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 as13C or14C, 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

The role of immunoglobulin E in airway remodeling in asthma

ABSTRACTImmunoglobulin E (IgE) plays an important role in the pathogenesis of asthma, a chronic disease of the airways characterized often by inflammation and remodeling. In a large proportion of asthmatic patients, anti-IgE therapy is effective in controlling their symptoms. The exact target sites of anti-IgE are not well characterized; however, it has been proposed that the therapeutic effects of anti-IgE come from its intervention of the inflammation and airway remodeling process. IgE acts on two types of receptors: a high affinity receptor and a low affinity receptor. The high affinity receptor or Fc epsilon RI (FcεRI), has been reported to express on inflammatory cells such as mast cells, basophils and eosinophils. An allergen, upon re-exposure, cross-links the membrane bound IgE-receptor complex and leads to the degranulation and release of mediators including histamine and prostaglandins, which in turn drive airway inflammation in asthma. In addition to inflammatory cells, FcεRI has also been reported to express on airway structural cells such as airway smooth muscle cells, where it enhances the production of extracellular matrix (ECM) proteins, proliferation of airway smooth muscle cells (ASMC) and release of cytokines. Airway epithelial cells are involved in the remodeling process by producing remodeling associated cytokines such as transforming growth factor–beta (TGF)-β and thymic stromal lymphopoietin (TSLP). Although FcεRI has also been reported to express on airway epithelial cells, the findings are elusive. To gain an insight on how anti-IgE therapy improves asthma symptoms, in this study we aimed to validate the expression of FcεRI on airway epithelial cells and demonstrate its role in airway remodeling. We measured the expression of FcεRI (1) in situ in bronchial biopsy tissues of asthmatic and control subjects using immunohistochemistry and (2) in vitro in primary human bronchial epithelial cells obtained from asthmatic subjects, at baseline and after treatment with human IgE, using qPCR and flow cytometry. FcεRI expression in situ was detected only in a very small number of cells in the epithelium of bronchial biopsies of asthmatic and control subjects. In vitro measurement revealed no expression of the receptor both at baseline and after treatment with IgE. To convincingly conclude the absence of FcεRI in bronchial epithelial cells, we incubated cells with crosslinking antibody and examined the downstream effects of IgE (i.e. the release of TSLP and TGF-β cytokines) using ELISA. No significant difference in TSLP and TGF-β protein releases was detected between stimulated and unstimulated cells. Hence, our data conclusively indicated that bronchial epithelial cells do not express functional high affinity receptor for IgE. Anti-IgE is therefore likely to exert its therapeutic effects via other structural cell types.RÉSUMÉL'immunoglobuline E (IgE) joue un rôle important dans la pathogenèse de l'asthme, une maladie chronique des voies respiratoires souvent caractérisée par l'inflammation et le remodelage. Pour un grand nombre de patients asthmatiques, la thérapie anti-IgE est efficace pour contrôler leurs symptômes. Les sites cibles de l'anti-IgE ne sont pas bien caractérisés; Cependant, il a été proposé que les effets thérapeutiques de l'anti-IgE viennent de son intervention dans processus de inflammation et remodelage des voies aériennes. L'IgE agit sur deux types de récepteurs: un récepteur à haute affinité et un récepteur à faible affinité. Il a été publié que le récepteur à haute affinité ou Fc epsilon RI (FcεRI) est exprimé sur des cellules inflammatoires telles que des mastocytes, des basophiles et des éosinophiles. Durant une ré-exposition, un allergène se lie de manière spécifique au récepteur IgE qui est lié à la membrane, et mène à la dégranulation et à la libération de médiateurs, comme l'histamine et les prostaglandines, qui entraînent une inflammation des voies respiratoires dans l'asthme. En plus des cellules inflammatoires, il a également été publié que le FcεRI est exprimé sur les cellules structurales des voies aériennes telles que les cellules des muscles lisses des voies aériennes, où il augmente la production de protéines de matrice extracellulaire (ECM), la prolifération des cellules musculaires lisses des voies aériennes (ASMC) et la libération de cytokines . Les cellules épithéliales des voies aériennes sont impliquées dans le processus de remodelage en produisant des cytokines associées au remodelage telles que le facteur de croissance transformant-bêta (TGF) -β et la lympopoïétine stromale thymique (TSLP). Bien que l'expression du FcεRI sur les cellules épithéliales des voies aériennes ait également été publiée, les résultats ne sont pas clairs. Dans cette étude, nous avons cherché à valider l'expression de FcεRI sur les cellules épithéliales des voies respiratoires et à démontrer son rôle dans le remodelage des voies aériennes. Nous avons mesuré l'expression de FcεRI (1) in situ dans les tissus de biopsie bronchique de sujets asthmatiques et sujets contrôles en utilisant l'immunohistochimie et (2) in vitro dans des cellules épithéliales bronchiques humaines primaires obtenues à partir de sujets asthmatiques, sans traitement et après traitement avec de l'IgE humaine, en utilisant la qPCR et la cytométrie en flux. L'expression de FcεRI in situ n'a été détectée que dans un très petit nombre de cellules dans l'épithélium de biopsies bronchiques d'asthmatiques et de sujets contrôles. Les résultats in vitro n'ont révélé aucune expression du récepteur sans et après traitement avec IgE. Pour conclure de façon convaincante l'absence de FcεRI dans les cellules épithéliales bronchiques, nous avons incubé des cellules avec un anticorps qui lui est spécifique et examiné les effets en aval de l'IgE (c'est-à-dire la libération de cytokines TSLP et TGF-β) par ELISA. Aucune différence significative dans les libérations des protéines TSLP et TGF-β n'a été détectée entre les cellules stimulées et non stimulées. Par conséquent, nos données indiquent de façon concluante que les cellules épithéliales bronchiques n'expriment pas de récepteur fonctionnel à haute affinité pour les IgE. L'anti-IgE est donc susceptible d'exercer ses effets thérapeutiques via d'autres cellulaires structurels

No evidence for IgE receptor FcεRI expression on bronchial epithelial cells of asthmatic patients

Immunoglobulin E (IgE) plays an important role in the pathogenesis of asthma and anti-IgE therapy was approved for treating patients with severe persistent allergic asthma. The exact target sites of anti-IgE therapy are not well characterized; however, it has been proposed that the therapeutic effects of anti-IgE come from its intervention in the airway remodeling process. To gain insights on how anti-IgE therapy improves asthma symptoms, we aimed to validate the expression of FcεRI on airway epithelial cells and demonstrate its role in airway remodeling. The expression of FcεRI was measured (1) in situ in bronchial biopsy tissues of asthmatic and control subjects using immunohistochemistry and (2) in vitro in primary bronchial epithelial cells obtained from asthmatic subjects, at baseline and after treatment with human IgE, using qPCR and flow cytometry. FcεRI expression in situ was detected only in a very small number of cells in the epithelium of bronchial biopsies of asthmatic and control subjects. In vitro measurement revealed no expression of the receptor both at baseline and after stimulation with IgE. The release of transforming growth factor—beta (TGF)-β and thymic stromal lymphopoietin (TSLP) were examined by ELISA in bronchial epithelial cells after crosslinking of IgE. No significant differences in TSLP and TGF-β protein levels were detected between stimulated and unstimulated cells. Hence, our data conclusively indicate that bronchial epithelial cells have negligible expression of functional high affinity receptor for IgE. Taken together, anti-IgE therapy is very likely to exert its therapeutic effects via other structural cell types