Helicobacter Pylori Infection Gut: First Published As 10.1136/Gut.45.2008.I23 on 1 July 1999
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Gut 1999;45(Suppl I):I23–I27 I23 New immunological assays for the diagnosis of Helicobacter pylori infection Gut: first published as 10.1136/gut.45.2008.i23 on 1 July 1999. Downloaded from D Vaira, J Holton, M Menegatti, C Ricci, F Landi, A Ali’, L Gatta, C Acciardi, S Farinelli, M Crosatti, S Berardi, M Miglioli Summary the detection of amplified products of the There are several types of immunological tests polymerase chain reaction (PCR)–DNA im- available for the diagnosis and management of munoassays. Helicobacter pylori infection. Most commer- cially available serological kits use the enzyme Current non-invasive immunological linked immunosorbent assay (ELISA) test for- tests mat. Originally the kits used crude antigen SEROLOGY preparations although many of the newer kits Several diVerent techniques exist for antibody use a more purified antigen preparation, with detection. Solid phase assays are by far the often increased specificity but lower sensitivity. most numerous and convenient. ELISA is the Near patient test kits are based either on latex most often used serological format. It is agglutination or immunochromatography. usually laboratory based, requiring both some Generally they have low sensitivities compared technical competence to perform and the with laboratory tests. Western blotting, ELISA, availability of an instrument to measure the and recombinant immunoblot assays (RIBA) optical density of the coloured product. Alter- have also been developed into commercially natively, latex agglutination tests are most available kits and can be used to indicate the suitable as near patient tests because they are presence of specific virulence markers. An technically simple to perform and provide a antigen detection kit has been developed for result within minutes rather than the hour or the detection of Helicobacter pylori in faeces. two for ELISA tests. In the technique for Immunological reagents have also been com- simultaneously detecting a serological re- bined with other diagnostic modalities to sponse to all antigens, represented by a single develop immunohistochemical stains and value of colour intensity (optical density) as in DNA immunoassays. the ELISA test, both the number and intensity of staining of antibody bound protein bands or Introduction antibodies to specific antigens are taken into http://gut.bmj.com/ Helicobacter pylori is now recognised as the account. A commercial western blot test cause of gastritis and most cases of peptic ulcer (Helicoblot 2) for the detection of H pylori is disease (PUD); its long term carriage increases also available. the risk of gastric adenocarcinoma sixfold and it is designated as a class I carcinogen.1 H pylori ELISA kits has also been implicated as a cause of gastric There have been many publications comparing 4–14 mucosa associated lymphoid tissue lympho- either single or multiple kits in defined on September 28, 2021 by guest. Protected copyright. mas. Its relation to non-ulcer dyspepsia re- populations. Tables 1 and 2 list the kits and mains controversial. Additionally, long term their reported sensitivity, specificity, and posi- Department of carriage of the organism may be associated tive and negative predictive values. Internal Medicine, with short stature in young girls and, in the University of Bologna, general population, as a possible risk factor for Latex agglutination kits Bologna, Italy the development of vasospastic disorders and The agglutination format is not as frequently D Vaira possibly skin immunopathology such as urti- used as the ELISA format but evaluations have M Menegatti caria. With the recognition of H pylori as an been published.15–21 The latex agglutination test C Ricci 2 F Landi important human pathogen, it has become is more convenient than the ELISA format for A Ali’ one of the growing number of organisms to near patient testing and has comparable sensi- L Gatta have its complete genome sequence mapped.3 tivity and specificity (table 3). C Acciardi Serology is an important method of deter- S Farinelli mining colonisation status and can be used for New immunological assays for H pylori M Crosatti diagnosis, as a screening procedure, or to S Berardi HISTOLOGY M Miglioli follow the eYcacy of eradication regimens. The use of stains such as the Giemsa stain to Most serological assays are in the ELISA detect H pylori in tissue sections relies on the Department of format although some are based on the latex experience of the histopathologist to recognise Bacteriology, agglutination reaction. These latter are used the typical morphological appearance of the University College principally as near patient assays. Most assays organism. Clearly, small numbers of organisms London Medical detect IgG in serum although some detect School, London, UK may be missed. Developments of current J Holton serum IgA. More recently developed assays detect IgA in saliva and the production of Abbreviations used in this paper: ELISA, enzyme Correspondence to: aYnity purified antibodies has led to the devel- linked immunosorbent assay; RIBA, recombinant Dr D Vaira, Clinica Medica opment of an antigen detection assay for faecal I, Università di Bologna, immunoblot assays; PUD, peptic ulcer disease; UBT, Policlinico S. Orsola, specimens. Serological reagents have also been urea breath test; RUT, rapid urease test; PCR, Bologna, Italy. used in immunocytochemistry and to speed up polymerase chain reaction. I24 Vaira, Holton, Menegatti, et al Table 1 Commercially produced serological assays for detection of Helicobacter pylori histological methods include the use of immu- infection nohistochemistry in order to increase both the sensitivity and specificity of the method. In a Kit name Kit name Test format Manufacturer Gut: first published as 10.1136/gut.45.2008.i23 on 1 July 1999. Downloaded from comparison of immunohistochemistry, using a Pyloristat Pylori Elisa II1 ELISA Biowhittaker, USA polyclonal antiserum, with the Giemsa and Pyloriset Pyloriset update ELISA Orion, Finland Helico G Helico G II ELISA Shield, UK Warthin-Starry stains, the method had a higher Premier Hp ELISA Meridian, USA specificity and a lower interobserver variation.22 Cobas Core ELISA Roche, Switzerland Immunocytochemistry also performs signifi- Hel-p Test Hel-p Test II ELISA Amrad, Australia MalaKit ELISA BioLab, Belgium cantly better compared with culture and biopsy GAP IgG GAP IgG II ELISA Biorad, USA urease test when small numbers of bacteria are Roche MTP ELISA Roche, Switzerland present and following eradication treatment.23 Hp-G screen ELISA Genesis, UK Microstar EIA ELISA Kenstar, UK Other histological developments include the SIA Helicobacter ELISA Sigma, USA fixing of the mucus layer using Carnoy’s HM-CAP EIA ELISA Enteric Prod., USA Helisal EIA ELISA Cortex, UK solution combined with immunohistochemis- Helori CTX ELISA Eurospital, Italy try, which reduces both the false positive and H pylori IgG ELISA Dako, Denmark negative results obtained with conventional Autozyme ELISA Cambridge LS, UK 24 Pyloragen ELISA Hycor, USA histological stains. Enzygnost HP ELISA Boehring, UK Quickvue HP EIA ELISA Quidel, USA PCR AND DNA-ENZYME IMMUNOASSAY Enzywell HP EIA ELISA Dresse Monteriggioni, Italy Color Vue Pylori ELISA Seradyn, USA Although most diagnostic PCR amplicons are Autoplate ELISA Menarini detected by gel electrophoresis, there is a Biolife ELISA Biolife growing trend towards using a colorimetric Pyloriset Pyloriset Dry LA Orion, Finland Helisal RBT Helisal One Step IMC Cortex, UK method of detection as this is more rapid and Flexsure HPS Flexsure WB IMC Smith-Kline, USA can be automated. Genesis Dot IMC Genesis, UK Three DNA enzyme immunoassays have Quickvue One Step IMC Quidel USA Launch Immunocard IMC Meridian, USA been developed to detect H pylori. The Quadratech HEP IMC VEDA, France GEN-ETI-K DEIA (Sorin, Italy) uses strepta- CLOser IMC Medical Inst. Corp., Switzerland vidin coated microwell plates to which is added HelicoBlot 2.0 WB GeneLab, Singapore RIBA WB Chiron, USA a biotinylated specific probe based on the UreC gene of helicobacter. The amplified product is LA, latex agglutination; IMC, immunochromatography; WB, western blotting. added to the plate and the duplex DNA detected with an enzyme linked antibody against double stranded DNA. PYLORI- Table 2 Comparison of commercially available ELISA kits for detection of Helicobacter pylori infection PROB (Biocode, Belgium) is a solid phase sandwich hybridisation assay. A specific cap- Kit name Sensitivity (%) Specificity (%) PPV (%) NPV (%) ture probe (also based on the UreC gene) is http://gut.bmj.com/ Pyloristat 91–99 70–94 80 84 bound to the microwell plate. The amplified Pylori Elisa II 100 96 97 100 product is added to the well and detected by a Helico G 71–97 65–95 69–90 65–98 biotinylated probe to which are added strepta- Helico G 2 85 76 84 87 Premier HP 85–100 80–100 76–100 88–100 vidin conjugated peroxidase and substrate. Cobas Core 87–98 83–98 87 86 PCR-ELISA (Boehringer, Germany) uses a Pyloriset 81–97 69–97 76–97 51–98 capture probe labelled with biotin (UreC) Pyloriset update 100 79 95 100 Hel-p Test 89–100 62–93 65–90 91–100 bound to the solid phase in a streptavidin Malakit 79–87 86–98 96 60 coated microwell plate to which is added the on September 28, 2021 by guest. Protected copyright. GAP IgG 76–100 26–99 76–100 71–100 amplified product labelled with digoxigenin HP kit Radim 81 90 Roche MTP 94–99 83–86 88 90 and the hybridised product is detected with HpG screen 83–93 68–91 66–84 84–100 anti-digoxigenin peroxidase. Microstar 97 76 80 98 Assessment of these three kits25 was per- SIA sigma 85–90 80–98 76–96 88–100 HM cap EIA 83–98 80–96 76 86 formed on biopsy specimens from 199 patients Autozyme89525887 and compared with PCR with gel electrophore- Pyloragen 79 75 71 83 sis and histology/culture as a gold standard. Enzygnost80747083 Quidel EIA 89 66 68 89 The colorimetric DNA immunoassays were Enzywell 90 71 71 91 100 times more sensitive than the standard ColorVue88666387 PCR and results were obtained within four PPV, positive predictive value; NPV, negative predictive value.