CONCLUSIONES Y RECOMENDACIONES

There are various diagnostic tests for H. pylori which can be broadly classified into invasive and non-invasive tests.¹²¹ Invasive tests utilize endoscopic gastro-duodenal mucosal biopsy samples.

A. The invasive tests for H. pylori are:

i) Histology

Histology of gastric mucosal biopsies has been considered by some to be the gold standard for the detection of H. pylori.¹²² It is however considered to be an imperfect gold standard since its detection of this organism relies upon a number of factors including the site, number, and size of the gastric biopsies, method of staining, and the level of experience of the examining pathologist.¹²²

A significant advantage of histology over other diagnostic methods is the ability to evaluate for pathologic changes associated with H. pylori infection such as inflammation, glandular atrophy, intestinal metaplasia, and malignancy.¹²³ In fact, some have advocated the use of chronic antral gastritis as a surrogate marker for H. pylori infection when the organism is not identified particularly in patients older than 60 years of age.¹²⁴

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Certainly, the absence of chronic gastritis is a potent negative predictor for the presence of H.

pylori infection. As the prevalence and density of H. pylori vary throughout the stomach, particularly in the face of medications that may reduce the density of the organism, multiple biopsies are needed for accurate diagnosis. It is therefore recommended that a minimum of three biopsies be obtained to maximize the diagnostic yield of histology.¹²²

A recent study found that the addition of corpus biopsies to antral biopsies increased the detection of H. pylori infection by approximately 10% when compared with antral biopsies alone.¹²⁵ Although widely available and capable of achieving sensitivity and specificity of greater than 95%, the cost and need for properly trained personnel are limitations of histology in clinical practice.

ii) Rapid Urease Test

The RUT identifies active H. pylori infection through the organism’s urease activity. Gastric biopsies are obtained and placed into an agar gel or on a reaction strip containing urea, a buffer, and a pH-sensitive indicator. In the presence of H. pylori’s urease, urea is metabolized to ammonia and bicarbonate leading to a pH increase in the microenvironment of the organism.

A change in color of the pH sensitive indicator signifies the presence of active infection.

Commercially available kits yield results in one to twenty four hours. There are a number of commercially available RUT kits including the CLO test, HpFast, HUT-test, Pronto Dry, and Pyloritek with overall pre-treatment sensitivities of greater than 90% and specificities of greater than 95%.¹²⁶ Medications that reduce the density and/or urease activity of H. pylori, such as bismuth-containing compounds, antibiotics, or PPIs, can decrease the sensitivity of the RUT by up to 25%.¹²⁶

22 iii) Culture

Culture of gastric mucosal biopsies is another highly specific method for identifying active H.

pylori infection. Conceptually, culture is attractive because it not only provides a means by which to identify infection, but also allows characterization of antimicrobial sensitivities.¹²⁷ Unfortunately, culture is not as sensitive as RUT or histology.^128,129 Furthermore, culturing techniques for H. pylori are demanding and costly and as a consequence, only available in a limited number of clinical laboratories.

iv) Polymerase Chain Reaction (PCR)

PCR is a deoxyribonucleic acid (DNA) amplification technique that utilizes the rapid production of multiple copies of a target DNA sequence to identify H. pylori. This testing method is highly specific and may be more sensitive than other biopsy-based diagnostic techniques.¹³⁰ A recent study found that PCR was able to detect H. pylori in approximately 20% of gastric biopsies with chronic gastritis but no identifiable organisms by histology.¹³¹ PCR also provides a means of identifying mutations associated with antimicrobial resistance.¹³² This method, though, still largely restricted to the research arena, may someday provide a practical and reproducible method for antibiotic sensitivity testing, organism typing, and organism virulence testing.¹³³ v) Fluorescent in situ hybridization

Fluorescent in situ hybridization (FISH) is considered as a rapid and specific detection method in diagnostic microbiology. Fluorescently labeled oligonucleotide probes that target ribosomal RNA are utilized in the FISH technique for direct molecular detection of microorganisms in clinical samples.¹³⁴ FISH is a highly sensitive, cost-effective diagnostic procedure that can deliver results in around 1hour from samples such as smears, body fluids, soft tissue aspirates and formalin-fixed biopsies. By means of FISH with rRNA-targeted fluorescence-labeled

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oligonucleotide probes specific for H. pylori, this organism can be detected in gastric biopsies.¹³⁵ In a comparative study of FISH and histological method for the detection of H. pylori in gastric biopsy samples, the sensitivity and specificity of FISH for the detection of H. pylori were 97.9%

and 100% respectively.¹³⁶ The ability of FISH for determination of antimicrobial resistance is a considerable advantage of this method over histology.¹³⁶

B. The non-invasive tests for H. pylori are:

i) Antibody Tests or Serological tests

Antibody testing relies upon the detection of IgG antibodies specific to H. pylori in serum, whole blood, saliva or urine. IgG antibodies to H. pylori typically become present approximately 21 days after infection and can remain present long after eradication.¹³⁷ Antibodies to H. pylori can be quantitatively assessed using ELISA and latex agglutination techniques or qualitatively assessed using office-based kits. The advantages of the antibody tests are their low cost, widespread availability, and rapid results. Unfortunately, several factors limit the usefulness of antibody testing in clinical practice. A meta-analysis evaluated the performance characteristics of several commercially available quantitative serological assays and found their overall sensitivity and specificity to be 85% and 79% respectively, with no differences between the different assays. Antibody tests are of little benefit in documenting eradication of infection as results can remain positive for years following successful cure of the infection.¹³⁷

ii) Urea Breath Tests

The UBT, like the RUT, identifies active H. pylori infection by way of the organism’s urease activity. In the presence of H. pylori, the ingestion of urea, labeled with the non-radioactive isotope ¹³C or the radioactive isotope ¹⁴C, results in production of labeled CO2, which can be quantified in expired breath.^138-141 Although the amount of radiation in the ¹⁴C UBT is less than

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the daily background radiation exposure, the ¹³C test is preferred in children and pregnant females.^138,139

Overall, the performance characteristics of both tests are similar with sensitivity and specificity typically exceeding 95% in most studies.^138,139 Test reproducibility has been found to be excellent.¹⁴⁰ The UBT also provides an accurate means of post-treatment testing.^141-144

Most tests utilize a citrate test meal (50-75 mg), which is administered before the labeled urea.¹³⁸ A urease blood test, which relies upon the detection of labeled bicarbonate in a blood sample, also reliably identifies active H. pylori infection before and after treatment.^145,146 As the non-endoscopic urease tests rely upon the identification of H. pylori’s robust urease activity, test sensitivity is decreased by medications that reduce organism density or urease activity, including bismuth containing compounds, antibiotics, and PPIs.

It is currently recommended that bismuth and antibiotics be withheld for at least 28 days and a PPI for 7-14 days prior to the UBT.¹⁴⁷ It is controversial whether H2RAs affect the sensitivity of the UBT though many laboratories recommend withholding these drugs for 24-48hours before the UBT.^148,149 Antacids do not appear to affect the accuracy of the UBT.¹⁵⁰

iii) Faecal Antigen Test

The faecal antigen test (FAT) identifies H. pylori antigen in the stool by enzyme immunoassay with the use of polyclonal anti-H. pylori antibody. Monoclonal anti-H. pylori antibody has also been used in the detection of H. pylori antigen in stool.^151-153 Both tests detect the bacterial antigen(s) in the stool which is suggestive of ongoing infection. Thus, they can be used to screen for infection and as a means of establishing cure following therapy.

A recent systematic reviewwhich reported performance characteristics of the FAT before and after eradication therapy demonstrated excellent sensitivity, specificity, positive predictive

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values (PPV) and negative predictive values (NPV) for the polyclonal test before treatment, while sensitivity and PPV were less satisfactory after treatment.¹³⁸ On the other hand, the monoclonal test yielded sensitivity, specificity, and predictive values greater than 90% before and after treatment.

The precise explanations for the differences in accuracy between the polyclonal and monoclonal tests remain unclear but may have to do with the need for intra-peritoneal injection of H. pylori antigens into rabbits to produce antibodies for the polyclonal assay.¹³⁸ The FAT has been approved by the USA Food and Drug Administration (FDA) and endorsed by the European

“Maastricht 2–2000 Consensus Report” as an alternative means of establishing H. pylori cure to urea breath testing.⁶ Recent studies indicate that the FAT may be effective in confirming eradication as early as 14 days after treatment.^154,155 However, there is evidence to suggest that the FAT should be done more than 4 weeks and perhaps as long as 8-12 weeks after treatment of H. pylori.¹³⁸

The endoscopy based methods however offer the added advantage of enabling the evaluation of the upper GI tract of dyspeptic patients for the presence of mucosal lesions. This influences the management of these patients. Moreover, dyspeptic patients who are aged 55 years or more, or those with alarm features (which include bleeding, anaemia, early satiety, anorexia, unexplained weight loss (>10% body weight), progressive dysphagia, odynophagia, persistent vomiting, a family history of GI cancer, previous oesophago-gastric malignancy, previous documented peptic ulcer, lymphadenopathy, or an abdominal mass) should undergo prompt upper GI endoscopy to rule out PUD, oesophago-gastric malignancy, and other rare upper GI tract disease.¹

26 2.8.7 Prevalence studies on H. pylori infection

The prevalence of H. pylori has been studied among different populations in Nigeria, particularly among patients with dyspepsia. Two different prevalence rates were observed by different group of authors who studied the prevalence of H. pylori among dyspeptic patients in the North-Eastern region of Nigeria.^156,157 A prevalence rate of 78.5% was observed in a study of three hundred and thirty (330) dyspeptic patients in Maiduguri using histology of gastric antral biopsies.¹⁵⁶ _ENREF_157The other study from the region was also from Maiduguri, albeit over a decade earlier, with a rate of 85% obtained in a random serological survey of two hundred and sixty eight (268) subjects using IgG antibodies to H. pylori.¹⁵⁷ The use of different methods of H.

pylori detection (serology used by Holcombe and his colleagues as against histology of gastric biopsies used by Mustapha and his colleagues) and the difference in the period in which these studies were done (1992 vs 2007) may account for the different prevalence rates obtained from the same study centre.

In North-Western Nigeria, a group of authors using histology of antral biopsies for H. pylori detection, found a prevalence of 81% among dyspeptic patients in Kano.¹⁵⁸ In Ile-Ife which is located in the South-Western region of Nigeria, a prevalence rate of 73% was obtained in a study in which the detection of H. pylori in gastric mucosal biopsies was done by combining the Campylobacter-Like Organism (CLO) test with histology.¹⁴ In Ibadan, however, in a study where detection of IgG antibodies to H. pylori was used in evaluating the presence of this organism, a prevalence rate of 94.5% was obtained.¹³ The higher rate observed in the latter study is not surprising because the persistence of anti-H. pylori IgG antibodies in the serum long after clearance of the organism from the stomach make serological tests discriminate poorly between current and past infection with the organism.

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The prevalence rates obtained from these studies reveal that, generally, there is a high prevalence of this organism in Nigeria. These rates, however, appear to differ between and within the regions in the country. These observed differences can be attributed to factors such as differences in the methods used in H. pylori detection, the sample sizes used, the socio-demographic characteristics of the population studied (particularly the age of subjects enrolled), the geographical location and the period of time during which these studies were carried out.

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CHAPTER THREE AIM AND OBJECTIVES AIM

To determine the prevalence of H. pylori infection and the gross endoscopic findings among patients with dyspepsia in UITH, Ilorin.

OBJECTIVES

1) To determine the prevalence of H. pylori infection among the dyspeptic patients.

2) To identify the association between H. pylori and the gross endoscopic findings.

3) To determine the relationship between H. pylori infection and the findings on histology.

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CHAPTER FOUR

SUBJECTS, MATERIALS AND METHODS 4.1 STUDY SITE AND DESIGN

This was a hospital based cross-sectional observational study that was carried out at the Gastroenterology clinic and the Endoscopy suite of the University of Ilorin Teaching Hospital (UITH), Ilorin from April 2012 to December 2012. The hospital is a tertiary health institution which is located in the North-Central region of the country and provides services to patients from the whole of Kwara State and parts of Kogi, Niger, Ekiti, Oyo and Osun States.