Comparison of ELISA antigen preparations alone or in combination for serodiagnosing Helicobacter pylori infections

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.

Increasing gastric juice pH level prior to anti-Helicobacter pylori therapy may be beneficial to the healing of duodenal ulcers

The aim of this study was to observe the efficacy of clarithromycin-based triple therapy for Helicobacter pylori (Hp)-infected duodenal ulcer when combined with different pH levels of gastric juices. A total of 160 patients with Hp-infected duodenal ulcers were randomly allocated into two groups. Patients in the treatment group (n=80) were administered a 20-mg dose of omeprazole twice daily for 1 week and then the treatment and control groups (n=80) received therapy for Hp infection and duodenal ulcers. We observed the ulcer healing stage, the content of anti-Hp IgA in gastric juice and the Hp eradication rate before and after proton pump inhibitor therapy in the two groups. Results revealed that the Hp eradication rate in the treatment group was 93% compared with 81% in the control group, and the difference was statistically significant (P<0.05). The ulcer healing rate in the treatment group was 93%, compared with 70% in the control group (P<0.05). A positive linear correlation was observed between gastric pH and the content of anti-Hp IgA in gastric juice (P<0.05). Increasing gastric pH prior to anti-Hp therapy may be beneficial to the eradication of Hp and for promoting the healing of duodenal ulcers.

Diagnostic methods for Helicobacter pylori detection and eradication

Helicobacter pylori is the principal cause of peptic ulcer disease and an important risk factor for the development of gastric cancer. The efficacy of 1 week triple therapies, which often have eradication rates of>90%, is undermined by poor patient compliance and bacterial antimicrobial resistance. The development of new anti-H. pylori therapies presents enormous challenges to clinical pharmacologists, not only in the identification of novel targets, but also in ensuring adequate drug delivery to the unique gastric mucus niche of H. pylori. Animal models of H. pylori infection have been developed but their clinical validity has yet to be established. Vaccination, to prevent or treat infection, has been demonstrated in animal models, but human studies have not been so encouraging.

Evaluation of two commercial enzyme immunoassays, testing immunoglobulin G (IgG) and IgA responses, for diagnosis of Helicobacter pylori infection in children

Serological testing to diagnose Helicobacter pylori infection in children is still controversial, although commonly used in clinical practice. We compared the immunoglobulin G (IgG) and IgA results of two commercially available enzyme immunoassays (EIAs) (Pyloriset IgG and IgA and Enzygnost II IgG and IgA) for 175 children with abdominal symptoms divided into three age groups (0 to < or =6 years, n = 47; >6 to < or =12 years, n = 77; >12 years, n = 51). A child was considered H. pylori infected if at least two of three tests (histology, rapid urease test, 13C-urea breath test) or culture were positive and noninfected if all results were concordantly negative. Of 175 children, 93 (53%) were H. pylori negative and 82 were H. pylori positive. With the recommended cutoff values, the overall specificity was excellent for all four EIAs (95.7 to 97.8%) regardless of age. Sensitivity varied markedly between tests and was 92.7, 70.7, 47.5, and 24.4% for Enzygnost II IgG, Pyloriset IgG, Enzygnost II IgA, and Pyloriset IgA, respectively. Sensitivity was low in the youngest age group (25 to 33.3%), except for Enzygnost II IgG (91.6%). Receiver-operating curve analyses revealed that lower cutoff values would improve the accuracy of all of the tests except Enzygnost II IgG. Measurement of specific IgA, in addition to IgG, antibodies hardly improved the sensitivity. The specificity of commercial serological tests is high in children when the cutoff values obtained from adults are used. In contrast, sensitivity is variable, with a strong age dependence in some, but not all, tests. We speculate that young children may have a different immune response to H. pylori, with preferable responses to certain antigens, as well as lower titers than adults. The Pyloriset test may fail to recognize these specific antibodies.

Accurate diagnosis of Helicobacter pylori. Serologic testing

Serologic testing is a useful noninvasive testing strategy for H. pylori. It is particularly useful in areas where the prevalence of H. pylori is high and inexpensive point-of-contact fingerprick tests are used. Sensitive tests are valuable ways of excluding H. pylori infection and can be used in conjunction with a direct test (urease histology culture or breath test) to confirm absence of H. pylori if the two methods are concordant. Serologic testing is more definitive and differentiating if the antigenic epitopes of H. pylori can be differentiated based on the antigenic epitopes that specifically associate with gastric cancer, peptic ulcer, and nonulcer dyspepsia. A study by Kawahara's group reported that Hsp 60 may be involved in the development of mucosa-associated lymphoid tissue based on ELISA. The idea of differentiating antigens for H. pylori may open a new area for use of serologic testing in the diagnostic approach of H. pylori infections.

Purification and characterization of neutral sphingomyelinase from Helicobacter pylori

Phospholipase activities of human gastric bacterium, Helicobacter pylori, are regarded as the pathogenic factors owing to their actions on epithelial cell membranes. In this study, we purified and characterized neutral sphingomyelinase (N-SMase) from the superficial components of H. pylori strains for the first time. N-SMase was purified 2083-fold with an overall recovery of 37%. The purification steps included acid glycine extraction, ammonium sulfate precipitation, CM-Sepharose, Mono-Q, and Sephadex G-75 column chromatography. Approximate molecular mass for the native N-SMase was around 32 kDa. When N-omega-trinitrophenylaminolauryl sphingomyelin (TNPAL-SM) was used as a substrate, the purified enzyme exhibited a K(m) of 6.7 microM and a V(max) of 15.6 nmol of TNPAL-sphingosine/h/mg of protein at 37 degrees C in 50 mM phosphate-buffered saline, pH 7.4. N-SMase reaches optimal activity at pH 7.4 and has a pI of 7.15. The enzyme activity is magnesium dependent and specifically hydrolyzed sphingomyelin and phosphatidylethanolamine. The enzyme also exhibits hemolytic activity on human erythrocytes. According to Western blot analysis, a rabbit antiserum against purified N-SMase from H. pylori cross-reacted with SMase from Bacillus cereus. Sera from individuals with H. pylori infection but not uninfected ones recognizing the purified N-SMase indicated that it was produced in vivo. In enzyme-linked immunosorbent assays, the purified N-SMase used as an antigen was as effective as crude protein antigens in detecting human antibodies to H. pylori.

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.

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.

Blood tests in the management of Helicobacter pylori infection. Italian Helicobacter pylori Study Group

There are three main types of blood test available for the management of Helicobacter pylori infection: those that detect an antibody response; tests of the pathophysiological state of the stomach; and those that indicate an active infection. Enzyme linked immunosorbent assay (ELISA) based kits are the most numerous of the commercially available tests. Originally the kits used crude antigen preparations but many of the newer kits use a more purified antigen preparation giving increased specificity but a lower sensitivity. The sensitivity, specificity, and predictive values of the tests can also be affected by the population under test and coexistent disease in the patients. Near patient test kits are based on either latex agglutination or immunochromatography. Generally, they have low sensitivities compared with laboratory tests. Commercial western blotting kits have also been developed and are used to detect the presence of specific virulence markers. The exact role of serology in the management of Helicobacter infection has still to be defined, although there is evidence that, used as a screening procedure, it can reduce endoscopy cost and workload. Gastrin and pepsinogen blood concentrations may provide valuable information on the pathophysiological state of the stomach--for example, the presence of inflammation or gastric atrophy. A combination of serology and serum concentrations of gastrin and pepsinogen may be used effectively to detect serious gastroduodenal disease in patients.

Helicobacter pylori does not play a role in the aetiology of acute appendicitis

The aetiology of acute appendicitis remains uncertain. H. pylori is viable outside the gastroduodenum, however its pathological role outside this area has not been fully investigated. Ten consecutive patients with a histological diagnosis of acute appendicitis were investigated for H. pylori status by serology, and by culture, histology, and polymerase chain reaction (PCR) analysis of the appendiceal specimens. One patient had positive serology for H. pylori, however PCR analysis was negative. Culture failed to reveal H. pylori colonies. Histology in 5 cases did reveal organisms with a morphological appearance of H. pylori, but PCR analysis confirmed that H. pylori was not present. Using a variety of methods, with PCR acting as the 'gold standard', we have shown that H. pylori is not associated with acute appendicitis.

Diagnosis of Helicobacter pylori

In view of its potential risk for the development of gastrointestinal disease or even gastric cancer at a later age, the study of Helicobacter pylori infection in childhood is gaining increasing importance and H. pylori infection is being considered a major issue of public health. H. pylori infection can be detected by a variety of methods. Because of its easy use, affordability, and overall availability, serology is the preferred diagnostic test, especially for large epidemiological studies. Based on our results, one might consider treating a child with recurrent abdominal pain and positive serology for H. pylori without further work-up, and only perform additional investigations when an anti-H. pylori therapy fails to resolve the complaints. According to this proposition, endoscopy of the upper gastrointestinal tract remains indicated in children if the noninvasive tests for Helicobacter pylori are negative in the absence of a diagnosis, or if symptomatology persists despite treatment.

IgG and IgA antibodies in Helicobacter pylori infections

We compared Helicobacter pylori-specific IgG and IgA antibodies in serum, salivary and gastric juice of H. pylori-infected and noninfected patients using the ELISA method. Serum and salivary anti-H. pylori IgG and IgA titres were higher in H. pylori-positive than H. pylori-negative patients. Serum H. pylori IgG titres were higher than those of serum-specific IgA. In contrast, H. pylori IgA titres in saliva samples were higher than those of specific IgG. In all patients, the levels of IgG antibodies were very low in gastric juice. H. pylori-positive patients with increased levels of IgA in sera, also exhibited increased IgA levels in gastric juice. The determination of IgA antibodies in serum and saliva may be used as a test that complements the IgG antibody assay.

Helicobacter pylori seropositivity in subjects with acute myocardial infarction

OBJECTIVE

To determine whether Helicobacter pylori infection increases the risk of myocardial infarction.

DESIGN

Case-control study.

SETTING

University teaching hospital.

METHODS

Serological evidence of H pylori infection was determined in 342 consecutive patients with acute myocardial infarction admitted into the coronary care unit and in 236 population-based controls recruited from visitors to patients on medical and surgical wards.

RESULTS

206/342 (60.2%) of cases were H pylori positive compared with 132/236 (55.9%) of controls (P = 0.30). Age and sex stratified odds ratio for myocardial infarction associated with H pylori seropositivity was 1.05 (95% CI 0.7 to 1.53, P = 0.87) and this remained non-significant (P = 0.46) when other risk factors for ischaemic heart disease were taken into account using logistic regression analysis. H pylori seropositivity was not associated with several coronary risk factors in either cases or controls.

CONCLUSION

No increase was found in H pylori seropositivity in subjects with acute myocardial infarction. This suggests that previous H pylori infection is not a major risk factor for acute myocardial infarction.

Diagnosis of Helicobacter pylori infection

A number of diagnostic tests have been developed for the detection of H. pylori. Diagnostic techniques can be divided into invasive and noninvasive methods. The invasive methods require upper gastrointestinal endoscopy and involve culture of gastric biopsy specimens, examination of stained biopsies and detection of urease activity in the biopsies themselves. In addition, we have developed endoscopic diagnosis of H. pylori infection in gastric mucosa using phenol red dye-spraying. The noninvasive methods include urea breath test and serological techniques. Although there has been considerable improvement in the techniques, a combination of at least two different techniques should be used in order to optimize the diagnostic yield. We recommend the use of one rapid test in the combination. The rapid urease test, cytology and the phenol red dye-spraying endoscopy give results available before the patient leaves the endoscopy suite.

Multi-laboratory comparison of eight commercially available Helicobacter pylori serology kits. Helicobacter pylori Serology Study Group

The performance of eight commercially available EIA kits in detecting antibody to Helicobacter pylori was evaluated by a panel of 17 laboratories using serum from 59 patients selected from endoscopy clinics in Belgium, Ireland, Italy, the Netherlands and Switzerland. Each laboratory received a randomly numbered set of sera and was ignorant of the culture results of the patients. The performance of the kits was assessed in terms of diagnostic accuracy compared to culture (measured by sensitivity and specificity), the inter-laboratory variability in diagnostic accuracy and the number of laboratories that experienced problems in using the kits. Grey zone results, which are routinely used to highlight the uncertain interpretation of results that lie near the cut-off point between positive and negative diagnoses, were accounted for in the analysis. Laboratories experienced practical problems in using some kits, whilst other kits were found to have high inter-laboratory variation or low diagnostic accuracy. There was no single kit that performed better on every criterion than the others. The Orion kit was a good all-round performer, whilst the Roche kit was excellent at detecting positive results, although it had a slightly raised false-positive rate.

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

Two novel commercial IgG enzyme immunoassay (EIA) systems based on acid-glycine-extracted (Pyloriset IgG EIA, Orion Diagnostica) or fast protein liquid chromatography-purified (Cobas Core Anti-H. pylori EIA, Roche Diagnostic Systems) Helicobacter antigens were evaluated in a prospective study involving 127 patients. All patients underwent upper endoscopy with biopsy, and biopsies were examined for the presence of Helicobacter pylori by a rapid urease test, microscopy and culture. Of the 71 patients found to be infected with Helicobacter pylori, 69 (97.2%) and 65 (91.5%) tested positive with the Cobas Core and Pyloriset test, respectively. A detailed receiver operating characteristic analysis of the two tests showed that the Cobas Core assay was more sensitive and specific at every possible cut-off level; gave a better resolution of individual results, indicating a greater fine-sensitivity; and had no grey zone compared to a large grey zone encompassing 13.4% of the serum samples tested with the Pyloriset EIA. The Cobas Core assay appears to be a valuable tool for epidemiological purposes as well as for pre-endoscopic screening of dyspeptic patients.

Serum antibody response to the superficial and released components of Helicobacter pylori

Superficial and released components were extracted from six selected Helicobacter pylori strains. The protein and antigenic profiles of these extracts were representative of the profiles found most frequently among the clinical strains and included major peptidic fractions at 19, 23.5, 57, 68, 76, 118, and 132 kDa and major antigens at 68, 57, and 23.5 kDa. Immuno-cross-reactions were seen with a hyperimmune rabbit serum to Campylobacter fetus but not with sera to Campylobacter jejuni or Salmonella spp. An antigenic preparation was obtained by pooling equivalent quantities of each extract, and the antigenic preparation was used to study the antibody responses of sera from 65 French patients and 127 Tunisian patients. By enzyme-linked immunosorbent assay, we observed that the sera from French and Tunisian patients clustered into two populations, defined as antibody positive (72 patients) and antibody negative (120 patients). The antibody-positive patients were more frequently infected with H. pylori (P < 0.01) and were more frequently affected with gastritis (P = 0.05). However, no correlation between antibody levels and clinical signs of dyspepsia was noticed. The proportions of antibody-positive patients were similar in France and Tunisia. Antibody-positive and antibody-negative sera were studied by western blot (immunoblot) analysis. The antibody-positive sera revealed an average of 7.7 antigenic bands, whereas the antibody-negative sera revealed an average of 2.4 antigenic bands (P < 0.01). The antigens between 15 and 40 kDa and greater than 66 kDa were specifically recognized by the antibody-positive sera, although in this molecular size range the antibody profiles of these sera exhibited a fairly high degree of diversity. We conclude that the superficial and released components from H. pylori contain a variety of bacterial immunogens and may be useful in antigenic preparations for the serodiagnosis of H. pylori infections. Moreover, a group of antigens in combination appears to be useful for discriminating antibody-positive and antibody-negative patients.

Systemic and mucosal humoral responses to Helicobacter pylori in gastric cancer

The systemic IgG response to Helicobacter pylori was examined in 70 patients with gastric cancer. H pylori IgG antibodies were assayed by enzyme linked immunosorbent assay (ELISA), and serological recognition of H pylori antigens was characterised by western blotting. A percentage of 78.5 were seropositive by ELISA. Two of five patients under age 50 were seronegative. Positivity was unrelated to age, sex, tumour type, or site. Ninety one per cent of ELISA positive cancer patients recognised the H pylori cytotoxin associated 120 kilodalton (kD) protein, significantly more than a control group of 47 ELISA positive patients with non-ulcer dyspepsia (72%). Four of 15 ELISA negative cancer patients also showed recognition of this protein in western blots. Mucosal IgA responses to H pylori were examined by immunoblotting supernatants of in vitro cultured resected antral mucosa in an overlapping group of 19 gastric cancer patients. Eighteen had a positive response, including 10 of 11 negative for H pylori by biopsy urease testing. The systemic and local immunoblotting results show that the high seroprevalence of H pylori antibodies detected by ELISA is nevertheless an underestimate of past infection. Dyspepsia screening policies based solely on H pylori ELISA would miss some young patients with gastric cancer. Further study of the relation of the H pylori cytotoxin to gastric precancerous lesions is warranted.

Helicobacter pylori antibodies in sera of children suffering from chronic abdominal pain

107 pediatric patients aged 9 to 18 with persistent gastric complaints were examined serologically and bacteriologically for Helicobacter pylori. Helicobacter was identified in 48 (45%) of individuals. 51 (48%) of children were found to be seropositive when H. pylori antibodies were detected by the ELISA; 56 (52%) when the passive haemagglutination test was used, and 41 (38%) in the latex agglutination test. 25% of culture-negative patients were found to be seropositive. The percentage of raised H. pylori antibody titres in the control (healthy subjects) varied from 20 to 27%, depending on the method applied.

Evaluation of a commercial latex test for serological diagnosis of Helicobacter pylori infection in treated and untreated patients

The value of a commercially available latex test (Pyloriset) for the diagnosis of Helicobacter pylori infection by demonstration of specific antibodies was compared with that of direct diagnostic methods such as culture, biopsy-urease test and microscopy of fuchsin-stained smears. The sera were from 136 patients who prior to this study either had or had not been treated for Helicobacter pylori-infection simultaneously with amoxicillin (3 x 750 mg/day) and metronidazole (3 x 500 mg/day) for 12 days. On average, the sensitivity of the test was 90%. The specificity with sera from untreated patients was 75.9%; with sera from treated patients specificity was 22.2%, 28% and 20% 1, 3 and 6 months respectively after start of treatment. Only as late as one year after the onset of chemotherapy did the specificity return to 67%. Because of its low specificity this test does not offer any advantage over other tests in the detection of Helicobacter pylori-infection or in monitoring the chemotherapeutic success.

Serodiagnosis of Helicobacter pylori: comparison of enzyme-linked immunosorbent assays

Enzyme-linked immunosorbent assays (ELISAs) have been developed to diagnose Helicobacter pylori infection. However, the methods are not standardized. We therefore prospectively evaluated the sensitivities and specificities of ELISAs developed in the United States and the United Kingdom in a study population comprising 41 consecutive symptomatic outpatients and 35 volunteers. At endoscopy, multiple biopsies were obtained for histology and culture and stained sections were graded for chronic gastritis, active chronic gastritis, and density of H. pylori. Serum samples were analyzed for H. pylori by ELISA. The first set of assays for immunoglobulin G (IgG) and IgA used a pool of sonicated isolates of H. pylori from five patients in the United States (antigen A). The second set of assays, developed in the United Kingdom, used three different antigens: antigen 1, an acid-extractable surface antigen; antigen 2, an acid-extractable antigen from an aflagellate variant; and antigen 3, a urease-containing fraction. Cutoff scores for positive results were determined a priori on the basis of previous serological studies. There was close agreement between histology and culture. In the study population, 36% of the individuals were H. pylori positive. The diagnostic value of the different ELISAs were highly comparable, and the crude antigens performed as well as the more purified antigens. The antigen A IgG had a sensitivity and specificity of 96 and 94%, respectively; the values for antigen 1 were 93 and 96%, respectively. The antigen A IgA and antigen 3 assays were the least sensitive tests.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of a commercial ELISA for serodiagnosis of Helicobacter pylori infection

A commercial ELISA for the detection of Helicobacter pylori IgG antibodies was evaluated using serum from 242 patients attending an endoscopy clinic. The efficacy of the ELISA was assessed in relation to the histological detection of H pylori on antral mucosal biopsy specimens. In patients under 61 years of age (n = 138) the ELISA was 97.5% sensitive and 85.5% specific for H pylori infection, with a positive predictive value of 91% and a negative predictive value of 96%. Over the whole group the sensitivity of the ELISA was 93.8% and the specificity 79.3%. The positive predictive value and negative predictive values were, respectively, 90% and 87%. These results suggest that the Bio-Rad GAP IgG H pylori ELISA is suitable for serodiagnosis of H pylori infections for most clinical purposes and thus makes H pylori serology available to routine diagnostic laboratories.

Helicobacter pylori: histological and serological study on gastric and duodenal ulcer patients in Estonia

We have examined the occurrence of Helicobacter pylori (HP) infection in 86 Estonian gastric ulcer (GU) and 25 duodenal ulcer (DU) patients. Diagnosis of the HP infection was made histologically (modified Giemsa) from gastric biopsy specimens, and serologically by parallel use of two enzyme-linked immunosorbent assays for IgG antibodies to HP in patient sera. The infection was diagnosed simultaneously by all three methods in 84% of the GU and 84% of the DU patients. The infection was revealed histologically in 88% of the GU and 92% of the DU patients, and serologically by either of the two methods in 94% and 92% of the GU and DU patients, respectively. HP infection was absent by all three methods in one GU patient only, this patient being the only subject who showed normal gastric mucosa in conventional histology. These observations show that HP infection is very common in patients with peptic ulcer in Estonia. In addition, the findings suggest that the serological assays will find a small proportion (15%) of ulcer patients with antibodies against HP but no histologically detectable bacteria.

Antigenicity of fractions of Helicobacter pylori prepared by fast protein liquid chromatography and urease captured by monoclonal antibodies

The antigenicity of Helicobacter pylori protein fractions separated by fast protein liquid chromatography size exclusion was investigated by EIA with sera from patients of well defined Helicobacter pylori status. The antigenic material of Helicobacter pylori was confined to fractions 8 and 14 to 21. Urease containing fractions (14/15) and flagella containing fractions (17/18) were identified. Fraction 8 non-specifically bound human immunoglobulin as demonstrated by the binding of Helicobacter pylori negative sera. The remaining fractions 14 to 21 when used individually as EIA antigens were 91-100% specific, however fractions 16 to 19 showed a reduced sensitivity (78%) compared with the acid extract (95%). The urease fractions were 91% sensitive. Purified urease antigen captured by antiurease monoclonal antibodies was 83% sensitive and 93.3% specific.