Logo-ajcmi
Submitted: 11 Jan 2022
Revised: 23 Apr 2022
Accepted: 08 May 2022
First published online: 29 Jun 2022
EndNote EndNote

(Enw Format - Win & Mac)

BibTeX BibTeX

(Bib Format - Win & Mac)

Bookends Bookends

(Ris Format - Mac only)

EasyBib EasyBib

(Ris Format - Win & Mac)

Medlars Medlars

(Txt Format - Win & Mac)

Mendeley Web Mendeley Web
Mendeley Mendeley

(Ris Format - Win & Mac)

Papers Papers

(Ris Format - Win & Mac)

ProCite ProCite

(Ris Format - Win & Mac)

Reference Manager Reference Manager

(Ris Format - Win only)

Refworks Refworks

(Refworks Format - Win & Mac)

Zotero Zotero

(Ris Format - FireFox Plugin)

Abstract View: 1307
PDF Download: 674
Full Text View: 46
Avicenna Journal of Clinical Microbiology and Infection. 9(2):55-62. doi: 10.34172/ajcmi.2022.09

Original Article

Determination of Helicobacter Pylori Infection Prevalence by Non-invasive Methods

Mohammad Javad Gharavi 1 ORCID logo, Javad Zarei 2, Parisa Roshani Asl 3, Zahra Yazdanyar 4, Masoud Sharif 4, Niloufar Rashidi 1, * ORCID logo

Author information:
1Department of Medical Laboratory Sciences, Faculty of Allied Medicine, Iran University of Medical Sciences, Tehran, Iran
2Department of Health Information Technology, School of Allied Medical Sciences, Ahvaz Jundishapur University of Medical Sciences, Ahvaz, Iran
3Department of Microbiology, Faculty of Basic Sciences, Shahrekord Branch, Islamic Azad University, Shahrekord, Iran
4Department of Medical Laboratory Sciences, Faculty of Allied Medicine, Tehran University of Medical Sciences, Tehran, Iran

*Corresponding author: Niloufar Rashidi, Department of Medical Laboratory Sciences, Faculty of Allied Medicine, Iran University of Medical Sciences, Tehran, Iran. Email: ni.rashidi@gmail.com

Abstract

Background: Helicobacter pylori (H. pylori) is identified as the most frequent agent of bacterial infections in humans which can cause various gastrointestinal diseases. This pathogen has infected approximately half of the world’s population, and its outbreak has varied across different regions. The purpose of this study was to estimate the H. pylori infection prevalence amongst patients in Fardis county, Alborz province, Iran, using noninvasive methods.

Methods: A total of 5677 patients were analyzed from September 2020 to October 2021 to detect H. pylori by the use of enzyme-linked immunosorbent assay (ELISA) IgG, IgA, and IgM tests, stool antigen test (SAT), and urea breath test (UBT).

Results: Of 5677 patients, 3486 (61.4%) were female and 2191 (38.6%) were male with the mean age of 38.82 ± 18.289 years old. The overall rate of H. pylori infection positive was 31.46%, and the serological tests were the most prescribed types of tests. The IgG test and then SAT detected the most positive cases. Further, the infection rate was significantly associated with age. Except for the case of IgM, which was higher in females compared to males, no significant difference was found between gender and bacteria outbreak.

Conclusions: This study indicated a decline in H. pylori infection prevalence compared with the prior survey conducted at this center. However, its rate amongst the patients referring to Fardis laboratory is still high.

Keywords: Helicobacter pylori, Enzyme-linked immunosorbent assay, IgA, IgM, IgG, Stool antigen test, Urea breath test

Copyright and License Information

© 2022 The Author(s); Published by Hamadan University of Medical Sciences.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium provided the original work is properly cited.

Please cite this article as follows: Gharavi MJ, Zarei J, Roshani Asl P, Yazdanyar Z, Sharif M, Rashidi N. Determination of helicobacter pylori infection prevalence by non-invasive methods. Avicenna J Clin Microbiol Infect. 2022; 9(2):55-62. doi:10.34172/ajcmi.2022.09


Background

Helicobacter pylori is recognized as the most prevalent pathogen responsible for chronic bacterial infection in humans and infects approximately half of the population around the world (1,2). H. pylori is a gram-negative, microaerophilic, spiral-shaped, and flagellated bacterium that is frequently found in the stomach (3,4). It contains microbiological features including urease, catalase, and oxidase activity that are crucial for facilitating the survival of the pathogen and colonization in the adverse acidic gastric environment (5).

Helicobacter pylori infection is extensively identified as the main cause of many gastro-intestinal diseases such as duodenal ulcer, peptic ulcer, chronic gastritis, mucosa-associated lymphoid tissue lymphoma, and especially gastric cancer (6,7). Moreover, several extra-gastric diseases like ischemic heart diseases, type 2 diabetes mellitus, and anemia are the outcomes of contamination with this microorganism (8). Not limited to gastric cancer, H. pylori infection also plays a major role in various cancer incidences including pancreatic and lung cancer (9). Consequently, the International Agency for Research on Cancer of the World Health Organization has classified H. pylori as a class I carcinogen in humans (10,11). Although the exact mode of bacterial transmission has not been clearly identified up to now, the scientific literature proposed that the infection transmission occurs person-to-person mainly through oral-oral, fecal-oral, and gastro-oral ways (12).

The H. pylori infection distribution varies all over the world, and it is influenced by socioeconomic conditions along with sanitation (13). In fact, in developing countries particularly those with substandard socioeconomic status, the H. pylori contamination rate is more than 80%; however, this rate is less than 40% in developed countries (14,15).

Helicobacter pylori contamination commonly occurs at earlier ages. Only about 10% of the people infected with this bacterium exhibit clinical manifestations, while 90% of the patients are asymptomatic, and this infection would continue for all their life if the appropriate treatments were not going to be provided to patients (16). It has been demonstrated that H. pylori elimination can improve the consequences of those diseases caused by this bacterium and restitute a healthy microbiome in the stomach and intestines (17). Therefore, knowledge of the H. pylori situation through accurate diagnostic procedures is a significant step for effective management of its remedy. Nowadays, numerous methods are available for detecting the H. pylori infections, which are classified as invasive (e.g.,, endoscopy and endoscopic biopsy for histopathology, culture, and rapid urease test) and non-invasive (e.g.,, stool antigen test (SAT), urea breath test (UBT), and serological tests) tests (18). It is also noteworthy to state that none of these tests alone is a definite method or a gold standard for detecting the H. pylori infection, and selection of the optimal technique depends on different variables, including the H. pylori spread in each area, patient’s age, clinical outline, and test availability. However, the non-invasive methods are considered the preferred and recommended methods for the H. pylori infection screening in investigations with large populations (19,20). The basis of these tests is the tracing of the existence of bacterial enzymes, antigens, antibodies, or DNA sequences (21).

Given the above-mentioned discussions, investigating the spread rate of H. pylori in a geographical area is very important, leading to improvement in the clinical practice, development in prevention, and control of measures in that region. Therefore, this study aimed to determine the H. pylori infection prevalence using non-invasive methods.


Materials and Methods

Study Design and Population

This descriptive cross-sectional study was conducted to determine the H. pylori infection prevalence in patients suspected of being infected by H. pylori who were referred to the referral laboratory of Fardis county, Alborz province, Iran. A total of 5677 patients were examined from September 2020 to October 2021.

Inclusion/Exclusion Criteria

The only inclusion criterion to this study was living in Fardis, Alborz province, while exclusion criteria were history of H. pylori eradication therapy, use of any medication such as antibiotics, proton pump inhibitors, non-steroidal anti-inflammatory drugs, or H2-receptor antagonists within the past 30 days.

Serological Tests

About 5 mL of venous blood was obtained from each patient under sterile conditions and was transferred to a vacutainer tube without anticoagulant. These collected samples were placed at room temperature for 45 minutes to clot. After that, the test tubes were centrifuged at 3500 × g for serum isolation for 10 minutes. Afterward, the harvested serum was processed for H. pylori antibodies. Anti-H. pylori IgA, IgM, and IgG detection for each sera sample was accomplished using enzyme-linked immunosorbent assay (ELISA) kit (Pishtaz Teb Co, Iran) with a sensitivity of 95% and specificity of 98% according to the manufacturer’s instructions. Any titer above 12 units was considered positive for IgA, IgM, and IgG (negative > 8, equivocal 8 to 12, and positive >12 U).

Stool Antigen Test

Stool samples were gathered from each participant and stored at -20°C until the time of analysis. The examination of stool samples for detecting H. pylori antigen was performed using ELISA by applying a commercially available kit (Astra SRL, Via Ciro Menotti, Milano, and Italy). At first, a small segment of the stool specimen was transferred to the sample diluent vial and mixed thoroughly. After that, the diluted stool sample was added to antibody-coated micro wells and was incubated at room temperature. In the next step, H. pylori-specific monoclonal antibodies conjugated to horseradish peroxidase were added and incubated again. After that, unbound material was removed by washing, and peroxidase was added. Accordingly, the absorbance was read at 450 nm using a spectrophotometer, a visible blue reaction indicated the H. pylori presence. The sensitivity, specificity, and accuracy of this kit have been validated to be 100%, 96.6%, and 96.7%, respectively.

Urea Breath Test

The UBT was performed using a commercial kit (Kibion, Sweden). After collecting a baseline breath sample, each patient received C-14 urea as a tablet that was dissolvable in water. Another breath sample was collected 30 minutes after the test solution administration. After that, the samples were measured for liberating CO2-14, which was detected by the Gamma counter apparatus. The urea hydrolysis with the rate of 50 counts/ minutes or higher was considered positive for H. pylori infection.

Data Analysis

The collected data were analyzed by using SPSS version 22 and by applying descriptive statistics (frequency, frequency percent, average, and standard deviation), one-way ANOVA, Independent samples t test, and the chi-square statistical tests. In addition, the confidence interval for statistical tests was considered significant at 0.95.


Results

Descriptive Information of the Study Population (the Patients With Suspected Helicobacter pylori Infection)

A total of 5677 subjects containing 3486 (61.4%) females and 2191 (38.6%) males were analyzed from September 2020 to October 2021. The mean age of subjects was 38.82 ± 18.289 years old within the age range of 1-92. Moreover, the participants mostly belonged to the age group of 31 to 45 years old (32.3%). The baseline demographic characteristics of participants are presented in Table 1.


Table 1. Demographic Characters of the Study Population
Age Group Gender Total
Male Female
Age (y)
≤5 122 111 233 (4.1%)
6-15 214 279 493 (8.7%)
16-30 379 670 1049 (18.5%)
31-45 760 1073 1833 (32.3%)
46-60 449 896 1345 (23.7%)
61-75 221 394 615 (10.8%)
>75 46 63 109 (1.9%)
Total 2191 3486 5677

Diagnostic Tests

Detecting the bacterium for each one of the patients was accomplished using the method prescribed by their physician. For some patients, more than one test was performed. Totally, 8060 experiments were done on these patients. The highest performed diagnostic test was the anti-H. pylori IgA test (2539). Other experiments included IgG (2159), SAT (1964), IgM (1257), and UBT (141).

The Results of Helicobacter pylori IgG Antibody Test

The H. pylori IgG antibody test was performed on 2159 patients. The mean IgG antibody titer in these patients was 1.938 ± 2.179, ranging from 0.1 to 11.5. The test results were positive for 1147 (53.1%) individuals with a mean of 2.282 ± 3.218 antibody titer (Table 2). There was no statistically significant association between gender and the level of IgG antibody (P value = 0.802, 0.873). However, there was a significant association between the age of the patients and the level of H. pylori IgG antibody (P value = 0.00). Accordingly, the number of seropositive IgG cases was higher in those patients aged above 30 years old, and the mean IgG level was also higher among the group aged 31-75 years old (Table 2).


Table 2. Helicobacter Pylori IgG Test Results
Criteria Helicobacter pylori IgG Test Results N
Negative
(>0.80)
Equivocal
(0.80–0.89)
Positive
(>0.89)
Gender Male 368(43.6%) 36(4.3%) 441 (52.2%) 845
Female 554(42.2%) 54 (4.1%) 706 (53.7%) 1314
Age group ≤5 85 2 11 98
6-15 171 12 32 215
16-30 183 19 208 410
31-45 219 29 424 672
46-60 175 14 310 499
61-75 81 11 139 231
>75 8 3 23 34
Total 922 (42.7%) 90 (4.2%) 1147 (53.1%) 2159

The Results of the Helicobacter pylori IgA Antibody Test

The H. pylori IgA antibody test was performed on 2539 patients. As indicated in Table 3, the average IgA antibody titer in these patients was 2.088 ± 2.285 ranging within 0.1-12.3. Furthermore, the test result was positive for 2 (0.2%) patients, and the mean antibody titer in these individuals was 12.1 ± 0.282. Further statistical analysis indicated no significant association between sex and IgA level (P value = 0.129, 0.793). However, in individuals aged over 31 years old, the number of equivocal cases for IgA antibody test was greater than others, and the IgA level average was also higher in the groups aged 31-75 years old. It means that there was a statistically significant association between age and the level of IgA antibody (P value = 0.00).


Table 3. Helicobacter pylori IgA Test Results
Criteria Helicobacter pylori IgA Test Results N
Negative
(>0.90 >)
Equivocal
(0.90–11.0)
Positive
(>11.0)
Gender Male 445(46.8%) 516(53.1%) 1(0.1%) 962
Female 715(45.6%) 851(24.4%) 1(0.1%) 1576
Age group ≤5 83 11 - 94
6-15 186 32 - 218
16-30 267 210 1 478
31-45 276 489 1 766
46-60 215 400 - 615
61-75 114 193 - 307
>75 29 32 - 61
Total 1170 (46.1%) 1367 (53.8%) 2 (0.1%) 2539

The Results of the Helicobacter pylori IgM Antibody Test

The results of this test which was performed on 1256 patients are reported in Table 4. According to the obtained data, the average level of IgM antibody was 2.259 ± 3.954, ranging from 0.1 to 25.7. The test was considered positive for 14 (1.1%) cases with an average antibody titer of 4.862 ± 16.136. Although there was no statistically significant association between gender and the result of the H. pylori IgM antibody test (P value = 0.827), there was a significant association between gender and IgM level (P value = 0.00), and the average level of the H. pylori IgM antibody in women was higher compared to men (4.207 to 3.551). Furthermore, there was a significant relationship between the age of the patients and IgM test results (P value = 0.00), and the number of positive and equivocal cases was higher in the age group between 30-45 years old. Along with that, the mean IgM level was higher in groups aged 16-30, 6-15, and 31-45 years old (4.258, 4.165, and 4.098), respectively, indicating a significant relationship between age and mean IgM level (P = 0.004).


Table 4. Helicobacter pylori IgM Test Results
Criteria Helicobacter pylori IgM Test Results N
Negative
(>0.90)
Equivocal
(0.90–11.0)
Positive
(>11.0)
Gender Male - 479(99%) 5(1%) 484
Female - 763(98.8%) 9(1.2%) 772
Age group ≤5 - 79 - 79
6-15 - 138 1 139
16-30 - 231 1 232
31-45 - 391 7 398
46-60 - 267 1 268
61-75 - 115 3 118
>75 - 21 1 22
Total 0 (0%) 1242 (98.9%) 12 (1.1%) 1256

SAT Results

SAT was performed on 1964 subjects. Of the tested patients, 673 (34.2%), including 275 (36.8%) males and 398 (32.7%) females, were positive for H. pylori antigens (Table 5). Although, no statistically significant association was found between SAT outcomes and sex (P value = 0.133), SAT was related to the age (P value = 0.00).


Table 5. Helicobacter pylori SAT Results
Criteria Helicobacter pylori SAT Results N
Negative Equivocal Positive
Gender Male 472 (63.2%) - 275 (36.8%) 747
Female 818 (67.2%) 1(0.1%) 398 (32.7%) 1217
Age group ≤5 84 - 6 90
6-15 170 - 13 183
16-30 268 - 109 377
31-45 364 - 270 635
46-60 274 - 191 465
61-75 113 - 78 191
>75 17 - 6 23
Total 1290 (65.7%) 1 (0.1%) 673 (34.3%) 1964

SAT:Stool antigen test.

UBT Results

At this stage, the UBT was applied to 141 patients. Of the total number of the investigated subjects for this test, 40 (28.36%) cases were positive with the mean age of 38.15 ± 12.28 years old.

Helicobacter pylori Infection Rate

Among the three methods used in this study, the most positive cases of H. pylori infection were identified by IgG, followed by SAT. The overall rate of H. pylori infection was 31.46%. The H. pylori infection rate was higher in the age group between 31-45 years old (37.92%), followed by 46-60 years old (35.61%), 61-75 years (34.47%), 16-30 years (29.36%), age >75 (27.52%), 6-15 years (9.33%), and age ≤5 (6.87%).


Discussion

Helicobacter pylori is a frequent human pathogen with a global prevalence of 44.3% (22). Although, improvements in health conditions and premier human growth indices have generally reduced the H. pylori infection outbreak rate in developed nations, its rate is still high in developing countries (23). Accordingly, to attain further achievements in the prevention and treatment results, the infection diagnosis in different regions is very important.

This study attempted to establish the prevalence of H. pylori infection amongst those patients who referred to the Fardis central laboratory located in Fardis county, Alborz province, Iran, from September 2020 to October 2021. A total of 5677 participants including 3486 (61.4%) females and 2191 (38.6%) males with ages ranging from 1 to 92 years old were examined using ELISA IgG, IgA, IgM, UBT, and SAT. According to the results, the total prevalence of H. pylori infections among those investigated patients was 31.46%, which is in agreement with what was reported in Nepal (26.6%), Uganda (24.3%), Taiwan (29.51%), and France (36.5%) (24-27). Further studies published in all over the world indicated the different rates of H. pylori infection such as China with 63.80%, Iran with 64%, and Nigeria with 81.7% prevalence (28-30). These variations in prevalence could be attributed to different factors including geographical area, age, race, socioeconomic status, hygiene levels, life style, diagnostic method, type of study population, and eradication therapy (31,32).

Helicobacter pylori infection results in stimulation of local and systemic antibody responses. Furthermore, in the systemic reaction, an impermanent rise in IgM antibodies is detectable in the early stage of infection. After that, IgG and IgA antibodies will emerge and still remain high until the time the infection is removed. Serological detection of H. pylori specific antibodies using serum-based ELISA is the most common non-invasive method for this pathogen diagnosis (33,34).

According to the results of this study, the seropositivity against H. pylori using ELISA kit for IgG, IgM, and IgA antibodies was 53.1%, 1.1%, and 0.2%, respectively. Some researchers reported 57.6% and 60.5% rates for IgG (35,36) that are in agreement with our results, while others reported 72.9%, 60%, and 21.2% rates which are inconsistent with our findings (29,37,38). The results of IgA were consistent with an earlier study which was 2.64% (39). However, other studies found 18% and 67.4%, which are inconsistent with our results (40,41). The IgM results were in accordance with those studies, reporting that 2.4%, 5.2%, and 5.81% of the subjects were positive for H. pylori (37,42,43). On the other hand, IgM seropositivity was 16.1% and 34.9% in some studies (44,41) that are inconsistent with our findings. The differences observed between various studies may be caused by the nature of the antigens used in the kits, infection stage, and sample size. The obtained results in this study demonstrated a significant association between serum levels of these antibodies and age increase. The IgG and IgA seropositive cases were significantly higher amongst the age group 31-75 years old, and the IgM seropositivity was significantly higher amongst the age groups 16-30, 6-15, and 31-45 years old, respectively. These findings are in agreement with several studies which found a significant effect of age increase on the levels of H. pylori seropositive cases (44,45), whilst others indicated contrasting results (38,46). In terms of gender, similar to an earlier study, no significant association was observed between IgG and IgA levels and sex, but positive cases of IgM were significantly higher in women compared to men (42). However, there is a conflict between our results and another study, which indicated higher IgG, IgM, and IgA seroprevalence cases in men compared with women (45).

SAT is a reliable test with high specificity and sensitivity that identify H. pylori antigens in stool (47). In this study, the total rate of stool antigen of H. pylori infection was 34.27%. This rate is comparable with the work of other researchers that reported 30.4% and 41% prevalence, respectively (36,48). However, some authors indicated 80.5% and 67.4%, which differs from results of the current study (49,50). Overconsumption of antibiotics is the most probable reason for the lower rate of infection amongst Iranian patients. The other causes of these differences might be attributed to the presence of patients with asymptomatic gastrointestinal bleeding in the investigated population and the condition of specimens like unformed or watery stool samples, preservation, and transportation. In this study, stool antigen detection did not indicate any significant association with gender, confirming an earlier report (51). However, it is in contrast with other investigations which indicated that females or males were more infected (50,52). Additionally, this study found a significant association with age that was similar to other published results by other studies (48,51), while contradictory results were reported elsewhere (52).

UBT is the most accurate and convenient non-invasive diagnostic assay for determining the H. pylori infection that is based on the H. pylori urease activity measurement (53). With respect to UBT results in this study, 28.36% with the mean age of 38.15 ± 12.28 years old were diagnosed with H. pylori infection. This rate is consistent with a prevalence of 32.3 % from a recent study (54) and is also inconsistent with other investigations by prevalence rates of 17% and 52.2%, respectively (55,56). The history of proton pump inhibitors and antibiotic consumption are expected to influence the UBT test results.

In recent years, a reduction in H. pylori prevalence was observed in some parts of the world (57-59). In this study, it was also observed that the prevalence of H. pylori infection has significantly reduced in comparison with a previous similar study performed at the same laboratory in 2015 (83.77% vs 31.46%) (60). It appears that the bacterial outbreak reduction may be caused by increasing the knowledge of people about this bacterium, hygienic condition improvement, as well as the development of appropriate treatment strategies by passing the time. Investigation of the studied methods in this research showed that serological tests (i.e., ELISA) are still the most commonly prescribed tests to detect the specific antibodies. Since antibodies, especially IgG, remain in the serum for a long time even after the bacteria have been suppressed, they do not differentiate between new and previous H. pylori infections and can yield false-positive results. Therefore, it is better to use serological tests for initial diagnosis and then confirm the results by another high-specificity test such as SAT.


Conclusions

The highest percentage of H. pylori was detected using by ELISA IgG (53.1%) and also the lowest ELISA IgA test (0.2%). There was a statistically significant association between H. pylori prevalence and age. No significant difference was found in H. pylori rate between the two genders, except in the case of IgM, which was higher in females compared to males. In addition, this study indicated a decline in the H. pylori infection prevalence compared to a previous study conducted at the same center. Despite the declining trend observed in this study, the outbreak of H. pylori amongst those patients who referred to Fardis laboratory is still high. Therefore, further preventive measures against H. pylori infection should be considered worthwhile. Moreover, we recommend conducting further studies with a larger sample size and sufficient time to evaluate the bacterium outbreak more precisely.


Acknowledgments

The authors are grateful to the research staff of the Department of Medical Laboratory Sciences, Faculty of Allied Medicine, Iran University of Medical Sciences, Tehran, Iran, for their contribution to improve the quality of this study.


Authors’ Contribution

Study Design: MJG, NR. Data Collection: ZY, MS, and PRA. Statistical Analysis: JZ. Data Interpretation: NR, PRA. Manuscript Preparation: NR, PRA. Literature Search: PRA.


Conflict of Interests

The authors declare no conflict of interests.


Ethical Approval

Informed consent was obtained from all participants before the study. The patients’ demographic characteristics were recorded in a questionnaire, and their information remained confidential. The Research and Ethics Committee of the Iran University of Medical Sciences approved all aspects of this study.


References

  1. Shahbazi S, Vahdat Shariatpanahi Z. Comparison between daily single-dose triple therapy and conventional triple therapy on patient compliance and Helicobacter pylori eradication: a randomized controlled trial. Indian J Gastroenterol 2018; 37(6):550-4. doi: 10.1007/s12664-018-0916-z [Crossref] [ Google Scholar]
  2. Ghasemian Safaei H, Faghri J, Moghim S, Nasr Esfahani B, Fazeli H, Makvandi M. Production of IFN-γ and IL-4 against intact catalase and constructed catalase epitopes of Helicobacter pylori from T-cells. Jundishapur J Microbiol 2015; 8(12):e24697. doi: 10.5812/jjm.24697 [Crossref] [ Google Scholar]
  3. Kayano T, Lee KD, Nishiura H. Estimating the force of infection with Helicobacter pylori in Japan. Can J Infect Dis Med Microbiol 2019; 2019:1451490. doi: 10.1155/2019/1451490 [Crossref] [ Google Scholar]
  4. Mirzaei N, Poursina F, Moghim S, Rashidi N, Ghasemian Safaei H. The study of H. pylori putative candidate factors for single- and multi-component vaccine development. Crit Rev Microbiol 2017; 43(5):631-50. doi: 10.1080/1040841x.2017.1291578 [Crossref] [ Google Scholar]
  5. Kamboj AK, Cotter TG, Oxentenko AS. Helicobacter pylori: the past, present, and future in management. Mayo Clin Proc 2017; 92(4):599-604. doi: 10.1016/j.mayocp.2016.11.017 [Crossref] [ Google Scholar]
  6. Talebi Bezmin Abadi A. Diagnosis of Helicobacter pylori using invasive and noninvasive approaches. J Pathog 2018; 2018:9064952. doi: 10.1155/2018/9064952 [Crossref] [ Google Scholar]
  7. Tsay FW, Hsu PI. Hpylori infection and extra-gastroduodenal diseases. J Biomed Sci 2018; 25(1):65. doi: 10.1186/s12929-018-0469-6 [Crossref] [ Google Scholar]
  8. Bravo D, Hoare A, Soto C, Valenzuela MA, Quest AF. Helicobacter pylori in human health and disease: mechanisms for local gastric and systemic effects. World J Gastroenterol 2018; 24(28):3071-89. doi: 10.3748/wjg.v24.i28.3071 [Crossref] [ Google Scholar]
  9. Xu MY, Cao B, Chen Y, Musial N, Wang S, Yin J. Association between Helicobacter pylori infection and tumor markers: an observational retrospective study. BMJ Open 2018; 8(8):e022374. doi: 10.1136/bmjopen-2018-022374 [Crossref] [ Google Scholar]
  10. Muhammad JS, Eladl MA, Khoder G. Helicobacter pylori-induced DNA methylation as an epigenetic modulator of gastric cancer: recent outcomes and future direction. Pathogens 2019; 8(1):23. doi: 10.3390/pathogens8010023 [Crossref] [ Google Scholar]
  11. Rashidi N, Moghim S, Fagheri J, Ghasemian Safaei H. Catalase epitopes vaccine design for Helicobacter pylori: a bioinformatics approach. Afr J of Biotechnol 2011; 10(44):8895-901. doi: 10.5897/ajb11.741 [Crossref] [ Google Scholar]
  12. Omosor KI, Omosor OH, Adejumo BI, Ibeh IN, Dimkpa U. Comparative evaluation of stool antigen immunoassay and blood antibody test methods for the screening of Helicobacter pylori infection in asymptomatic adult population in Delta State, Nigeria. J Mol Microbiol 2018; 2(1):1-7. [ Google Scholar]
  13. Wawro N, Amann U, Butt J, Meisinger C, Akmatov MK, Pessler F. Helicobacter pylori seropositivity: prevalence, associations, and the impact on incident metabolic diseases/risk factors in the population-based KORA study. Front Public Health 2019; 7:96. doi: 10.3389/fpubh.2019.00096 [Crossref] [ Google Scholar]
  14. Sabbagh P, Javanian M, Koppolu V, Vasigala VR, Ebrahimpour S. Helicobacter pylori infection in children: an overview of diagnostic methods. Eur J Clin Microbiol Infect Dis 2019; 38(6):1035-45. doi: 10.1007/s10096-019-03502-5 [Crossref] [ Google Scholar]
  15. Gravina AG, Zagari RM, De Musis C, Romano L, Loguercio C, Romano M. Helicobacter pylori and extragastric diseases: a review. World J Gastroenterol 2018; 24(29):3204-21. doi: 10.3748/wjg.v24.i29.3204 [Crossref] [ Google Scholar]
  16. Agbor NE, Esemu SN, Ndip LM, Tanih NF, Smith SI, Ndip RN. Helicobacter pylori in patients with gastritis in West Cameroon: prevalence and risk factors for infection. BMC Res Notes 2018; 11(1):559. doi: 10.1186/s13104-018-3662-5 [Crossref] [ Google Scholar]
  17. Pan X, Ke H, Niu X, Li S, Lv J, Pan L. Protection against Helicobacter pylori Infection in BALB/c mouse model by oral administration of multivalent epitope-based vaccine of cholera toxin B subunit-HUUC. Front Immunol 2018; 9:1003. doi: 10.3389/fimmu.2018.01003 [Crossref] [ Google Scholar]
  18. Tonkic A, Vukovic J, Vrebalov Cindro P, Pesutic Pisac V, Tonkic M. Diagnosis of Helicobacter pylori infection: a short review. Wien Klin Wochenschr 2018; 130(17-18):530-4. doi: 10.1007/s00508-018-1356-6 [Crossref] [ Google Scholar]
  19. Ansari S, Yamaoka Y. Current understanding and management of Helicobacter pylori infection: an updated appraisal. F1000Res 2018;7. 10.12688/f1000research.14149.1.
  20. Jalaly JB, Couturier MR, Burnham CD, Gronowski AM, Munigala S, Theel ES. Multicenter evaluation of Helicobacter pylori IgG antibody seroprevalence among patients seeking clinical care in the US. J Appl Lab Med 2018; 2(6):904-13. doi: 10.1373/jalm.2017.025569 [Crossref] [ Google Scholar]
  21. Sabbagh P, Mohammadnia-Afrouzi M, Javanian M, Babazadeh A, Koppolu V, Vasigala VR. Diagnostic methods for Helicobacter pylori infection: ideals, options, and limitations. Eur J Clin Microbiol Infect Dis 2019; 38(1):55-66. doi: 10.1007/s10096-018-3414-4 [Crossref] [ Google Scholar]
  22. Zamani M, Ebrahimtabar F, Zamani V, Miller WH, Alizadeh-Navaei R, Shokri-Shirvani J. Systematic review with meta-analysis: the worldwide prevalence of Helicobacter pylori infection. Aliment Pharmacol Ther 2018; 47(7):868-76. doi: 10.1111/apt.14561 [Crossref] [ Google Scholar]
  23. Basílio ILD, Catão MFC, de Sousa Carvalho, Freire-Neto FP, Ferreira LC, Jerônimo SMB. Risk factors of Helicobacter pylori infection in an urban community in Northeast Brazil and the relationship between the infection and gastric diseases. Rev Soc Bras Med Trop 2018; 51(2):183-9. doi: 10.1590/0037-8682-0412-2016 [Crossref] [ Google Scholar]
  24. Khadka P, Chapagain G, Maharjan G, Paudyal P. A comparison of techniques to address the frequency of Helicobacter pylori positive dyspeptic patient. BMC Res Notes 2018; 11(1):784. doi: 10.1186/s13104-018-3897-1 [Crossref] [ Google Scholar]
  25. Aitila P, Mutyaba M, Okeny S, Ndawula Kasule M, Kasule R, Ssedyabane F. Prevalence and risk factors of Helicobacter pylori infection among children aged 1 to 15 years at Holy Innocents Children’s Hospital, Mbarara, South Western Uganda. J Trop Med 2019; 2019:9303072. doi: 10.1155/2019/9303072 [Crossref] [ Google Scholar]
  26. Chen TH, Hsu CM, Cheng HT, Chu YY, Su MY, Hsu JT. Linked color imaging can help gastric Helicobacter pylori infection diagnosis during endoscopy. J Chin Med Assoc 2018; 81(12):1033-7. doi: 10.1016/j.jcma.2018.03.006 [Crossref] [ Google Scholar]
  27. Bénéjat L, Ducournau A, Lehours P, Mégraud F. Real-time PCR for Helicobacter pylori diagnosisThe best tools available. Helicobacter 2018; 23(5):e12512. doi: 10.1111/hel.12512 [Crossref] [ Google Scholar]
  28. Song Y, Dou F, Zhou Z, Yang N, Zhong J, Pan J. Microarray-based detection and clinical evaluation for Helicobacter pylori resistance to clarithromycin or levofloxacin and the genotype of CYP2C19 in 1083 patients. Biomed Res Int 2018; 2018:2684836. doi: 10.1155/2018/2684836 [Crossref] [ Google Scholar]
  29. Ghasemian Safaei H, Fazeli A, Tamizifar H, Rashidi N. Comparison of salivary anti Helicobacter pylori IgG with serum IgG and bacteriological tests in detecting Helicobacter pylori infections. J Res Med Sci 2005; 10(1):1-5. [ Google Scholar]
  30. Bello AK, Umar AB, Borodo MM. Prevalence and risk factors for Helicobacter pylori infection in gastroduodenal diseases in Kano, Nigeria. Afr J Med Health Sci 2018; 17(1):41-6. doi: 10.5897/ajmhs.9000010 [Crossref] [ Google Scholar]
  31. Melese A, Genet C, Zeleke B, Andualem T. Helicobacter pylori infections in Ethiopia; prevalence and associated factors: a systematic review and meta-analysis. BMC Gastroenterol 2019; 19(1):8. doi: 10.1186/s12876-018-0927-3 [Crossref] [ Google Scholar]
  32. Abbas M, Sharif FA, Osman SM, Osman AM, El Sanousi SM, Magzoub M. Prevalence and associated symptoms of Helicobacter pylori infection among schoolchildren in Kassala State, East of Sudan. Interdiscip Perspect Infect Dis 2018; 2018:4325752. doi: 10.1155/2018/4325752 [Crossref] [ Google Scholar]
  33. Pandya HB, Patel JS, Agravat HH, Singh NK. Non-invasive diagnosis of Helicobacter pylori: evaluation of two enzyme immunoassays, testing serum IgG and IgA response in the Anand district of central Gujarat, India. J Clin Diagn Res 2014; 8(6):DC12-5. doi: 10.7860/jcdr/2014/7578.4480 [Crossref] [ Google Scholar]
  34. Kamarehei F, Khabiri A, Saidijam M, Soleimani M, Alikhani MY. Designing a novel ELISA method based on CagA, NapA recombinant antigens to increase sensitivity and specificity of Helicobacter pylori whole cell antigen detection. Gastroenterol Hepatol Bed Bench 2018; 11(4):333-42. [ Google Scholar]
  35. Niknam R, Fattahi MR, Sepehrimanesh M, Safarpour A. Prevalence of Helicobacter pylori in southern part of Iran. Jundishapur J Microbiol 2018; 11(6):e62379. doi: 10.5812/jjm.62379 [Crossref] [ Google Scholar]
  36. Seid A, Demsiss W. Feco-prevalence and risk factors of Helicobacter pylori infection among symptomatic patients at Dessie Referral Hospital, Ethiopia. BMC Infect Dis 2018; 18(1):260. doi: 10.1186/s12879-018-3179-5 [Crossref] [ Google Scholar]
  37. Kalantar E, Gharavi MJ, Oshaghi M, Gharegozlou B, Mohammadi S, Heshmat R. Seroprevalence of Helicobacter pylori infection in Iranian adolescents: the CASPIAN-III study. Int J Pediatr 2017; 5(1):4251-6. doi: 10.22038/ijp.2016.7974 [Crossref] [ Google Scholar]
  38. Priyadarshini DR, Easow JM, Vinod R. Seroprevalence of Helicobacter pylori among healthy blood donors. Int J Curr Microbiol Appl Sci 2018; 7(2):817-22. doi: 10.20546/ijcmas.2018.702.103 [Crossref] [ Google Scholar]
  39. Abdollahi A, Shoar S, Jafari S, Emadi-Kochak H. Seroprevalence of Helicobacter pylori in human immunodeficiency virus-positive patients and it’s correlation with CD4+ lymphocyte count. Niger Med J 2014; 55(1):67-72. doi: 10.4103/0300-1652.128176 [Crossref] [ Google Scholar]
  40. Loesnihari R. Detection of Hpylori infection on dyspepsia patients with IgA H. pylori antibody. IOP Conf Ser Earth Environ Sci 2018; 125:012014. doi: 10.1088/1755-1315/125/1/012014 [Crossref] [ Google Scholar]
  41. Saghafi M, Abdolahi N, Orang R, Hatef MR, Molseghi MH. Helicobacter pylori infection in Sjögren’s syndrome: co-incidence or causality?. Curr Rheumatol Rev 2019; 15(3):238-41. doi: 10.2174/1573397114666181113102427 [Crossref] [ Google Scholar]
  42. Salehi M, Ghasemian A, Shokouhi Mostafavi SK, Najafi S, Rajabi Vardanjani H. Sero-prevalence of Helicobacter pylori infection in Neyshabur, Iran, during 2010-2015. Iran J Pathol 2017; 12(2):183-8. [ Google Scholar]
  43. Saadi HM, Saeed AY. Evaluation the efficacy of ELISA IgG, IgM and IgA tests for diagnosis of Helicobacter pylori. Kurd J Appl Res 2018; 3(2):172-6. doi: 10.24017/science.2018.2.29 [Crossref] [ Google Scholar]
  44. Dadashi A, Hosseinzadeh N. High seroprevalence of anti-Helicobacter pylori antibodies in patients with ventilator-associated pneumonia. J Res Med Sci 2018; 23:79. doi: 10.4103/jrms.JRMS_117_18 [Crossref] [ Google Scholar]
  45. Al-Balushi MS, Al-Busaidi JZ, Al-Daihani MS, Shafeeq MO, Hasson SS. Sero-prevalence of Helicobacter pylori infection among asymptomatic healthy Omani blood donors. Asian Pac J Trop Dis 2013; 3(2):146-9. doi: 10.1016/s2222-1808(13)60059-6 [Crossref] [ Google Scholar]
  46. Talib GA, Assi WT, Ibrahim AI. Prevalence of Helicobacter pylori infection in patients with peptic ulcer disease and non-ulcer dyspepsia and comparison among six diagnostic methods. Int J Acad Sci Res 2017; 5(4):11-20. [ Google Scholar]
  47. Miftahussurur M, Yamaoka Y. Diagnostic methods of Helicobacter pylori infection for epidemiological studies: critical importance of indirect test validation. Biomed Res Int 2016; 2016:4819423. doi: 10.1155/2016/4819423 [Crossref] [ Google Scholar]
  48. Khoder G, Muhammad JS, Mahmoud I, Soliman SSM, Burucoa C. Prevalence of Helicobacter pylori and its associated factors among healthy asymptomatic residents in the United Arab Emirates. Pathogens 2019; 8(2):44. doi: 10.3390/pathogens8020044 [Crossref] [ Google Scholar]
  49. Moon HW, Lee SY, Hur M, Yun YM. Characteristics of Helicobacter pylori-seropositive subjects according to the stool antigen test findings: a prospective study. Korean J Intern Med 2018; 33(5):893-901. doi: 10.3904/kjim.2016.353 [Crossref] [ Google Scholar]
  50. Aje AO, Otegbayo JA, Odaibo GN, Bojuwoye BJ. Comparative study of stool antigen test and serology for Helicobacter pylori among Nigerian dyspeptic patients--a pilot study. Niger J Clin Pract 2010; 13(2):120-4. [ Google Scholar]
  51. Talaiezadeh A, Borhani M, Moosavian M, Rafiei A, Neisi AK, Hajiani E. Prevalence of Helicobacter pylori infection evaluated by stool antigen test in Khuzestan province since September to October 2009, south-west of Iran: a population based study. Jundishapur J Microbiol 2013; 6(2):100-4. doi: 10.5812/jjm.4545 [Crossref] [ Google Scholar]
  52. Namakin K, Basiri Nejad F. Prevalence of Helicobacter pylori infection in asymptomatic children in Birjand, Eastern Iran. Int J Pediatr 2014; 2(2-4):55-63. [ Google Scholar]
  53. Graham DY, Miftahussurur M. Helicobacter pylori urease for diagnosis of Helicobacter pylori infection: a mini review. J Adv Res 2018; 13:51-7. doi: 10.1016/j.jare.2018.01.006 [Crossref] [ Google Scholar]
  54. Iannone A, Giorgio F, Russo F, Riezzo G, Girardi B, Pricci M. New fecal test for non-invasive Helicobacter pylori detection: a diagnostic accuracy study. World J Gastroenterol 2018; 24(27):3021-9. doi: 10.3748/wjg.v24.i27.3021 [Crossref] [ Google Scholar]
  55. Toyoshima O, Nishizawa T, Arita M, Kataoka Y, Sakitani K, Yoshida S. Helicobacter pylori infection in subjects negative for high titer serum antibody. World J Gastroenterol 2018; 24(13):1419-28. doi: 10.3748/wjg.v24.i13.1419 [Crossref] [ Google Scholar]
  56. Jemilohun AC, Ajani MA, Ngubor TD. Helicobacter pylori prevalence by urea breath test in a southwestern Nigerian population. J Gastroenterol Hepatol Res 2019; 8(1):2819-22. [ Google Scholar]
  57. Hanafi MI, Mohamed AM. Helicobacter pylori infection: seroprevalence and predictors among healthy individuals in Al Madinah, Saudi Arabia. J Egypt Public Health Assoc 2013; 88(1):40-5. doi: 10.1097/01.EPX.0000427043.99834.a4 [Crossref] [ Google Scholar]
  58. Eshraghian A. Epidemiology of Helicobacter pylori infection among the healthy population in Iran and countries of the Eastern Mediterranean region: a systematic review of prevalence and risk factors. World J Gastroenterol 2014; 20(46):17618-25. doi: 10.3748/wjg.v20.i46.17618 [Crossref] [ Google Scholar]
  59. Wang C, Nishiyama T, Kikuchi S, Inoue M, Sawada N, Tsugane S. Changing trends in the prevalence of Hpylori infection in Japan (1908-2003): a systematic review and meta-regression analysis of 170,752 individuals. Sci Rep 2017; 7(1):15491. doi: 10.1038/s41598-017-15490-7 [Crossref] [ Google Scholar]
  60. Gharavi MJ, Ebadi M, Fathi H, Yazdanyar Z, Setayesh Valipor N, Afrogh P. Trends in the prevalence of Helicobacter pylori infection in Fardis, Iran, 2011-2014. Int J Enteric Pathog 2016; 4(1):e32860. doi: 10.17795/ijep32680 [Crossref] [ Google Scholar]