to the presence of H. pylori more accurately than the use of either of them alone [28, 33, 38]. As severe gastroduodenal diseases have been associated Niclosamide with H. pylori strains carrying CagA, the determination of this virulence factor could also be of clinical importance [10, 31]. In studies in adults that evaluated the association between H. pylori and noncardiac gastric cancer, it has been reported that it is not only important to identify active infection but also past infection-carrying CagA H. pylori strains. In a meta-analysis about the relationship between CagA seropositivity and gastric cancer, in patients with H. pylori, negative whole-cell antibodies, 37% had seropositivity to CagA whereas in the controls, it was 11%, with an OR of 2.89. Those results show that past infection with CagA H.