Objectives: Several methods are used to detect Helicobacter pylori (HP) infection. However, few reports have evaluated the accuracy of each method and compared the grade of HP infection with the severity of histological changes. HP infection was evaluated semiquantitatively in relation to the severity of gastritis, and the sensitivity, specificity, and accuracy of several methods to detect HP infection were compared.
Methods: Biopsy specimens, obtained from a total of 64 patients who underwent endoscopy for evaluation of gastroduodenal diseases, were studied using a rapid urease test, culture, and histological assessment. An immunohistochemical method was used as the gold standard and graded according to the number of individual bacteria seen, as follows: 0 = 0; 1+ = <10; 2+ = 10-29; 3+ = 30-99; 4+ = >100. The severity of gastritis was evaluated histologically in each specimen and compared with the grade of HP infection.
Results: The rapid urease test had a sensitivity of 53%, specificity of 100%, and accuracy of 73%. The culture method had a sensitivity of 75%, specificity of 100%, and accuracy of 86%. Sensitivities of the rapid urease test and the culture method decreased in a positive correlation with the decrease in total number of HP bacteria counted. Using the rapid urease test, sensitivity was <30% when the grade of HP infection was < or =2+, whereas 100% sensitivity was obtained when the grade of HP infection was 4+. On the other hand, sensitivity of the culture method remained between 80% and 90% when HP infection was > or =2+. The severity of gastritis determined with Rauws scores increased in a positive correlation with the grade of HP infection as evaluated by immunohistochemical stain.
Conclusions: The rapid urease test and culture of HP may result in false-negative tests for a mild infection, although they had high sensitivity and specificity for moderate to severe infection. Immunohistochemical stain provides a reliable semiquantitative diagnosis of HP infection and a positive correlation with histological changes. Clinicians should be aware of the characteristics of each method to detect HP infection and select the appropriate one(s) for their purposes.