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| ORIGINAL ARTICLE |
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| Year : 2021 | Volume
: 27
| Issue : 2 | Page : 153-156 |
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Rapid urease test in the diagnosis of pylori infection
H Thasneem1, KA Sidhic2
1 Department of General Surgery, MES Medical College, Perinthalmanna, Kerala, India
2 Department of Surgery, MES Medical College, Perinthalmanna, Kerala, India
| Date of Submission | 28-Jul-2021 |
| Date of Decision | 04-Sep-2021 |
| Date of Acceptance | 06-Sep-2021 |
| Date of Web Publication | 15-Nov-2021 |
Correspondence Address:
Dr. H Thasneem
Department of General Surgery, MES Medical College, Perinthalmanna - 679 322, Kerala
India
 Source of Support: None, Conflict of Interest: None
DOI: 10.4103/ksj.ksj_38_21
Introduction: Helicobacter pylori is one of the most important causes of the varied spectrum of gastroduodenal diseases. At present, several diagnostic techniques are available to identify infection with H. pylori, including rapid urease test (RUT). Objectives: The aim of this study was to evaluate RUT in the diagnosis of H. pylori infection in patients with upper GI symptoms suspecting peptic ulcer disease. Materials and Methods: It was a prospective study done in department of gastroenterology. Patients of both the sexes in the age group 18–60 years, attending with upper gastrointestinal symptoms suspecting peptic ulcer disease, during a period of 1 year were enrolled in the study. Results: Two ninety-one patients were included, 59% of male, with a mean age of 48.31 ± 15.79 years old. Most common identifiable lesions at endoscopy were antral erosion and gastritis. Significant association was observed between RUT results and biopsy findings. The study proves that positive result of RUT for H. pylori means 5.78 times chance of getting a positive finding in histology. Even though sensitivity of RUT for H. pylori infection was low, specificity was much higher. The sensitivity, specificity and positive and negative predictive values for RUT were, respectively, 41.12%, 88.3%, 71% and 68.47%, which was improved when patients taking proton-pump inhibitors were excluded. Conclusion: RUT positive alone of H. pylori infection is not sufficient as it has a low sensitivity and specificity. A negative RUT result does not fully exclude an active infection hence would need other tests like histology to confirm.
Keywords: Gastroduodenal diseases, Helicobacter pylori, rapid urease test
How to cite this article:
Thasneem H, Sidhic K A. Rapid urease test in the diagnosis of pylori infection. Kerala Surg J 2021;27:153-6 |
| Introduction | |  |
Helicobacter pylori are human pathogens causing chronic gastritis, gastric and duodenal ulcer, gastric carcinoma and dyspepsia. The diagnosis of H. pylori is an essential element in the management of these gastrointestinal pathologies. At present, several diagnostic techniques are available to identify infection with H. pylori. It includes both invasive (rapid urease test [RUT], histology and culture) and noninvasive (urea breath test, 13c-urea blood test, serology and stool antigen test) tests. Routinely we do RUT for the diagnosis of H. pylori infection. As H. pylori treatment may be helpful to prevent future development of GI malignancy, it is important to find out maximum number of cases with H. pylori infection.[1],[2] The aim of the present study was to evaluate the effectiveness of RUT in the diagnosis of H. pylori infection in patients with upper GI symptoms suspecting peptic ulcer disease and to evaluate its sensitivity and specificity in patients with and without usage of proton-pump inhibitor (PPI) and compare with histopathology of gastric specimen collected through endoscopy.
| Materials and Methods | | |
A diagnostic evaluational study was conducted the gastroenterology department of a tertiary hospital in 2018. Patients of both the sexes in the age group 18–60 years, with upper gastrointestinal symptoms suspecting peptic ulcer disease, were enrolled. Sample size was calculated using the formula 4pq/d2 where P = 97% and absolute error 2% 291. Consecutive sampling was done. Patients who gave history of anti H. pylori triple regimen, patients with abnormal coagulation profile or chronic liver disease and those not willing for biopsy were excluded. Approval of the Institutional Ethics Committee was obtained. Informed consent was obtained prior to the endoscopic biopsy procedure. Basic details and short clinical history were recorded. Patients suspecting peptic ulcer disease underwent oesophagogastroduodenoscopy (OGDscopy). The reports of RUT and biopsy were tabulated using a pro forma. Four samples were collected from each patient for histology and the RUT. Two samples for histology: The slides were stained with haematoxylin and eosin and Giemsa; the latter was used to confirm presence or absence of H. pylori. Cases identified with H. pylori in any of the biopsy specimens were considered positive. Two samples were taken for RUT. Sample placed into a medium containing urea and an indicator such as phenol red. Urease produced by H. pylori hydrolyses urea to ammonia, raises the pH of the medium and changes colour of the specimen from yellow (negative) to red (positive). Data entered were analysed using SPSS software. Sensitivity, specificity and predictive values of RUT were calculated using histopathological report of biopsy specimen as gold standard. Chi-square test was used to look for association between history of PPI use and H. pylori infection and gender and H. pylori infection. Relation between age and H. pylori infection was looked for using t'-test. OGDscopy findings were expressed as proportion. Descriptive and inferential statistical analyses were carried out. Results of scalable measurements are presented as mean ± standard deviation, categorical measurements are presented in number and %. Significance was assessed at 5% level of significance. Independent Chi-square/Fisher's exact test was used to find the significance of study parameters on categorical scale between two or more groups.
| Results | | |
The mean age of the 291 patients was 48.31 years ± 15.79, with majority of patients in middle age, as seen in [Table 1]. Males were more 178 (58.8%), compared to females 120 (41.2). The age distribution of the two genders was not statistically significantly different [Table 2].
The OGDscopy findings included gastritis and erosion followed by hiatus hernia and others [Table 3].
The RUT was negative in 222 (76.3%) and positive in 69 (23.7%). Chi-Square test showed a P = 0.212, which is not statistically significant. The histopathological study for H. pylori showed 172 (59.1%) negative and 119 (40.9%) positive. Chi-square test showed a P = 0.795, which was not significant. In our study, the sensitivity of RUT was 41.12%, specificity 88.3%, positive predictive value 71% and negative predictive value 68.47%. Two hundred and twelve out of the 291 patients (72.9%) had been consuming PPI. Chi-square test did not show any statistically significant association between consumption of PPI and H. pylori infection (P = 0.22). There was a statistically significant association between of RUT and histopathology for H. pylori infection (P < 0.001), in both the groups with and without history of PPI intake [Table 4]. | Table 4: Comparison of rapid urease test and histopathology, with and without history of proton-pump inhibitor intake
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The sensitivity and specificity of RUT in patients with history of PPI intake were 30.49% and 90.77%, respectively, whereas the values for the test in patients without history of PPI were 64.86% and 80.96%, respectively [Table 5]. | Table 5: Comparison of sensitivity, specificity, positive predictive value and negative predictive value based on history of proton-pump inhibitor intake
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| Discussion | | |
In the present study, there was no significant difference in age between the biopsy + ve and biopsy negative groups. Males (59%) are predominant in study. Same results were reported in Saudi Arabia,[3] China,[4] Iran[5] and Turkey,[6] although others consider female gender as a risk factor for H. pylori infection.[6] The reason for the possible gender difference in H. pylori prevalence is unclear but may be related to the frequency of eating in restaurants and smoking.
The most common identifiable lesion at endoscopy was gastritis (74.3%). The correlation of endoscopic abnormality with H. pylori infection was statistically highly significant with a P < 0.01, proving endoscopic changes to be a sensitive indicator of H. pylori infection. This is in correlation to the observation laid by Adlekha et al.[7] in which the correlation was statistically significant.
The RUT is the most frequently used test for the diagnosis of H. pylori infection in routine gastrointestinal endoscopy practice. It is extremely valuable because it gives a positive result for H. pylori infection before the patient leaves the endoscopic suite. It is inexpensive, rapid, easy to perform, highly specific and widely available. Based on the activity of the H. pylori urease enzyme, the presence of H. pylori in biopsy specimen converts the urea test reagent to ammonia, leading to an increase in the pH and a colour change on the pH monitor. Histological diagnosis of H. pylori infection is usually reserved for patients with a negative biopsy urease test or when histology was required for another reason such as exclusion of malignancy.
The present study shows sensitivity, specificity and positive and negative predictive values for RUT as 41.12%, 88.37%, 71% and 68.47%, respectively. There is a significant association between RUT results and biopsy findings. The present study proves that positive result of RUT for H. pylori means 5.78 times chance of getting a positive finding in biopsy. The RUT for H. pylori infection sensitivity is low.
In an earlier study, RUT had the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy were 98%, 100%, 100%, 98% and 99%, respectively.[8]
The sensitivity of RUT in those who gave a history of PPI intake is only 30.49% and so it would not be advisable to differ treatment for H. pylori if RUT is negative as nearly 3/4th (69.5%) are false negatives. Ideally, PPI should be discontinued before the endoscopy.[9]
PPIs have strong antigastric secretion effects, in addition to being bacteriostatic against H. pylori. Thus, bacterial density may diminish, particularly in the antrum, but also in the body.[10] For patients who receive PPI therapy, a better approach is to discontinue the PPI before endoscopic biopsy.[11] However, in our practice, patients quite frequently self-medicate. Even referrals from primary care service cannot be discontinuing PPIs for an adequate period before endoscopy. Hence, a negative RUT result does not fully exclude an active infection hence would need other tests like histology to confirm.
The Maastricht IV/Florence Consensus Report for the management of H. pylori infection recommended that in patients treated with PPIs, if possible, the PPIs should be stopped 2 weeks before testing by histology, culture, RUT, urea breath test or stool antigen test.[12]
Previous studies recommend obtaining biopsies of the stomach in patients on PPIs for the diagnosis of H. pylori infection. This is also important in view of the high prevalence of H. pylori in the region. As RUT can miss a low-level infection with H. pylori, a negative test should not be the sole criterion for either absence or cure of H. pylori infection.
It is known that certain endoscopic mucosal features indicate H. pylori infection such as atrophic changes, rugal hyperplasia, oedema, spotty erythema, linear erythema and haemorrhage, amongst others. However, recognition and diagnosis depends on the experience of the endoscopist. Several studies including that by Khaloo et al.(41.8%).[13] and Redeen et al.(43%–53%)[14] have reported a low diagnostic yield. Watanabe et al., however, published a relatively higher diagnostic yield in the H. pylori-uninfected (88.9%) but lower in H. pylori-infected (62.1%) and in the H. pylori-eradicated (55.8%) patients.[15] Our study does not support sole endoscopic diagnosis for H. pylori as a standard of care.
| Conclusion | | |
We found that RUT was positive in 23.7%, whereas in histology, 40.9% of positive results were noted, which shows that 17.2% of cases were false negative with RUT. This explains that when RUT is found to be negative, further evaluation with histology is recommended. The sensitivity of RUT (41%) is decreased in our study because of the fact that most of them had history of PPI intake. Most of the adults in our community would have consumed a PPI. The same can be seen from our study where 212 out of the 291 participants reported history of PPI intake. Anything that reduces bacterial density such as use of antibiotics or PPI may result in false-negative results. One of the most common reasons for false-negative results is the recent use of PPI. It is not clear as to how long one must wait after stopping PPI before the possibility of a false negative result becomes unlikely. The sensitivity of RUT in those who gave history of PPI intake is only 30.49% and so it would be better to do histopathology for H. pylori in those patients with PPI intake and OGD shows features of gastritis.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
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[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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