Comparison of immunohistochemical and modified Giemsa stains for demonstration of Helicobacter pylori infection in an African population

ABSTRACT

Modified Giemsa staining has been favoured by many researchers because it is easy to perform but; like many other stains; demonstration of the bacteria depends on its morphology. It has been arged in some research circles that some of the organisms in the gastric mucosa may not be true H.pylori. Immunohisochemical techniques have been developed and make use of anti H.pylori antibody; which reacts; with somatic antigens of the whole bacteria and have been found to correlate well with the presence of the bacteria. Objective: to ascertain the efficacy of modified Giemsa stain in an African setting where H.pylori seems quite prevalent. Study design: A laboratory - based study of two diagnostic tests in which modified Giemsa stain was compared with immunohistochemistry. Methods: A total of 48 consecutive autopsy cases with no upper gastro intestinal diseases had their gastric mucosa stained for demonstration of H.pylori using both modified Giemsa and immunohistochemical staining techniques. Results: Twenty-seven cases of H.pylori were demonstrated by both techniques and 14 cases were not identified by the two staining methods. In 2 cases immunostain could not demonstrate the bacteria but they were identified with modified Giemsa stain while in 5 cases the bacteria were identified by immunostain but not with modified Giemsa stain. The sensitivity of modified Giemsa stain was 85(CI 66.5-98.8) while the specificity was 89(CI 60.4-97.8). The positive predictive value of modified Giemsa stain was 93CI 75 - 98.8) while the negative predictive value was 74(CI 48.6-89.9). The kappa statistic comparing the 2 stains was 0.69 (p-value 0.00001) giving a good agreement between the two tests. Conclusion: With the above results the modified Giemsa stain; which is readily available in most African laboratories; is recommended for diagnosis of H.pylori; a prevalent infection in Africa