Use of a receiver operating characteristic in the evaluation of two commercial enzyme immunoassays for detection of Helicobacter pylori infection

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.

Antibody-based detection tests for the diagnosis of Helicobacter pylori infection in children: a meta-analysis

Background

Numerous serologic tests are available for the diagnosis of H. pylori infection in children. Common designs of antibody-based detection tests are ELISA and Western Blot (WB). For developing countries with limited laboratory resources and access, ELISA would be the preferred method because of its simplicity, lower cost and speed. Although in adults ELISA has proven to be highly accurate in diagnosing H. pylori infection; in children, it has shown variable accuracy.

Methods/Findings

We conducted a systematic review and meta-analysis to assess the accuracy of antibody-based detection tests for the diagnosis of H. pylori infection in children. Selection criteria included participation of at least 30 children and the use of a gold standard for H. pylori diagnosis. In a comprehensive search we identified 68 studies. Subgroup analyses were carried out by technique, immunoglobulin class, and source of test (commercial and in-house). The results demonstrated: 1) WB tests showed high overall performance, sensitivity 91.3% (95% CI, 88.9–93.3), specificity 89% (95% CI, 85.7–91.9), LR+ 8.2 (95% CI, 5.1–13.3), LR− 0.06 (95% CI, 0.02–0.16), DOR 158.8 (95% CI, 57.8–435.8); 2) ELISA-IgG assays showed low sensitivity 79.2% (95% CI, 77.3–81.0) and high specificity (92.4%, 95% CI, 91.6–93.3); 3) ELISA commercial tests varied widely in performance (test for heterogeneity p<0.0001); and 4) In-house ELISA with whole-cell antigen tests showed the highest overall performance: sensitivity 94% (95% CI, 90.2–96.7), specificity 96.4% (95% CI, 94.2–97.9), LR+ 19.9 (95% CI, 7.9–49.8), LR− 0.08 (95% CI, 0.04–0.15) DOR 292.8 (95% CI, 101.8–841.7).

Conclusions/Significance

WB test and in-house ELISA with whole-cell antigen tests are the most reliable tests for the diagnosis of H. pylori infection in children. Antigens obtained from local strains of the community could partially explain the good overall accuracy of the in-house ELISA. Because of its cost and technical demands, in-house ELISA might be more suitable for use in developing countries.

Helicobacter pylori detection and antimicrobial susceptibility testing

The discovery of Helicobacter pylori in 1982 was the starting point of a revolution concerning the concepts and management of gastroduodenal diseases. It is now well accepted that the most common stomach disease, peptic ulcer disease, is an infectious disease, and all consensus conferences agree that the causative agent, H. pylori, must be treated with antibiotics. Furthermore, the concept emerged that this bacterium could be the trigger of various malignant diseases of the stomach, and it is now a model for chronic bacterial infections causing cancer. Most of the many different techniques involved in diagnosis of H. pylori infection are performed in clinical microbiology laboratories. The aim of this article is to review the current status of these methods and their application, highlighting the important progress which has been made in the past decade. Both invasive and noninvasive techniques will be reviewed.

Comparison of different criteria for interpretation of immunoglobulin G immunoblotting results for diagnosis of Helicobacter pylori infection

Gastric infection with Helicobacter pylori is one of the most common chronic infections in humans, causing substantial morbidity and mortality. The diagnosis of H. pylori infection usually involves upper endoscopy with biopsy since the only noninvasive method of comparable accuracy, the [(13)C]urea breath test, requires technical equipment that is not available in most gastroenterological units. Serological methods for detection of H. pylori infection have reached sufficient accuracy to be used as screening tests before endoscopy or for seroepidemiological surveys. In the present study we evaluated different interpretation criteria for use with immunoglobulin G immunoblotting for the diagnosis of H. pylori infection. We applied five different sets of interpretation criteria, four of which had been published previously, to the Western blot results of 294 patients with different gastrointestinal symptoms. Since it is known that less than 2% of patients who are infected with H. pylori fail to seroconvert, an optimally sensitive Western blotting system should be able to detect approximately 98% of active infections. When the different criteria were applied to our patient population, it became apparent that the abilities of the systems to detect active H. pylori infection were quite varied. The results for the sensitivity and specificity, according to the different applied criteria, ranged from 62.8 to 95.9% and from 85.7 to 100.0%, respectively. Positive predictive values and negative predictive values, according to the published criteria, ranged from 97.2 to 100.0% and from 37.7 to 82.4%, respectively. Recommendations for the optimal use of the different interpretation criteria are discussed.

Seroprevalence of Helicobacter pylori infection in cystic fibrosis and its cross-reactivity with anti-pseudomonas antibodies

BACKGROUND

The prevalence of Helicobacter pylori infection and its role in gastroduodenal disease in cystic fibrosis (CF) are controversial. Additionally, serologic determination of infection in this population may be inaccurate because of cross-reactivity with other bacterial species. The seroprevalence of H. pylori in a cohort of patients with CF and its cross-reactivity with Pseudomonas antibodies were investigated.

METHODS

A research enzyme-linked immunosorbent assay (ELISA), and three commercial serologic assays (PyloriStat; BioWhittaker, Walkersville, MD, U.S.A.; Flexsure; SmithKline Diagnostics, Inc., San Jose, CA, U.S.A.; and HM-CAP; EPI, Stony Brook, NY, U.S.A.) at three independent laboratories determined the seroprevalence of anti-H. pylori IgG antibodies in 70 patients with CF. Cross-reactivity between solid-phase H. pylori antigens and Pseudomonas antibodies was ascertained by a competitive inhibition assay, preadsorbing sera of patients with CF with whole cell proteins from different Pseudomonas species, and serum reanalysis by each assay. Western blot analysis before and after adsorption was performed to identify potential cross-reactive antigens.

RESULTS

The research ELISA, Flexsure, Pyloristat, and HM-CAP initially showed H. pylori seropositivity of 47%, 28%, 24%, and 37%, respectively. Postadsorption seropositivity declined to 8%, 0%, 0%, and 15%, respectively. All patients with research ELISA true-positive results were confirmed endoscopically to have H. pylori infection. Western blot analysis showed a 31-kDa H. pylori protein with antigenic epitopes common to both bacterial species.

CONCLUSIONS

Cross-reactivity between solid-phase H. pylori antigens and anti-Pseudomonas antibodies occurs in patients with CF. A high index of suspicion should be assumed in evaluating results of serologic H. pylori tests in this population. Preadsorption of CF sera with Pseudomonas proteins should be used in serologic testing.

Helicobacter pylori infection and risk of cardia cancer and non-cardia gastric cancer. A nested case-control study

BACKGROUND

Helicobacter pylori infection is an established risk factor for gastric adenocarcinoma. Potential confounding by socioeconomic factors has not been adequately assessed, and the magnitude of the relative risk in relation to gastric subsites, morphologic subtypes, sex, age, and follow-up time need further study.

METHODS

We conducted a serologic case-control study nested within the Norwegian JANUS cohort. Between 1972 and 1986 serum was collected from 101,601 subjects who were followed up with regard to cancer development through 1992.

RESULTS

Among 208 gastric adenocarcinoma cases, we found a strong positive association between H. pylori infection and non-cardia gastric cancer (odds ratio (OR), 5.15; 95% confidence interval (CI), 2.83-9.37), and a statistically significant negative association with cardia cancer (OR, 0.40; 95% CI, 0.20-0.77). Adjustment for socioeconomic factors and smoking did not materially alter the effect estimates. The association between the infection and non-cardia cancer was stronger for tumors distal to the angulus and tended to be stronger in women than in men. The results were similar across Laurén morphologic subtypes.

CONCLUSIONS

These results strengthen the evidence of H. pylori infection as a risk factor in non-cardia gastric cancer. A negative association with H. pylori infection was found for cardia cancer.

Evaluation of enzyme-linked immunosorbent assay for the diagnosis of Helicobacter pylori infection in children from different age groups with and without duodenal ulcer

BACKGROUND

Although enzyme-linked immunosorbent assay (ELISA) is highly sensitive and specific for the diagnosis of Helicobacter pylori infection in adults, their performance in children is still controversial.

METHODS

A second-generation ELISA was used to evaluate the IgG response to H. pylori in the serum of 130 consecutive children who underwent upper gastrointestinal endoscopy. The presence of H. pylori was determined in antral biopsy specimens by culture, urease test, and histologic analysis.

RESULTS

Sixty-eight children (all of the 20 who had duodenal ulcer) were H. pylori positive by microbiologic test. Immunoglobulin G antibodies to H. pylori were detected in 79.4% of the infected children and in 8.1% of the noninfected ones. The sensitivity of the test was higher in patients with duodenal ulcer (100%) than in those without (70.8%). When used in children of different ages the test also presented differences in sensitivity: 44.4% in children 2 to 6 years old; 76.7% in children 7 to 11 years old, and 93.1% in children 12 to 16 years old (p = 0.006). The serum immunoglobulin G concentration was significantly higher (p = 0.0003) in children with duodenal ulcer than in those without and was higher in older children than in younger ones without duodenal ulcer (p = 0.05).

CONCLUSIONS

The accuracy of the test in children with duodenal ulcer and in children more than 12 years old was good; however, in children up to 12 years of age without duodenal ulcer, the sensitivity of the test was too low to be used for screening purposes or to rule out the presence of infection.

Serology and urea breath test in the diagnosis of H. pylori infection

Helicobacter pylori is a chronic infection that has the potential for causing and initiating serious gastric disease. Specific treatment can be successful in eradication of the infection but is currently complex which hampers essential patient compliance. Therefore, the accurate detection of H. pylori and, importantly, the post-treatment check for cure is vital in the effective management of this infection. This is especially true in cases of asymptomatic individuals. Serology is now a simple ELISA with a high degree of accuracy and has been shown to be useful as a screening tool prior to endoscopy in selected cases. The urea breath test, either using C13 or C14, is a sensitive test easily applied and is the test of choice for post-treatment check for cure. It is also the gold standard for the validation of serology in different populations.

Serodiagnosis of Helicobacter pylori infection by Cobas Core ELISA in adults from Minas Gerais, Brazil

We evaluated the accuracy of a 2nd generation ELISA to detect Helicobacter pylori infection in adults from a developing country in view of variations in sensitivity and specificity reported for different populations. We studied 97 non-consecutive patients who underwent endoscopy for evaluation of dispeptic symptoms. The presence of H. pylori was determined in antral biopsy specimens by culture, by the preformed urease test and in carbolfuchsin-stained smears. Patients were considered to be H. pylori positive if at least two of the three tests presented a positive result or if the culture was positive, and negative if the three tests were negative. Sixty-five adults (31 with peptic ulcer) were H. pylori positive and 32 adults were H. pylori negative. Antibodies were detected by Cobas Core anti-H. pylori EIA in 62 of 65 H. pylori-positive adults and in none of the negative adults. The sensitivity, specificity and positive and negative predictive values of the test were 95.4, 100, 100 and 91.4%, respectively. The Cobas Core anti-H. pylori EIA presented high sensitivity and specificity when employed for a population in Brazil, permitting the use of the test both to confirm the clinical diagnosis and to perform epidemiologic surveys.

Development of a PCR-restriction fragment length polymorphism assay using the nucleotide sequence of the Helicobacter hepaticus urease structural genes ureAB

Infection with Helicobacter hepaticus causes chronic active hepatitis in certain strains of mice and is associated with hepatocellular carcinoma in A/JCr mice. Like the gastric helicobacters, H. pylori and H. mustelae, H. hepaticus possesses a high level of urease activity. However, the H. hepaticus urease structural gene sequences have not been previously determined, and the role of the urease enzyme in colonization and in pathogenesis is not known. PCR was used to amplify a portion of the urease structural genes from H. hepaticus genomic DNA. Amplified DNA fragments were cloned, and the nucleotide sequence was determined. The deduced amino acid sequence of the partial H. hepaticus ureA gene product was found to exhibit 60% identity and 75% similarity to the predicted H. pylori UreA. The deduced amino acid sequence of a partial H. hepaticus ureB gene product exhibited 75% identity and 87% similarity to the predicted H. pylori UreB. Diversity among H. hepaticus isolates was evaluated by means of a restriction fragment length polymorphism (RFLP) assay. The 1.6-kb fragments within the ureAB open reading frames, amplified from 11 independent isolates, were digested with the restriction endonuclease HhaI. Three distinct RFLP patterns were observed. Identical RFLP profiles were noted in sequential isolates of one strain of H. hepaticus during an 18 month in vivo colonization study, suggesting that the urease genes of H. hepaticus are stable. The urease genes among H. hepaticus strains were also well conserved, showing 98.8 to 99% nucleotide sequence identity among three isolates analyzed. These findings indicate that H. hepaticus has urease structural genes which are homologous to those of the gastric Helicobacter species and that these gene sequences can be used in a PCR and RFLP assay for diagnosis of this important murine pathogen.

Development of FlexSure® HP—an immunochromatographic method to detect antibodies against Helicobacter pylori

We describe a solid-phase immunochromatographic serologic test, FlexSure® HP, to detect IgG antibodies against Helicobacter pylori. H. pylori colonize the stomach and proximal duodenum, cause ulcer disease and mucosa-associated lymphoid tissue lymphoma, and have a role in the development of other disorders, including gastric adenocarcinoma. FlexSure HP consists of a test strip, conjugate pad, and absorbent pad, in a novel reverse-flow chromatography format. In these studies, FlexSure HP was demonstrated to be specific for IgG antibodies against H. pylori. The reactive cutoff of the test was consistent with [13C]urea breath test and commercially available ELISAs. FlexSure HP had 94% sensitivity, 88% specificity, and 91% accuracy relative to [13C]urea breath test; and 95% sensitivity, 94% specificity, and 95% overall agreement relative to high-molecular-mass cell-associated protein enzyme immunoassay (HM-CAP EIA). FlexSure HP is a simple-to-perform, visually read test requiring no specialized training, equipment, or instrumentation, and yields rapid, accurate, qualitative results.

A new histological procedure for re-evaluation of the serological test for Helicobacter pylori

To re-evaluate the accuracy of the serological test for Helicobacter pylori, fixation of biopsy specimens with Carnoy's solution (preserving the mucous layer in tissue preparations) followed by immunohistochemical staining (a new histological procedure) was used as the reference histological method instead of 10% formalin fixation followed by hematoxylin-eosin staining (the conventional histological procedure). Biopsy specimens (antrum and body) from 114 patients with gastritis (including non-ulcer dyspepsia) or gastric and/or duodenal ulcers were obtained by endoscopy and used for both bacteriological culture and histological examination. Serum samples were taken from all patients at the time of endoscopy. The serum levels of specific IgG and IgA antibodies for Helicobacter pylori were measured by commercial enzyme immunoassay kits. The reliability of the IgG and IgA measurements was evaluated by analyzing receiver operating characteristic curves obtained using the two histological procedures. With the conventional histological procedure as the reference, the sensitivity and specificity levels of the serological test were 87.2% and 82.1%, respectively. With the new histological procedure as reference, sensitivity and specificity were 94% and 96.7%, respectively. The insufficient accuracy reported for the serological test could be due to false-positive or false-negative results obtained when the conventional histological procedure is used as the reference. The new histological procedure used here revealed that the serological test for Helicobacter pylori is more reliable than previously thought.

Evaluation of eight enzyme immunoassays for detection of immunoglobulin G against Helicobacter pylori

Eight commercial enzyme-linked immunosorbent assays (ELISAs) were used to test sera taken from 102 patients in whom Helicobacter pylori infection status had been determined by means of biopsy culture, PCR, histology, and urease production and by 13C urea breath test. By those means, 61 patients had been found to be infected. Assays were compared by receiver operating characteristic analysis. Sensitivities ranged from 86 to 98%; specificities ranged from 83 to 98%. In a group consisting of the assays by Bio-Whittaker, Meddens Biotech, Orion (Pyloriset EIA G, new version), and Enteric Products, Inc. (HM Cap), differences in performance were not statistically significant. Sensitivities in this group ranged from 93 to 98%; specificities ranged from 95 to 98%. Assays from this group may be useful in addition to biopsy-based methods in diagnosing H. pylori infection.

Accuracy of serology for the diagnosis of Helicobacter pylori infection--a comparison of eight kits

AIMS

To determine the accuracy of eight commercially available kits for the serological diagnosis of Helicobacter pylori infection, and hence whether a serology service could be introduced to reduce endoscopy workload.

METHODS

Eighty four patients newly presenting to their general practitioners with dyspepsia were recruited. Gold standard diagnosis of H pylori infection was obtained both by a histological examination of gastroduodenal biopsy specimens and by the 14C-urea breath test (UBT). The performance of six quantitative and two qualitative enzyme linked immunosorbent assays for H pylori IgG, used according to the manufacturers' instructions, with serum samples obtained during the endoscopy visit, were compared.

RESULTS

The study population had a median age of 45 years, and the prevalence of H pylori infection was 35%. With one exception, where the patient had received a course of anti-H pylori treatment between endoscopy and UBT, there was 100% concordance in the results of the two gold standard techniques. Discordant serology results were more common in patients aged > 50 years (42% of the total) than in younger patients (21%), and this was most noticeable in uninfected patients. The sensitivity of the kits was good (90-100%), but specificity was more variable (76-96%), and the rate of equivocal results was unacceptably high in some cases (0-12%). The overall accuracy of the kits ranged from 83 to 98%. Two kits in particular performed well (Pylori-Elisa II, Bio-Whitaker and Premier, Launch; qualitative) with 98% and 100% accuracy, respectively.

CONCLUSIONS

In a symptomatic population with a prevalence of H pylori infection of 35%, particularly in patients aged < 50 years, some but not all serology kits may be used as a highly accurate and inexpensive alternative to the gold standard techniques.

Cat owners' risk of acquiring a Helicobacter pylori infection

In order to obtain information as to whether or not domestic cats are a significant reservoir for human Helicobacter pylori infection, H. pylori antibodies were determined in 59 members of cat protection clubs and in an age- and sex-matched control group. Using four different assay systems, the prevalence rates of H. pylori antibodies in the cat owner group compared to the control group were 29% and 34%, respectively (Pyloriset Dry), 27%/42% (Pyloriset EIA-G), 14%/29% (Pyloriset EIA-A), and 37%/42% (Cobas Core EIA). The differences between the two groups in the prevalence of H. pylori antibodies were not statistically significant. It is concluded that cat owners, even if they have a very intensive contact with their pets, do not have a higher risk of H. pylori infection than the general population.