Background: 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. Immunohistochemical 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 Giema 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 immunohisto chemical 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 93% CI 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 recommenced` for diagnosis of H.pylori, a prevalent infection in Africa.

Key words: H.pylori, modified Giemsa, immunohistochemical stains. CI –Confidence Interval

H.pylori, formerly Campylobacter pylori, is now accepted as a major cause of chronic active antral gastritis and there is accumulating evidence to incriminate this microbe in the aetiology of duodenal ulcer and gastric carcinoma.^1-2 It is therefore of paramount importance to determine the presence of the organism in surgical pathology specimens in order to manage these two common diseases of the upper gastrointestinal tract. Bacteriological methods would be the ideal confirmatory tests for H.pylori diagnosis but are difficult to perform as they require specialised enrichment media with complicated incubation techniques and characterisation of the microbe is time consuming. Antral biopsy specimens processed for histology would therefore provide an easier and more cost-effective alternative means of diagnosing H.pylori infection. Various special stains have been devised to detect H.pylori in these histological sections but their specificity and sensitivity vary greatly. The haematoxylin and eosin stain, the most frequently used stain in histology, has been found to be the most unreliable.³ The silver stain, though found to be more superior, is quite complicated to carry out and the granular appearance it gives the organisms may be confused with silver precipitate.⁴ Modified Giemsa stain described by Gray et al (1986)⁵ has been favoured by many researchers because of its easiness to perform and availability in most histopathology laboratories.

However all the above-mentioned stains depend on the morphology of the bacterium for identification and it is possible that there are other microbes in the gastric mucosa, which could resemble and become difficult to differentiate from H.pylori. It is also known that H. pylori may demonstrate pleomorphism so that depending on morphology alone may not be reliable for diagnosis. Immunohistochemical 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.⁶ The aim of this study was therefore to ascertain the reliability of modified Giemsa stain in comparison with immunohistochemical technique in diagnosing H.pylori in an African setting where H.pylori seems to be quite prevalent.

Figure 1 shows spiral bacilli in the gastric mucosa

The modified Giemsa stain provided distinctive shape and uniform staining of the bacteria making their identification easy and this was reflected in a high positive predictive value. There were more false negative cases (5 cases) implying that these were probably not detected because of change of morphology from the usual spiral form. H.pylori changes its morphology in culture and during harsh conditions such as antibiotic treatment⁹ and it is possible that after death intragastric changes may also be harsh to the organism. It is therefore correct to assume that with endoscopic biopsy material, the negative predictive value improves.

It is remarkable to find that antibiotic treatment did not influence detection ofH.pylori in this study. However a similar finding was reported by Dooley et al (1989) ⁸ in which antibiotic treatment before the study was a significant promoting factor.

It is most likely thatantibiotics may eradicate other competitive organisms from the stomach leading to over growth of H.plyori.

The study confirms earlier studies that H.pylori causes antral gastritis even in those who are assumed of being asymptomatic of upper gastro intestinal diseases. However it is also possible that in Africa the bacteria may cause no inflammatory response in some individuals as observed in one case in this study. Tsage et al (1996)⁷ also found 9 out of 25 Ethiopian patients with normal antral histology infected with H.pylori and this finding may explain the high seroprevalence of H.pylori accompanied by low prevalence of peptic ulcer and gastric cancer in most parts of Africa. More data on large number of health volunteers in Africa is required to understand the factors, which may enhance tissue response to this bacterium.