Our study provides important information about the accuracy of five tests commonly used in clinical practice for the diagnosis of H. pylori infection. Clinicians have a variety of tests to choose from to diagnose H. pylori infection in patients with abdominal symptoms. The data comparing the sensitivity, specificity, and accuracy of each test are incomplete and can be confusing to clinicians. We evaluated the performance of H. pylori tests in a population of Alaskan native adults with a high prevalence of H. pylori infection (53% using the gold standard). The 13C-UBT test accurately diagnosed 91% of persons relative to our gold standard, whereas the serological assay had a reduced accuracy of 81%. Our study suggests that in populations with high rates of sequelae from H. pylori (gastric cancer, duodenal ulcer disease), as well as high H. pylori treatment failure rates, and high reinfection rates after treatment, the 13C-UBT test may be the best non-invasive test option available for longitudinal evaluation of H. pylori infection.
The antibody assay had low specificity and positive predictive value because this test can be positive in persons with a previous successfully treated H. pylori
infection and in those with a current active infection. In this study population of urban Alaska Native adults evaluated by EGD, over 1 in 5 persons were found to have had a treatment for H. pylori
documented in their medical records prior to entering the study. We found some persons who were negative by the gold standard tests for active infection, among whom we were able to document that the presence of anti-HP IgG was associated with previous treatment for H. pylori
. Indeed in this group, persons with a high level anti-HP IgG were close to five times more likely to have been previously treated for H. pylori
compared to those with low levels of anti-HP. Previously published data from this study found that the mean anti-HP IgG level was 0.64 OD units (above the assay’s positive breakpoint) two years after documented successful treatment for H. pylori
] , demonstrating that anti-HP antibodies persist long after eradication. The antibody assay may still be suitable in treatment naïve populations in epidemiological investigations aimed at establishing baseline estimates of H. pylori
prevalence. However, for the clinical purpose of identifying persons with active H. pylori
infection, the antibody test has limited utility, because persons recovered from H. pylori
infection might be mistakenly identified as harboring an active infection. In populations with a high prevalence of, and treatment for H. pylori
infection, this assay is not optimal for use in a “test and treat” strategy in patients with dyspeptic symptoms. Patients identified by elevated antibody levels who are not actively infected may unnecessarily receive additional treatment for H. pylori
We found that the anti-HP OD ≥ 1.1 was associated with male gender and chronic gastritis as determined by histological evaluation. The finding of an association with gastritis has been documented in other studies[13-16
]. Sheu et al[13
] found the titer level of H. pylori
to be associated with antral gastritis but not presence of ulcer, similar to our study. In contrast, Chen et al[17
] did not find an association with antral gastritis when restricting the analysis to H. pylori
positive persons, an analysis similar to ours. Although the serological assay is less accurate in predicting active H. pylori
infection in this Alaska Native population, high levels of anti-HP IgG increased the odds by 4-fold that chronic gastritis will be diagnosed by histology. The lower anti-HP level found in women could be attributable to inadvertent treatment of the H. pylori
infection in the use of metronidazole for treating vaginal infections in women. Indeed, in this study group, women had higher levels of metronidazole use[8
], and higher levels of metronidazole use were associated with lower anti-HP levels (CDC unpublished data).
With a sensitivity and specificity of 93% and 97%, respectively, using the manufacturer’s recommended cut-off point, the 13
C-UBT provided the best non-invasive test for documentation of infection-free status. The accuracy of the test in our population compares well with performance of the UBT (both 13
C-UBT and 14
C-UBT) in other studies[18-20
], and is in contrast to a recent study that found much lower specificity in Spain[21
]. In our study, we found that the accuracy of the 13
C-UBT was > 90% with cut-off points between 2.0 and 4.0 DOB, similar to findings in other reports[22
]. Additionally, we found that the DOB value was positively associated with the amount of H. pylori
present on histological examination. Persons with very high DOB values were over four times more likely to have a high concentration of H. pylori
bacteria than persons with low DOB values, an association documented elsewhere[23-25
]. The association between the concentration of H. pylori
organisms on histology and other pathological outcomes (gastritis, intestinal metaplasia), as well as treatment outcome, is being investigated further.
In summary, in a population in the United States with a high background prevalence of H. pylori, we found that the 13C-UBT test outperforms the serological assay in the detection of active H. pylori infection. The 13C-UBT avoids the problem associated with the serological test of incorrectly identifying persons who have recovered from H. pylori as having active infection. For clinical purposes, in persons with gastrointestinal symptoms in whom an EGD procedure is not planned, the 13C-UBT appears to be useful to rule out or confirm H. pylori infection, and to test for a cure in persons who have been treated for H. pylori infection.