Analysis of the 13C-urea breath test for detection of Helicobacter pylori infection based on the kinetics of Δ-13CO2 using laser spectroscopy

We have previously reported on laser spectroscopy as a simple alternative to mass spectrometry. To validate a simplified ¹³C-urea breath test (UBT) with laser spectroscopy for the detection of Helicobacter pylori in clinical use, we evaluated the optimal time of breath sample collection. The ¹³C-UBT was carried out on each of 102 infected and 70 non-infected subjects (32 without eradication and 38 after eradication therapy). Breath samples were taken at five time points within 60 min followed by 100 mg of ¹³C-urea administration. The ratio of ¹³CO₂ to ¹²CO₂ was measured using laser spectroscopy and the recovery of tracer in the exhaled breath was calculated. Results were compared with histological and culture examinations of gastric biopsies to establish the infection status. For statistical evaluation of ¹³C-UBT, the optimal timing of breath sample collection was examined on the basis of the kinetics of Δ-¹³CO₂. In 32 H. pylori-negative patients (without therapy), the mean ± 2SD of Δ-¹³CO₂ was at its minimum 20 min after urea ingestion whereas in H. pylori-positive patients, the mean ± SD Δ-¹³CO₂ was maximum at 20 min. In addition, receiver operating characteristic (ROC) curve analysis showed that the cut-off value was estimated between 2.5–3.0 per mil (‰) at 20 min before therapy. Based on the histology and culture results, the sensitivity, specificity and positive and negative predictive values were 98.0%, 100%, 100% and 94.1%, respectively. In conclusion, ¹³C-UBT with laser spectroscopy is a non-invasive, simple, sensitive and specific test to determine H. pylori status. Our findings suggest that in clinical use, measurements made at 20 min after substrate administration could be recommended for most sensitive and specific ¹³C-UBT results.     

Clinical significance of oral urease in diagnosis of Helicobacter pylori infection by [13C]urea breath test

This study was performed to evaluate the effect of oral flora on [¹³C]urea breath test in detecting H. pylori infection and find an optimal method and timing for sample collection. Forty-five volunteers were included in this study. The [¹³C]urea breath test was performed using mouthwash, endoscopic administration, and conventional methods. According to the receiver-operating characteristic curves, the earliest optimal time for discriminating H. pylori-positive and H. pylori-negative patients was at 25 min with the mouthwash method with 78% sensitivity and 82% specificity, at 2 min with the endoscopic administration method with 100% sensitivity and 100% specificity, and at 6 min with the conventional method with 100% sensitivity and 95% specificity. The study shows a significant effect of oral urease on the results of the [¹³C]urea breath test. The timing of sampling collection can be shortened to 6 min with the conventional method or to 2 min through endoscopic administration.     

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. (Gastrointest Endosc 1996;44:679-82.)     

Significance of an exaggerated meal-stimulated gastrin response in pathogenesis of Helicobacter pylori-negative duodenal ulcer

The aim of this study was to clarify the pathogenesis of Helicobacter pylori-negative duodenal ulcer (DU) by investigating the meal-stimulated serum gastrin (SG) response. The subjects were 9 patients with H. pylori-negative DU, 28 H. pylori-positive DU, 11 H. pylori-positive volunteers, and 30 H. pylori-negative volunteers. Blood samples were taken before and after consumption of a test meal. The integrated 1-hr gastrin response (IGR) was taken to be the area under the SG time curve, calculated by the trapezoid method. H. pylori infection status was determined by histology, serology, and the [¹³C] urea breath test. The mean basal SG concentration was lower in the H. pylori-negative DU patients than in the H. pylori-positive DU patients, but an exaggerated IGR was observed in three patients (33.3%) with H. pylori-negative DU. In conclusion, our findings indicate that an exaggerated meal-stimulated gastrin response may contribute to the pathogenesis of H. pylori-negative DU.     

Breath sample collection through the nostril reduces false-positive results of C-urea breath test for the diagnosis of Helicobacter pylori infection

Background. One of the disadvantages of ¹³C-urea breath test is possible interference by urease activity not related to Helicobacter pylori.Aims. We design the simple and non-invasive modification to avoid the contamination of ¹³CO₂ produced in the mouth.Patients and methods. One hundred and twenty-nine patients who underwent diagnostic upper endoscopy were enrolled. Within 1 week of the endoscopic procedure, each patient received the modified ¹³C-urea breath test. Breath samples were collected at baseline and at 1, 3, 5, 10, 15, 20 and 30 min after ingestion of 100 mg ¹³C-urea solution through the mouth and the nostril at each time point.Results. The breath Δ¹³CO₂ value through the nostril at 1 min was already higher in H. pylori-positive patients than in H. pylori-negative patients. Using 2.5‰ as the cut-off value, the sensitivity and specificity of the modified ¹³C-urea breath test at 20 min were both 100%, whereas the sensitivity and specificity of the standard ¹³C-urea breath test were 97.7 and 94%, respectively, using 3‰ as the cut-off value.Conclusions. The modified ¹³C-urea breath test in which breath samples are collected through the nostril provides an easy way of avoiding false-positive results for the detection of H. pylori infection.     

Accuracy of Stool Antigen Test in Posteradication Assessment of Helicobacter pylori Infection

Our aim was to evaluate the accuracy of HpSA test in the diagnosis of Helicobacter pylori infection after the end of eradication therapy. In all 106 H. pylori-positive patients (55 men and 51 women, mean age 51 years, range 19–82) were treated with a course of eradicating regimen. [¹³C]Urea breath test (UBT) and HpSA were performed four weeks after stopping the treatment. The diagnostic accuracy of HpSA was evaluated in comparison with the results of [¹³C]UBT. In 90 patients (85%) H. pylori was eradicated according to [¹³C]urea breath test. After eradication, sensitivity of HpSA was 87.5%, specificity 95.5%, positive predictive value 77.8%, negative predictive value 97.7%, and diagnostic accuracy 94.3%. HpSA is a valuable test in the posteradication assessment of H. pylori infection.     

[14C]Urea Breath Test Is Not Sensitive for Detection of Acute Helicobacter pylori Infection in Rhesus Monkeys (Macaca mulatta)

The urea breath test is sensitive and specific for detection of chronic infection with H. pylori. We sought to determine the sensitivity of the [¹⁴C]urea breath test for detection of acute H. pylori infection using experimentally infected rhesus monkeys. Eighteen monkeys were inoculated with H. pylori. Serial [¹⁴C]urea breath tests and cultures of gastric biopsies were performed before and up to 10 weeks after inoculation. Cultures from all 18 monkeys were positive for H. pylori at each time point. The sensitivity of the [¹⁴C]urea breath test increased systematically from 43% at two weeks after inoculation up to 93% at 10 weeks after inoculation. Quantitative cultures of H. pylori showed a tendency to decline over time following inoculation. We conclude that the [¹⁴C]urea breath test is not sensitive for detection of acute H. pylori infection in rhesus monkeys until 10 weeks after inoculation. While this may reflect a gradual increase in bacterial load that was not detected by limited sampling, our data are not consistent with this hypothesis.     

Helicobacter pylori Recurrence and Infection Rate in Israeli Adults

Introduction In developing countries the recurrence rate of Helicobacter pylori after successful eradication therapy is as high as 42%, while in developed countries it is estimated to be less than 3%. Such figures are very important in terms of determining clinical strategy and outcome. Aim To estimate the recurrence rate of H. pylori in Israel using the database of the "Central H. Pylori Laboratory of Clalit Health Services". Methods The database was searched for patients who had undergone the [¹³C]-urea breath test ([¹³C]-UBT) for validation of the successful eradication of H. pylori or for evaluation of dyspepsia 7 years previously and for whom the result had been negative. These patients were invited to participate in the trial, fill a symptom questionnaire and undergo another [¹³C]-UBT. Results A In total, 65 patients participated; of these, 26 patients had tested negative in the first ¹³CUBT, indicating the successful eradication of H. pylori (Group A), and 39 had been tested for dyspepsia (Group B). One patient in each group had a positive [¹³C]-UBT – 3.84% in Group A and 2.56% in Group B (non-significant difference, NS). The mean annual H. pylori recurrence rate was calculated to be 0.55% and 0.37% in Group A and Group B patients, respectively (NS). Conclusion Our results shown a very low re-infection or new infection rates in Israeli adults and are in line with other trials in developed countries; they do not support the a retesting program for patients after a successful eradication therapy.     

Gastric emptying andHelicobacter pylori infection in duodenal ulcer disease

The pathogenetic link betweenHelicobacter pylori gastritis and duodenal ulcer is still unknown. Fast gastric emptying of liquids might be important in the pathogenesis of gastric metaplasia of the duodenum and duodenal ulcer through an increased exposure of the duodenum to gastric acid. InH. pylori-infected subjects, an abnormal gastric emptying could affect urea breath test results and correlate with the histological gastritis. This study was performed to evaluate the gastric emptying of liquids in duodenal ulcer patients withH. pylori infection and the possible relation between the bacterial load, gastric emptying, and urea breath test results. Seventeen duodenal ulcer patients withH. pylori gastritis and 15 healthy volunteers were studied by a combined [¹⁴C]octanoic acid and [¹³C]urea breath test to evaluate gastric emptying rate andH. pylori status simultaneously. Endoscopy with antral biopsies was performed in all duodenal ulcer patients. Duodenal ulcer patients withH. pylori infection have a normal liquid gastric emptying that is unrelated with the histological severity of gastritis. The urea breath test results and the gastric emptying parameters do not correlate with histology. A significant correlation between the gastric emptying and the urea hydrolysis rate is found. It is concluded thatH. pylori infection in duodenal ulcer patients is not associated with abnormally fast liquid gastric emptying, and this finding should be taken into account when a causal link betweenH. pylori infection and duodenal ulcer disease is searched for. The correlation between gastric emptying and urea hydrolysis rate explains why no conclusions on intragastric bacterial load can be drawn from the urea breath test results.This study was presented in part as an oral communication at the Annual Meeting of the American Gastroenterological Association, May 1994, New Orleans, and published in abstract form inGastroenterology 106:A160, 1994.     

Helicobacter pylori infection reduces intraluminal nitric oxide in humans

It has recently been demonstrated that nitric oxide (NO) is highly concentrated in the gastric lumen and plays an important role in defending against pathogenic microorganisms in the stomach. NO in the gastric lumen is mainly delivered by extrinsic sources from saliva. We studied whether Helicobacter pylori infection affected intraluminal NO levels in humans. H. pylori infection was diagnosed on the basis of histology and culture or (¹³C)-urea breath test. Air and gastric juice in the gastric lumen were collected endoscopically. The concentration of intraluminal NO was measured by a chemiluminescence system, using an NO analyzer. The concentration of nitrite in gastric juice was measured by the Griess reaction. The intraluminal concentration of NO in H. pylori-positive patients (198.2 ± 41 parts per billion [ppb] mean ± SE; n = 70) was significantly lower than that in H. pylori-negative patients (353.0 ± 57.9 ppb; n = 43; P < 0.05). In contrast, the concentration of nitrite in gastric juice in H. pylori-positive patients (57.7 ± 12.3 μM; n = 70) was significantly higher than that in H. pylori-negative patients (25.9 ± 6.4 μM; n = 43, P < 0.01). The intraluminal concentration of NO in H. pylori-positive patients was markedly increased and the concentration of nitrite in H. pylori-positive patients was markedly decreased following the completion of eradication therapy. Based on these results, we propose that a decrease in NO and excess nitrite production in the gastric lumen are associated with H. pylori infection and may play an important role in the pathogenesis of H. pylori-related abnormalities. Received: December 14, 1998 / Accepted: June 25, 1999     

Accuracy of a monoclonal antibody-based stool antigen test in the diagnosis of Helicobacter pylori infection

Background: Recent availability of tests for Helicobacter pylori antigens in stool samples has provided potentially useful tools for epidemiological studies and clinical settings. The aim of this study was to evaluate a monoclonal antibody-based H. pylori antigen stool test in the primary diagnosis of H. pylori infection, and to study the test performance after patients were treated with lanzoprazole, and after eradication therapy. Methods: The study included 122 dyspeptic patients. At gastroscopy, biopsy specimens were obtained for culture and histology. Stool antigen and [[Formula: See Text]C]-urea breath tests were performed concurrently. Positive culture alone or a positive [[Formula: See Text]C]-urea breath test in combination with positive histology defined the reference standard. Forty-three Hp +ve patients were treated with lanzoprazole for 2 to 4 weeks, and stool antigen tests were performed on days 1 and 7 post-treatment. After eradication therapy, 32 patients were re-examined for H. pylori infection. Results: Prevalence of H. pylori was 44.3%. Sensitivity and specificity for the stool antigen test in the primary diagnosis of H. pylori infection were 98% and 94%, with positive and negative likelihood ratios of 16.7 and 0.02, respectively. All patients had positive stool tests immediately after lanzoprazole treatment, whereas 2 patients had negative stool tests after 7 days. Triple therapy rendered all patients stool test negative. Conclusions: The monoclonal antibody-based stool antigen test is an accurate tool in the primary diagnosis of H. pylori infection and after eradication therapy. Lanzoprazole treatment does not influence the clinical performance of the test.     

Breath ammonia measurement in Helicobacter pylori infection

Our aim was to define the utility of breath ammonia measurement in assessing Helicobacter pylori infection. Volunteers breathed into a device containing three fiberoptic NH₃ sensors at baseline and after ingesting 300 mg of urea. Breath ammonia levels were compared to the [¹⁴C]urea breath test. Thirteen subjects were tested. Before urea ingestion, H. pylori-positive subjects had significantly lower breath ammonia levels than negative subjects (mean ± sd, 0.04 ppm ± 0.09 vs 0.49 ppm ± 0.24, P = 0.002) and had a significantly greater increases in breath ammonia after urea ingestion (range 198–1494% vs 6–98%). One H. pylori-positive subject underwent treatment and breath ammonia levels shifted from the pattern seen in positive subjects to that seen in negative subjects. In conclusion, breath ammonia measurement for H. Pylori-positive and negative subjects showed distinct patterns. Breath ammonia measurement may be feasible as a diagnostic test for H. pylori.     

A Simple,Rapid, and Highly Reliable Capsule-based 14C Urea Breath Test for Diagnosis of Helicobacter pylori Infection

Background: Since the urea breath test (UBT) indirectly detects gastric Helicobacter pylori infection by measuring urease activity, the possibility of false-positive results due to other urease-producing bacteria cannot be excluded. Previous studies have shown that increased ¹⁴CO₂ activity in early breath samples could be attributed to urea hydrolysis in the oropharynx. For that reason, reliable assessment of H. pylori status is hampered for at least 20 min after administration of a ¹⁴C-urea drink. Methods: To overcome this problem, we have developed a modified breath test in which 111kBq ¹⁴C-urea is supplied in a gelatin capsule, which prevents release of ¹⁴C before reaching the stomach. Our modified ¹⁴C UBT was evaluated in 100 healthy volunteers, and results were compared with those from enzyme-linked immunosorbent assay serology. Results: The study showed a 99% concordance between the two non-invasive tests. When a biometric method for determination of cut-off values between positive and negative UBT results with the smallest possible arbitrariness was used, the calculated statistical probability of a false diagnosis was lowest in the 10-min breath sample (0.20%), and 100% sensitivity and specificity was achieved. Our capsule method was also compared with the urea drink method and was found more reliable because no overlapping in ¹⁴CO₂ activity occurred between H. pylori-positive and -negative subjects, whereas conventional breath testing showed overlapping during the whole 30-min test period. Our study also showed that a fatty test meal lowers the ¹⁴CO₂ excretion the first 20 min and may adversely affect the accuracy of a rapid UBT. Conclusions: Supplying the ¹⁴C-urea in a capsule obviates the problem of false-positive results in early breath samples and makes it possible to diagnose H. pylori infection with 99.8% reliability from a single 10-min breath sample, without the use of a test meal or adjustments for assumed individual CO₂ production.     

Detection of Helicobacter pylori in Gastric Aspirates Using a Monoclonal Antibody-Based Test

Background/Aims

The objective of this study was to evaluate a monoclonal antibody-based test to detect Helicobacter pylori-specific antigen in gastric aspirates from humans.

Methods

Sixty-one volunteers were enrolled in the study. All of the subjects underwent a ¹³C-urea breath test (UBT) before esophagogastroduodenoscopy. Gastric aspirates were analyzed for pH and ammonia and used for polymerase chain reaction (PCR), culture, and monoclonal antibody-based detection of H. pylori. Multiple biopsies of the gastric antrum and body were obtained for a rapid urease test (RUT) and histological evaluation.

Results

Thirty-six subjects were H. pylori-positive and 25 were H. pylori-negative according to the UBT results. Compared with the H. pylori-negative subjects, H. pylori-positive subjects had a higher pH (4.77±1.77 vs 3.49±1.30, p<0.05) and ammonia level (1,130.9±767.4 vs 184.2±126.3, p<0.0001). The sensitivities and specificities of the PCR test, RUT, culture test, and monoclonal antibody-based test were 100% and 72%, 89% and 100%, 47% and 100%, and 78% and 100%, respectively.

Conclusions

The monoclonal antibody-based test for diagnosing H. pylori infection in gastric aspirates has increased sensitivity compared with the culture test and specificity as high as that of the RUT. The test may be useful as an additive test for examining gastric aspirates.     

Helicobacter pylori in the Oral Cavity:

To test the hypothesis that Helicobacter pylori may be transmitted by the oral–oral route, we applied nested PCR and DNA sequencing to detect and analyze H. pylori DNA in the oral cavity of 20 adult patients undergoing endoscopy. Dental plaques of molars, premolars, and incisors and saliva were collected. Additional paraffin-embedded gastric biopsies were analyzed in four patients. Two sets of highly sensitive and specific primers, EHC-U/EHC-L and ET5-U/ET-5L directed to a 860-bp fragment of H. pylori DNA, were used in the nested PCR. Eight patients had an active infection in the stomach determined with the [¹³C]urea breath test and the other 12 were negative. Nested PCR showed that all 20 subjects (100%) were positive for H. pylori in the oral cavity. DNA sequencing demonstrated that all tested PCR products of the expected size from the oral samples have more than 97% identity with that from H. pylori type strain ATCC 43629. However, sequences differed in oral samples from different subjects as well as between different oral locations and gastric biopsies within the same individuals. In conclusion, the oral cavity may be a permanent reservoir for H. pylori and can harbor multiple H. pylori strains at the same time.     

[14C]urea breath test for diagnosis ofHelicobacter pylori

H. pylori is a potent urease producer, a characteristic that has been exploited in the development of the[¹⁴C]- and [¹³C]urea breath tests. The prevalence of H. pylori infection also is known to increase with advancing age; however, the individual patient's age has not routinely been considered when interpreting urea breath test results. The aim of this study was to validate a short, age-adjusted [¹⁴C] urea breath test for use in diagnosing H. pylori infections. Forty-one subjects (28 volunteers, 13 patients) underwent esophagogastroduodenoscopy with biopsies. Subjects were defined as being H. pylori positive if histology or culture was positive. In addition, all subjects completed a 120-min [¹⁴C]urea breath test. A logistic regression analysis adjusting for age was used to estimate the probability of H. pylori positivity as a function of the¹⁴C values generated. Sixteen subjects were H. pylori-positive, and 25 were H. pylori negative. The¹⁴C values generated between 15 and 80 min were found to be equally predictive in identifying H. pylori-positive subjects. Advancing age was associated with a higher probability of H. pylori positivity. By taking advantage of the statistical probabilities, older patients could be accurately diagnosed with H. pylori at lower¹⁴C values. We found that [¹⁴C]urea breath test to be both a sensitive and specific test that can be abbreviated to a 30-min examination (total test time). Moreover, our mathematical model indicates that a patient's age should be considered in order to optimize interpretation of the [¹⁴C]urea breath test, although further observations are needed to confirm this model.Supported in part by grant DK34988 from the National Institutes of Health, U.S. Public Health Service.This work was presented in part at the American College of Gastroenterology Annual Meeting, New Orleans, October 1989, and published as an abstract in theAmerican Journal of Gastroenterology (84:1166, 1989).     

Gastric mucosa-associated lymphoid tissue lymphoma and Helicobacter pylori: Scratch and win

Gastric mucosa-associated lymphoid tissue (MALT) lymphoma is generally associated with Helicobacter pylori infection and, in the great majority of patients, regresses after eradication. H. pylori-negative MALT lymphoma occurs in a small minority of cases in which treatment is based on surgery or chemoradiotherapy. In the search for H. pylori based on histology and the C¹³ urea breath test, this report describes a case with a series of false-negative results, thus confirming the possibility of a lower detectability of H. pylori in patients with MALT gastric lymphoma and supporting the use of additional tests in evaluating such pathology, including polymerase chain reaction. Additionally, treatment with CD20 monoclonal antibody (rituximab) is suggested as an alternative to surgery or treatment with chemotherapy or radiotherapy in patients with truly H. pylori-negative gastric MALT lymphoma.     

Determination of the optimal cut-off value for the [13C]-urea breath test based on a Helicobacter pylori-specific polymerase chain reaction assay

BACKGROUND: This study was conducted to determine the optimal cut-off value and breath sample collection time for the [13C]-urea breath test based on the assessment of Helicobacter pylori status with a gastric juice-based polymerase chain reaction (PCR) assay. METHODS AND RESULTS: A total of 104 patients took 100 mg [13C]-urea orally and breath samples were collected at 5, 10, 20, 30 and 60 min. The increment of 13CO2:12CO, ratio from the baseline (delta13C) was measured using a laser spectroanalyser. The PCR assay was positive in 63 and negative in 41 patients. The optimal cut-off value of delta13C was calculated for each sample collection time so that the distance from the geometric mean value among Helicobacter pylori-positive patients and that from the arithmetic mean value among negative patients were simultaneously maximized. The cut-off value of 2.7% at 20 min had the longest distance, being separated by 3.16 SD from the two mean values. Using this cut-off value, the urea breath test showed 100% specificity and 98% sensitivity for the diagnosis of Helicobacter pylori infection.     

Studies of 13C-urea breath test for diagnosis of Helicobacter pylori infection in Japan

In recent years Helicobacter pylori infection has been implicated in the etiology of a variety of upper gastrointestinal diseases. The aim of this multi-center trial was to search for the cut-off value of the simple ¹³C-urea breath test (¹³C-UBT) for diagnosis of H. pylori infection, and to examine the sensitivity and specificity of ¹³C-UBT for culture, the rapid urease test (CLO test), histology, and serological tests. Two hundred and forty-eight patients participated in this study after giving their informed consent. Endoscopic biopsy specimens were taken from gastric antrum and corpus for culture (190 patients), CLO test (222 patients), and histology (98 patients). A serological test was carried out for all patients. H. pylori infection was established when culture was positive or more than two of the tests, histology, CLO test, and serological test, were positive, and non-infection status was established when the all tests more than two tests were negative. After baseline breath samples were taken, the patients (who had fasted) were given 100 mg of ¹³C-urea in 100 ml water while sitting; they washed out the mouth with water. They were then placed in the left lateral decubitus position for 5 min, and additional breath samples were taken 10, 20, 30, 45, and 60 min after urea administration, with patients in the sitting position. One hundred and sixty-five of the 248 patients were infected, 48 were not infected, and H. pylori infection status was not evaluated in 35 by endoscopic and serological tests. Breath samples at 20 min were employed to determine the cut-off value. Using the receiver operating characteristic (ROC) curve, we determined the cut-off value for a positive UBT at 2.5 Δ‰. The sensitivities of UBT for culture, CLO test, histology, and serological test were 98.4%, 98.6%, 100.0%, and 92.5%, and the specificities were 78.8%, 82.5%, 83.3%, and 87.3%, respectively. The cut-off value of 13C-UBT for the diagnosis of H. pylori infection was 2.5 Δ‰; this test is a simple and non-invasive method for the diagnosis of this infection and has high sensitivity and specificity. Received Nov. 18, 1996; accepted June 20, 1997     

Noninvasive detection ofHelicobacter pylori colonization in stomach using [11C]urea

Summary Helicobacter pylori is associated with chronic type B gastritis. Diagnosis can be made on gastric biopsy specimens and noninvasively using [¹³C]-or [¹⁴C]urea breath tests. Both breath tests require meticulous breath collection, and false positive results are possible from urease producing oral-pharyngeal flora. We used [¹¹C]urea, a positronemitting radionuclide allowing dynamic imaging, to measure metabolism of urea in the stomach of biopsy documentedH. pylori-positive patients. [¹¹C]urea was synthesized from¹¹CO₂ produced using a Van de Graaff accelerator and administered with [^99mTc]DTPA to control for loss of radioactivity via gastric emptying. Images were obtained externally by gamma camera every minute and¹¹CO₂ was monitored in the breath continuously for 30 min. AnH. pylori-positive patient exhibited a^99mTc/¹¹C activity ratio of 2.1 in the stomach 10–20 min following administration, compared to a 11 ratio in a negative control, indicating metabolism of urea to¹¹CO₂ with subsequent diffusion of¹¹C activity out of the stomach. The¹¹C activity in the breath peaked at 10–20 min in theH. pylori-positive patients. The short half-life of carbon-11 (20.4 min) alleviates radiation safety concerns and results in low absorbed radiation doses to patients.This work was supported in part by the National Science Foundation (grant R11-8110671), the Commonwealth of Kentucky through the Kentucky EPSCoR program, a grant from the University of Kentucky Association for Medical Research, and the Veterans Administration.