Alan F. Cutler

Accuracy of invasive and noninvasive tests to diagnose Helicobacter pylori infection

BACKGROUND & AIMS Multiple tests are available for determining Helicobacter pylori infection. Our aim was to compare the sensitivity, specificity, and negative and positive predictive value of the most widely available tests for diagnosis of H. pylori. METHODS A total of 268 patients (mean age, 53.7 +/- 15.8 years; 142 male and 126 female; 125 white and 143 nonwhite) was tested for H. pylori infection by [13C]urea breath test (UBT), measurement of serum immunoglobulin (Ig) G and IgA antibody levels, and antral biopsy specimens for CLO test, histology, and Warthin-Starry stain. No patient received specific treatment for H. pylori before testing. The infection status for each patient was established by a concordance of test results. RESULTS Warthin-Starry staining had the best sensitivity and specificity, although CLO test, UBT, and IgG levels were not statistically different in determining the correct diagnosis. The absence of chronic antral inflammation was the best method to exclude infection. Stratification of results by clinical characteristics showed that UBT and chronic inflammation were the best predictors of H. pylori status in patients older than 60 years of age. IgA was a better predictor in white patients. CONCLUSIONS The noninvasive UBT and IgG serology test are as accurate in predicting H. pylori status in untreated patients as the invasive tests of CLO and Warthin-Starry.

Use Caution with Serologic Testing for Helicobacter pylori Infection in Children

Commercial serologic assays accurately detect adult Helicobacter pylori infection. Their use in children remains controversial. An ELISA to detect H. pylori IgG in children was developed and compared with three commercial assays. ELISA standardization was done with sera from all ages and validation was done with another cohort of sera with known H. pylori status. Three commercial serologic assays were subsequently compared against this pediatric ELISA at independent sites, at which 142 pediatric serum samples from different countries were evaluated. The pediatric ELISA was 91.4% sensitive. Assay 3 demonstrated a sensitivity of 78%. Less sensitivity was observed for assay 1 (70%) and assay 2 (63%). Accuracy of commercial assays was greatly reduced when sera from developing countries and younger ages were evaluated. Results of serologic tests used to diagnose H. pylori should be interpreted with caution when evaluating children with abdominal pain. Accurate serologic assays in children may be more important for epidemiologic research than for clinical decision making.

FOUR-YEAR TRENDS IN HELICOBACTER PYLORI IGG SEROLOGY FOLLOWING SUCCESSFUL ERADICATION

PURPOSE Detection of anti-Helicobacter pylori antibodies is accurate in the diagnosis of the infection, and there is a decline in IgG titers after successful eradication. It is not known whether these titers continue to decline during the next 3 to 4 years. PATIENTS AND METHODS Patients had been successfully treated for H pylori with triple therapy (metronidazole, tetracycline, and bismuth subsalicylate) during 1990 and 1991. Those who had frozen serum samples available from that time were contacted to have follow-up serum collected in 1994. A simultaneous [13C]urea breath test was done to confirm H pylori infection status. Serology was determined by quantitative enzyme-linked immunosorbent assay (ELISA) and qualitative immunoassay. RESULTS All 29 patients who agreed to participate were free of H pylori infection. They had a mean decrease in H pylori IgG titers of 51% from baseline (P <0.001). Titers remained stable from 1 year to a mean of 3.5 years after therapy (range 2.8 to 4.4). Of the 29 patients, 21 (72%) remained seropositive by ELISA 3.5 years after successful H pylori treatment, and 18 (62%) remained positive by rapid serum immunoassay. CONCLUSION IgG titers against H pylori plateau at a 50% decrease after therapy. Helicobacter pylori serology, either quantitative or qualitative, will yield false positive results in patients who have previously been treated for H pylori and should not be used to determine infection status in this population.

Role ofHelicobacter pylori serology in evaluating treatment success

Duodenal ulcer recurrence and gastritis are reduced with successfulHelicobacter pylori treatment. Serology is accurate in the diagnosis ofH. pylori, but its value in determining eradication is unproved. To evaluate the usefulness of serology in monitoring treatment, we measured serial serum antibodies in three patient groups: eradication success (N=57), eradication failure (N=19), and untreated patients (N=24). Eradication was determined by Warthin Starry staining of antral biopsies and repeat13C breath tests at six weeks. Subsequent13C breath tests were then performed at three-month intervals to monitor eradication. IgG antibody concentrations toH. pylori were determined by a commercially available ELISA kit. Serology concentrations remained constant throughout the study period in the untreated patients. IgG concentrations decreased slightly in the treatment failure group at six weeks but thereafter remained at baseline values. In the eradicated group, serum IgG concentrations decreased 26% by three months, 43% by six months and 55% at nine and 12 months (P<0.001). A 20% reduction in IgG concentrations by six months was associated with successful treatment (sensitivity 86% and specificity 88%). We conclude that serology is a potentially useful way to monitorH. pylori treatment success.

Value of Serology as a Noninvasive Method for Evaluating the Efficacy of Treatment of Helicobacter pylori Infection

The systemic humoral response to Helicobacter pylori was studied in 86 infected adult patients before antimicrobial therapy and at intervals following therapy. Endoscopy with collection of biopsy specimens was performed immediately before treatment; a 13C-labeled urea breath test was performed, and blood specimens were collected before treatment and at 1, 3, 6, 9, and 12 months after treatment. Serum samples from three patient groups (eradication success [n = 50], eradication failure [n = 16], and no treatment [n = 20]) were assayed for IgA and IgG antibodies to H. pylori by enzyme-linked immunosorbent assay. Levels of antibody to H. pylori before treatment were similar in all three groups. As expected, the no treatment and eradication failure groups had no significant changes in antibody levels during the study period. In contrast, for the eradication success group, the specific IgA and IgG antibody levels decreased progressively and significantly. We conclude that serology is a potentially useful way to monitor the success of treatment of H. pylori infection without using invasive or more expensive methods.

Prospective evaluation of a new urea-membrane test for the detection of Helicobacter pylori in gastric antral tissue

AIM To determine the sensitivity, specificity, and positive and negative predictive values of a newly developed urea-membrane test for the detection of Helicobacter pylori in gastric tissue. METHODS Patients presenting for upper endoscopy with no recent exposure to H. pylori-altering drugs were enrolled. Antral biopsy specimens were tested by the urea-membrane and urea-gel methods and submitted for histology. Patients underwent [13C]urea breath tests. Presence of H. pylori was established by histology or the combination of a positive [13C]urea breath test and a positive urea-gel test. Absence of H.pylori required both the [13C]urea breath test and the invasive tests to be negative. The urea-membrane test was reported at 1 hour. RESULTS Ninety-nine patients (47 men and 52 women) with a mean age of 51.43 +/- 14.9 years participated. Fifty of 99 patients (prevalence, 50.5%) tested positive for H. pylori. The urea-membrane test correctly identified 49 of 50 H. pylori-positive and 46 of 49 H. pylori-negative patients, yielding sensitivity, specificity, and positive and negative predictive values of 98.0%, 93.9%, and 94.2% and 97.9%, respectively, in this population. CONCLUSIONS Rapidly available and reliable results from the urea-membrane test can facilitate clinical decision prior to patient discharge from the endoscopy suite.

Characteristics of Helicobacter pylori infection in Jamaican adults with gastrointestinal symptoms.

ABSTRACT Helicobacter pylori infection is common in Jamaica. Describing its epidemiology in a population-based study depends largely on serology, but serologic assays have not been validated in this population. To address this issue, we examined the presence ofH. pylori infection in 30 sequential adult patients with gastroduodenal symptoms by three biopsy-based methods (rapid urease test, histology, and culture) as well as by one research and two commercial enzyme-linked immunosorbent assays (ELISAs). A patient was considered H. pylori positive if the organism was detected by at least one biopsy-based method. Eighteen (60%) of the 30 patients were H. pylori positive by these criteria, whereas 21 (70%) were seropositive for H. pyloriimmunoglobulin G by our research ELISA. The presence of H. pylori infection in patients with gastric cancer and those with chronic gastritis was missed by biopsy-based methods but was detected by serologic assays. This observation indicates that serologic assays may be better suited for the detection of this infection in a population in which H. pylori-associated pathology is prevalent. The performance of our research ELISA in detecting biopsy-based H. pylori-positive cases was excellent, with a sensitivity and specificity of 100% and 75%, respectively. Molecular genotyping of the isolates revealed that the predominant H. pylori genotypes in this cohort of Jamaicans were cagA+ vacA slb-m1, andiceA2. The validated serologic assay enables us to interpret epidemiologic data from population-based studies in Jamaica by comparison to those from other populations.

Quantitative noninvasive testing for Helicobacter pylori does not predict gastroduodenal ulcer disease

BACKGROUND Helicobacter pylori is strongly associated with gastric and duodenal ulcer disease. However, the diagnosis of gastroduodenal ulcers requires an endoscopic or radiographic examination. In this study, we attempted to establish a relationship between the magnitude of [13C]urea breath test results or serum H. pylori IgG levels and endoscopic findings in H. pylori-infected individuals. METHODS Patients who had undergone endoscopy and had a positive [13C]urea breath test and/or positive H. pylori IgG serology were identified. Endoscopic diagnoses included duodenal ulcer, gastric ulcer, nonulcer dyspepsia, and others. Results of 6% or greater on the [13C]urea breath test was defined as positive for H. pylori infection. H. pylori IgG serology was determined by an enzyme linked immunosorbent assay with values of greater than or equal to 1.0 being seropositive. RESULTS One hundred seventy-five patients were seropositive (mean = 3.01 +/- 1.58). One hundred sixty-eight patients had a positive [13C]urea breath test (mean = 25.43 +/- 16.90). One hundred fifty-five patients were common to both the groups. Statistical analysis did not reveal any relationship between quantitative [13C]urea breath test results or H. pylori IgG values and endoscopic diagnoses. CONCLUSION The magnitude of [13C]urea breath test or H. pylori IgG serology cannot be used to predict the presence or absence of gastroduodenal ulcer disease.

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.

Admixture with whole blood does not explain false-negative urease tests.

Rapid urease test sensitivity for Helicobacter pylori is reduced in the presence of active upper gastrointestinal bleeding. The aim of this study was to evaluate the in vitro effect of whole blood on rapid urease testing. Urease solution was added to normal saline, and heparinized whole blood both positive and negative for H. pylori antibody. The mixtures were then serially diluted in saline, and/or whole blood and added to three different rapid urease kits. The admixture of urease in H. pylori-seropositive whole blood diluted in either saline or whole blood enhanced performance in both kits fourfold compared with saline alone. No false-negative results were observed in either kit. Seronegative whole blood produced similar results. Undiluted saline or whole blood produced no positive rapid urease tests. Whole blood accelerates the urease reaction in vitro. Neither H. pylori antibody-positive nor -negative whole blood adversely impacted the rapid urease test. False-negative rapid urease test results in upper gastrointestinal bleeding cannot be explained by admixture with whole blood.