Validation of a rapid stool antigen test for diagnosis of Helicobacter pylori infection

Accuracy of Stool Antigen Test in the Diagnosis of Helicobacter pylori Infection in the Dominican Republic

Introduction: Helicobacter pylori is a well-studied infectious agent due to its pathogenic potential for peptic ulcers and gastric cancer. It has a high prevalence worldwide and has several diagnostic methods, both invasive and non-invasive. It is important to address the diagnostic efficacy of these tests, as the data vary by location and the specific population in which they are used. Therefore, an effective testing method should be obtained, evaluating the possibility of substantially reducing invasive procedures and, therefore, associated costs.

OBJECTIVE

This study proposes to define the diagnostic accuracy of the stool antigen test for H. pylori infection in the Dominican Republic.

METHODS

An observational, retrospective, and cross-sectional study was conducted. The results of the stool antigen test for H. pylori infection were compared with the results of the gastric biopsy, as a gold standard test. Patients over 18 years of age with an indication for endoscopy due to suspicion of H. pylori infection, who attended the gastroenterology clinic in 2021, were included in the study.

RESULTS

It was shown that the stool antigen test for H. pylori infection has a 61.54% sensitivity and 59.65% specificity. According to the study population, the positive predictive value (PPV) was 67.60% and the negative predictive value (NPV) was 53.13%.

CONCLUSION

Low numbers of both sensitivity and specificity were determined, which is why it is pertinent to study alternative non-invasive methods. However, it is important to assess the antibiotic exposure of the study population, since the diagnostic accuracy of the stool test can be influenced by this factor.

Evaluation of the diagnostic performance and the utility of Helicobacter pylori stool antigen lateral immunochromatography assay

Background

Helicobacter pylori causes the most common human gastric infection. H. pylori Stool Antigen Lateral Flow Immunochromatography assay (HpSA-LFIA) is considered one of the most cost-effective and rapid non-invasive assays (active tests). Evaluating HpSA-LFIA is of crucial for ensuring accuracy and utility assurance. This study aimed to evaluate the polyclonal antibody-based HpSA-LFIA in comparison to a monoclonal antibody-based ELISA kit.

Methodology

Stool samples were collected from 200 gastric patients for HpSA-LFIA and semiquantitative HpSA-ELISA tests. A statistical analysis of the diagnostic performance was performed using MedCalc software. Chi-square tests were performed to determine the effects of gender and age.

Results and conclusion

The results showed that HpSA-LFIA achieved remarkable sensitivity (93.75%) and NPV (98.00%). However, it had poor specificity, PPV, and accuracy of 59.76%, 31.25%, and 65.31%, respectively. LR+ and LR-were 2.33% & 0.1%, respectively. Gender didn't affect the diagnostic performance of HpSA-LFIA. Age groups had irrelevant sensitivity; however, specificity was significantly higher in patients aged >45 years. We can conclude that HpSA-LFIA was not accurate enough to be the sole test for diagnosis and suggest developing other confirmatory tests in case of positive conditions.

Evaluation of antibody immunochromatography testing for diagnosis of current Helicobacter pylori infection

Background

Helicobacter pylori infection represents a major gastrointestinal complaint associated with gastritis, gastric ulcer and stomach tumors. It is present in 90 % of developing countries population. H. pylori diagnosis in these countries, where resources are limited, is accomplished with simple non-invasive tests such as stool antigen and serum antibody tests. The aim of this study was to evaluate the serum antibody test in the diagnosis of current H. pylori infection.

Subject and methods

A total of 117 patients were included in this prospective diagnosis accuracy testing study, who clinically presented with dyspepsia, heartburn, abdominal pain, diarrhea, or halitosis. A stool sample was collected from each patient and tested for H. pylori antigen using immunochromatographic method.Blood sample was also collected, half of which was EDTA-sampled and analyzed for complete blood count, while the remaining half was left to clot, the separated serum was tested for antibodies against H. pylori with immunochromatographic cassette.

Results

About 35 % of sixty six patients who were positive for stool antigen test gave a negative for serum antibodies test. Meanwhile, the non-consistent results within 51 negative stool antigen test patients was exhibited by 47 % of them. The discrepancies were not affected by age or disease duration. The calculated sensitivity, specificity, positive predictive value and negative predictive values were 50 %, 65 %, 65 % and 50 % respectively.

Conclusion

The serum antibody test is not reliable in the diagnosis of current H. pylori infection. In developing countries, with limited facilities and primary care units, stool antigen test diagnosis is useful for diagnosis.

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Stool antigen detection versus 13C-urea breath test for non-invasive diagnosis of pediatric Helicobacter pylori infection in a limited resource setting

INTRODUCTION

The prevalence of childhood infection with Helicobacter pylori is high, especially in developing countries. Non-invasive methods for detection of infection in children should be inexpensive, easy to perform, well tolerated and have a high diagnostic accuracy. We aimed to compare the reliability, specificity and sensitivity of the H. pylori stool antigen (HpSA) test with the ¹³C-urea breath test (¹³C-UBT) for the diagnosis of H. pylori infection in a limited resource setting.

MATERIAL AND METHODS

The stool samples of 60 symptomatic and dyspeptic children with a mean age of 7.2 ±3.7 years (2-15 years) were evaluated using the rapid One step HpSA test by lateral flow immunoassay. The ¹³C-UBT was used as the gold standard method for the diagnosis of H. pylori infection.

RESULTS

The HpSA test detected H. pylori antigen in 34 out of 38 positive patients with 4 false-negatives (sensitivity 89.5%, 95% confidence interval (CI): 75.2-97.1%), while 21 patients had true-negative results and one false-positive (specificity 95.5%, 95% CI: 77.2-99.9%), with a strong measure of agreement between the HpSA test and the ¹³C-UBT (κ = 0.83, 95% CI: 68-97%, p < 0.001). It had a positive predictive value of 97.1% (95% CI: 85.1-99.9%), a negative predictive value of 84% (95% CI: 63.9-95.5%) and an accuracy of 91.7%.

CONCLUSIONS

The rapid lateral flow HpSA test is a reliable method for the primary diagnosis of H. pylori infections in children, though not as accurate as the ¹³C-UBT. It is more affordable, simpler to perform and more tolerable, representing a viable alternative, especially in developing countries.

Investigation of Helicobacter pylori antigen in stool samples of patients with upper gastrointestinal complaints

Helicobacter pylori infection is usually acquired in early childhood and it can persist throughout life without antibiotic treatment. This study aimed to compare the accuracy of the noninvasive H. pylori Stool Antigen Test-applied on the stool samples with the invasive gold standart Rapid Urease Test-applied on the gastric biopy samples of patients with upper gastrointestinal complaints. After endoscopy, biopsy and stool specimens were taken in 122 patients. The infection was detected with rapid urease test which is accepted as gold standart test. Rapid, one-step H. pylori card test was applied to all patients stool specimens. In this study 106 of the 122 patients (86.8%) were positive for H. pylori infection, while 16 of the 122 patients (13.2%) were negative. H. pylori card test was negative in 13 of the 16 patients and was positive in 98 of the 106. The sensitivity, specifity, positive and negative predictive values were 92.45%, 81.25%, 97.02%, and 61.90%, respectively. H. pylori card test is rapid, easy, noninvasive and inexpensive methods for detection H. pylori infection. This test showed high sensitivity and specificity. Additionally, it may be a good alternative to invasive tests for the detection of H. pylori infections especially in children.

Novel detection of Helicobacter pylori in fish: A possible public health concern

Helicobacter pylori is one of the most common human pathogens worldwide with serious clinical outcomes. Although, H. pylori is a major water-borne pathogen, its occurrence in fish is still unknown. This leads us to conduct the current study in order to clarify this point and to investigate the potential role of fish in the epidemiology of H. pylori. For this purpose, fecal samples were obtained from 315 fish from different species and were caught from various aquatic environments at different localities in Egypt. The obtained fecal samples were examined for the occurrence of H. pylori using monoclonal antibody based lateral flow immunoassay for antigen detection and after then the positive samples were confirmed by PCR. In addition, fecal samples from 18 fish handlers were also examined for the presence of H. pylori by lateral flow technique. The overall prevalence rates of H. pylori in the examined fish were 6.7% and 1.9% for LF and PCR, respectively, whereas 61.1% of fish handlers were positive. Only tilapia fish showed positive results by both techniques in rates 10.9% and 3.1%, respectively. Interestingly, H. pylori was detected in cultured and wild tilapia in various aquatic environments at different localities, whereas all other fish species were negative even those that were collected from the same water source where positive tilapia were caught. These results concluded that tilapia fish may be considered as a potential zoonotic reservoir for H. pylori and thus, H. pylori may become a new fish-borne pathogen. Further studies are needed to investigate the occurrence of H. pylori in other fish species.

Standard Triple Therapy versus Sequential Therapy in Helicobacter pylori Eradication: A Double-Blind, Randomized, and Controlled Trial

Aim. To compare 10-day standard triple therapy versus sequential therapy as first-line treatment in patients infected with H. pylori. Methods. One hundred H. pylori positive patients (diagnosed by rapid urease test and histology), with average age of 47.2, M/F = 28/72, were randomized to receive either standard triple treatment (TT) as follows: lansoprazole 30 mg, clarithromycin 500 mg, and amoxicillin 1 g, b.i.d. for ten days, or sequential treatment (ST) as follows: lansoprazole 30 mg, amoxicillin and placebo 1.0 g b.i.d for the first five days, followed by lansoprazole 30 mg, clarithromycin 500 mg, and tinidazole 500 mg b.i.d, for the remaining five days. Eradication rates were determined 60 days after treatment by urease, histology, or ¹³C-urea breath test. Results. In intention to treat (ITT) analysis, the rate of H. pylori eradication in the TT and ST groups was the same for both regimens as follows: 86% (43/50), 95% CI 93,3 to 73.4%. In Per protocol (PP) analysis, the rate of H. pylori eradication in the TT and ST groups was 87.8% (43/49), 95% CI 94,5 to 75.3% and 89.6% (43/48), 95% CI 95,8 to 77.3%, respectively. Conclusions. In Brazil, standard triple therapy is as equally effective as sequential therapy in eradicating Helicobacter pylori patients. This study was registered under Clinical Trials with number ISRCTN62400496.

Efficacy of levofloxacin, amoxicillin and a proton pump inhibitor in the eradication of Helicobacter pylori in Brazilian patients with peptic ulcers

OBJECTIVES

The eradication of Helicobacter (H.) pylori allows peptic ulcers in patients infected with the bacteria to be cured. Treatment with the classic triple regimen (proton pump inhibitor, amoxicillin and clarithromycin) has shown decreased efficacy due to increased bacterial resistance to clarithromycin. In our country, the eradication rate by intention to treat with this regimen is 83%. In Brazil, a commercially available regimen for bacterial eradication that uses levofloxacin and amoxicillin with lansoprazole is available; however, its efficacy is not known. Considering that such a treatment may be an alternative to the classic regimen, we aimed to verify its efficacy in H. pylori eradication.

METHODS

Patients with peptic ulcer disease infected with H. pylori who had not received prior treatment were treated with the following regimen: 30 mg lansoprazole bid, 1,000 mg amoxicillin bid and 500 mg levofloxacin, once a day for 7 days.

RESULTS

A total of 66 patients were evaluated. The patients' mean age was 52 years, and women comprised 55% of the sample. Duodenal ulcers were present in 50% of cases, and gastric ulcers were present in 30%. The eradication rate was 74% per protocol and 73% by intention to treat. Adverse effects were reported by 49 patients (74%) and were mild to moderate, with a prevalence of diarrhea complaints.

CONCLUSIONS

Triple therapy comprising lansoprazole, amoxicillin and levofloxacin for 7 days for the eradication of H. pylori in Brazilian peptic ulcer patients showed a lower efficacy than that of the classic triple regimen.

Evaluation of the Atlas Helicobacter pylori stool antigen test for diagnosis of infection in adult patients

BACKGROUND

Helicobacter pylori (H. pylori) is one of the most important causes of dyspepsia and gastric cancer and diagnosis can be made by invasive or non-invasive methods. The Atlas Helicobacter pylori antigen test is a new rapid non-invasive method which is simple to conduct. The aim of this study was to determine its sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV) and accuracy.

MATERIALS AND METHODS

This prospective study was conducted between July 2012 and December 2013. Stool samples of 59 dyspeptic patients who underwent upper endoscopy were evaluated for H. pylori stool antigen.

RESULTS

From the 59 patients who participated in this study, there were 36 (61%) males and 23 (39%) females. H. pylori was diagnosed in 24 (40.7%) gastric biopsies, 22 (91.7 %) of these being positive for the Atlas H. pylori antigen test. The sensitivity, specificity, PPV, NPV and accuracy were 91.7%, 100%, 100%, 94.6% and 96.6% respectively.

CONCLUSIONS

The Atlas H. pylori antigen test is a new non-invasive method which is simple to perform and avails reliable results in a few minutes. Thus it can be the best option for the diagnosis of H. pylori infection due to its high sensitivity and specificity.

Low dose capsule based 13c-urea breath test compared with the conventional 13c-urea breath test and invasive tests

CONTEXT

One of the limitations of 13C-urea breath test for Helicobacter pylori infection diagnosis in Brazil is the substrate acquisition in capsule presentation.

OBJECTIVES

The purpose of this study was to evaluate a capsule-based 13C-urea, manipulated by the Pharmacy Division, for the clinical practice.

METHODS

Fifty patients underwent the conventional and the capsule breath test. Samples were collected at the baseline and after 10, 20 and 30 minutes of 13C-urea ingestion. Urease and histology were used as gold standard in 83 patients.

RESULTS

In a total of 50 patients, 17 were positive with the conventional 13C-urea (75 mg) breath test at 10, 20 and 30 minutes. When these patients repeated breath test with capsule (50 mg), 17 were positive at 20 minutes and 15 at 10 and 30 minutes. The relative sensitivity of 13C-urea with capsule was 100% at 20 minutes and 88.24% at 10 and at 30 minutes. The relative specificity was 100% at all time intervals. Among 83 patients that underwent capsule breath test and endoscopy the capsule breath test presented 100% of sensitivity and specificity.

CONCLUSIONS

Capsule based breath test with 50 mg 13C-urea at twenty minutes was found highly sensitive and specific for the clinical setting.

Comparison of the diagnostic accuracy of five different stool antigen tests for the diagnosis of Helicobacter pylori infection

BACKGROUND

Several noninvasive diagnostic tests based on the detection of Helicobacter pylori stool antigen (HpSA) have been developed. The aim of the study was to compare the diagnostic accuracy of 5 HpSA tests-2 monoclonal enzyme immunoassay tests (EIAs: the Premier Platinum HpSA Plus test and Helicobacter pylori Antigen (Hp Ag) test) and 3 rapid immunochromatographic assay (ICA) tests (the ImmunoCard STAT! HpSA test, one step HpSA test, and H. pylori fecal antigen test)--for diagnosing H. pylori infection in adult patients with dyspeptic symptoms before eradication therapy.

MATERIALS AND METHODS

A total of 198 patients with dyspeptic symptoms were included in the study. A gastric biopsy was collected for histopathology and rapid urease testing. Stool specimens for HpSA testing were also collected. Patients were considered H. pylori positive if two invasive tests (histological and rapid urease tests) were positive.

RESULTS

The sensitivity and specificity were 92.2% and 94.4%, respectively, for the Premier Platinum HpSA Plus test; 48.9% and 88.9%, respectively, for the HP Ag test; 86.7% and 88.9, respectively, for the One Step HpSA test; 68.9% and 92.6%, respectively, for the ImmunoCard STAT! HpSA test; and 78.9% and 87%, respectively, for the H. Pylori fecal antigen test.

CONCLUSIONS

The Premier Platinum HpSA Plus EIA test was determined to be the most accurate stool test for diagnosing H. pylori infections in adult dyspeptic patients. The currently available ICA-based tests are fast and easy to use but provide less reliable results.

3rd Brazilian Consensus on Helicobacter pylori

Signicant progress has been obtained since the Second Brazilian Consensus Conference on Helicobacter pylori Infection held in 2004, in São Paulo, SP, Brazil, and justify a third meeting to establish updated guidelines on the current management of H. pylori infection. The Third Brazilian Consensus Conference on H pylori Infection was organized by the Brazilian Nucleus for the Study of Helicobacter, a Department of the Brazilian Federation of Gastroenterology and took place on April 12-15, 2011, in Bento Gonçalves, RS, Brazil. Thirty-one delegates coming from the five Brazilian regions and one international guest, including gastroenterologists, pathologists, epidemiologists, and pediatricians undertook the meeting. The participants were allocated in one of the five main topics of the meeting: H pylori, functional dyspepsia and diagnosis; H pylori and gastric cancer; H pylori and other associated disorders; H pylori treatment and retreatment; and, epidemiology of H pylori infection in Brazil. The results of each subgroup were submitted to a final consensus voting to all participants. Relevant data were presented, and the quality of evidence, strength of recommendation, and level of consensus were graded. Seventy per cent and more votes were considered as acceptance for the final statement. This article presents the main recommendations and conclusions to guide Brazilian doctors involved in the management of H pylori infection.

Upper gastrointestinal bleedings in patients with hereditary coagulation disorders in Northwest of Iran: prevalence of Helicobacter pylori infection

OBJECTIVE

Upper gastrointestinal (UGI) bleeding is one of the most life-threatening complications, in up to 25% of persons with hemophilia (PWH). Recurrent bleeding is common and can be caused by the Helicobacter pylori infection. Our aim was to evaluate the role of H. pylori infection in UGI bleeding in PWH.

MATERIAL AND METHODS

Ninety patients with hereditary bleeding disorders, 30 patients with (group A), and 60 patients without (group B) a history of UGI bleeding episodes were included. The prevalence of H. pylori infection was investigated by stool antigen test, and serum serologic tests including immunoglobulin G and anti-CagA.

RESULTS

Among 90 patients (81 men, nine women, mean age 31.30 ± 10.72 years), 66 patients with hemophilia A, 10 patients with hemophilia B, six patients with Von Willebrand disease, five patients with platelet function disorders, and three patients with other factor deficiencies were evaluated. About 46.7% of patients in group A, and 23.3% of patients in group B were anti-CagA-positive (P=0.02), whereas 76.7% of patients in group A and 51.7% of patients in group B had H. pylori immunoglobulin G antibodies (P=0.02). H. pylori antigen in stool was positive in 76.7% in group A and 55% in group B (P=0.03). No statistically significant difference was found between type and severity of diseases and risk of UGI.

CONCLUSION

H. pylori infection should be considered as an important cause of UGI bleeding in PWH. We would recommend stool antigen test as a new and noninvasive screening test for diagnosis of H. pylori infection in all patients with hereditary hemorrhagic disorders.

Diagnosis of Helicobacter pylori Infection

When an endoscopy is performed, it now becomes easier to observe indirect evidence of the presence of a Helicobacter pylori infection, given the progress of new methods including magnifying narrow band imaging or confocal laser endomicroscopy. Out of the biopsy-based tests, the novel original method proposed concerned culture in a broth medium with or without antibiotics and ELISA detection of H. pylori. New stool antigen tests are still appearing with no major improvement in comparison with the monoclonal-based tests already on the market. The combination of pepsinogen detection to H. pylori serology is now more and more evaluated to detect preneoplastic lesions.

Evaluation of a new antigen for diagnosis of Helicobacter pylori infection in stool of adult and children

BACKGROUND

Nowadays, there is an increasing interest in noninvasive methods to diagnose Helicobacter pylori infection. Indeed, they can profitably replace endoscopy in predicting the diagnosis. The stool antigen test for H. pylori is a noninvasive immunoassay to diagnose active infection with this bacterium in human fecal samples. The aim of this study was detection of alkyl hydroperoxide reductase protein (AhpC) antigen by immunoblotting in stool samples for diagnosis of H. pylori.

MATERIALS AND METHODS

Chromosomal DNA from H. pylori was isolated. AhpC gene was amplified by PCR, These amplicons were cloned into pTZ57R/T cloning vector then subcloned into pQE30 expression vector and overexpressed using isopropyl-beta-D-thiogalactopyranoside in E. coli M15. AhpC protein was purified by affinity chromatography. Rabbits were immunized with the purified AhpC protein for the production of antibodies. To determine the accuracy of the test for diagnosing H. pylori infection from stool, we evaluated 84 patients (6-81 years old) using Western blot analysis by rabbit anti-AhpC antibody. Positive rapid urease test on biopsy samples was considered as the gold standard.

RESULTS

AhpC gene was overexpressed, and AhpC protein was purified. Rabbit anti-AhpC antibody produced after immunization with the purified AhpC protein. By immunoblotting, we detected AhpC protein in the positive stool samples. The test showed a 83.3% sensitivity (95% CI: 69.8-92.5%) and a 91.7% specificity (95% CI: 77.5-98.2). Among the children, the sensitivity was 88.2% (95% CI: 63.6-98.5) and the specificity was 100% (95% CI: 69.2-100); in adults, the sensitivity and specificity were 80.6% (95% CI: 62.5-92.5) and 88.5% (95% CI: 69.8-97.6), respectively.

CONCLUSIONS

Using of AhpC antigen for diagnosis of H. pylori infection is a useful noninvasive method, accurate in adolescents and children, and can be used for the development of a stool antigen detection kit for H. pylori.