Comparison of stool immunoassay with standard methods for detecting Helicobacter pylori infection

Cost-effectiveness of six strategies for Helicobacter pylori diagnosis and management in uninvestigated dyspepsia assuming a high resource intensity practice pattern

BACKGROUND

Initial assessment of dyspepsia often includes noninvasive testing for Helicobacter pylori infection. Commercially available tests vary widely in cost and accuracy. Although there is extensive literature on the cost-effectiveness of H. pylori treatment, there is little information comparing the cost-effectiveness of various currently used, noninvasive testing strategies.

METHODS

A Markov simulation was used to calculate cost per symptom-free year and cost per correct diagnosis. Uncertainty in outcomes was estimated using probabilistic sensitivity analysis.

RESULTS

Under the baseline assumptions, cost per symptom-free year was $122 for empiric proton pump inhibitor (PPI) trial, and costs for the noninvasive test strategies ranged from $123 (stool antigen) to $129 (IgG/IgA combined serology). Confidence intervals had significant overlap.

CONCLUSIONS

Under our assumptions for how testing for H. pylori infection is employed in United States medical practice, the available noninvasive tests all have similar cost-effectiveness between one another as well as with empiric PPI trial.

Evaluation of a urine-based enzyme-linked immunosorbent assay test for the detection of Helicobacter pylori infection among 3- to 5-year-old Israeli Arab healthy children

We conducted a community-based study among 159 healthy Israeli Arab children aged 3 to 5 years old to examine the validity of the HpELISA kit (URINELISA, Otuska Phamaceuticals Co, Ltd, Tokyo, Japan) for detection Helicobacter pylori IgG antibodies in urine. The polyclonal H. pylori stool antigen test (Premier HpSA) served as the gold standard. The sensitivity, specificity, positive and negative predictive values of the URINELISA kit were 34.2%, 96.3%, 90% and 60%, respectively. Using a cutoff value calculated based on the receiver operating characteristic curve (0.066), the corresponding figures were 65.8%, 87.5%, 83% and 72%, respectively. These data indicate that the usefulness of the URINELISA test in epidemiological studies in healthy young children is limited.

Evaluation of the stool antigen test for Helicobacter pylori in children and adolescents

The stool antigen test for Helicobacter pylori is a noninvasive immunoassay to diagnose active infection with Helicobacter pylori in human fecal samples. Its performance in children and teenagers has been tested in some developed countries, showing a sensitivity and specificity above 90%, however, its accuracy in developing countries and in children under 6 years is not well established. To determine the accuracy of the test for diagnosing Helicobacter pylori infection in children and teenagers, we evaluated 133 patients (4 months to 17 years old). The gold standard was a positive culture or positive histology and rapid urease test. The test was done according to the manufacturer's instructions. However, modifications were introduced for better reproducibility. Samples were analyzed twice and results are expressed as optical density (OD) determined spectrophotometrically at 450 nm. HpSA was considered positive at OD > or =0.160 and negative at OD <0.140. One hundred twenty-seven of the 133 (95.5%) patients were included. There were no infected infants. The test showed a 94.6% sensitivity (95% CI: 90.6-98.5) and a 96.5% specificity (95% CI: 93.3-99.7). At ages 2 to 6 years the specificity was 96.4% (95% CI: 85.1-99.2) and the sensitivity was 80.0% (95% CI: 64.8-89.7), at ages 6 to 10 years the sensitivity was 100.0% and the specificity 95.7%, and above 10 years the sensitivity and specificity were 100.0%. We conclude that the test is efficient in adolescents and children, however there is a need for further studies with a greater number of patients for evaluation of its accuracy in infants.

Stool antigen test for the diagnosis of Helicobacter pylori infection: a systematic review

Our aim was to review systematically the diagnostic accuracy of the Helicobacter pylori stool antigen test. Bibliographical searches were performed in several electronic databases and abstracts from congresses up to May 2003. Eighty-nine studies (10,858 patients) evaluated the stool antigen test in untreated patients. Mean sensitivity, specificity, positive predictive value and negative predictive value were 91%, 93%, 92% and 87%, respectively. Analysis of the eight studies (1399 patients) in which pretreatment evaluation of the monoclonal stool antigen test was performed showed better (p < .001) results (96%, 97%, 96% and 97%, respectively), with a clearer distinction between positive and negative results. Thirty-nine studies (3147 patients) evaluated the stool antigen test for the confirmation of H. pylori eradication 4-8 weeks after therapy, with accuracies of 86%, 92%, 76% and 93% for mean sensitivity, specificity, positive predictive value and negative predictive value, respectively. Results were similar when a gold standard based on at least two methods was used. Relatively low accuracy was reported in some posttreatment studies with the polyclonal stool antigen test. However, excellent results (p < .001) were achieved in all the six studies evaluating the monoclonal stool antigen test 4-8 weeks posttreatment. Results evaluating the stool antigen test < 4 weeks posttreatment are contradictory. Proton-pump inhibitors seem to affect the accuracy of the stool antigen test. Sensitivity and/or specificity in patients with gastrointestinal bleeding may be suboptimal. The stool antigen test performs well in children. Finally, the stool antigen test seems to be a cost-effective method.

Review article: clinic-based testing for Helicobacter pylori infection by enzyme immunoassay of faeces, urine and saliva

Enzyme immunoassays have been used to detect Helicobacter pylori infection in human body materials such as faeces, urine and saliva. The stool antigen assay (HpSA), which uses polyclonal anti-H. pylori antibody as a capture reagent, has been widely used in the pre-treatment diagnosis of the infection in adults and children. Although the assay has the potential for monitoring eradication therapy, there are controversies over its use, especially at an early stage after treatment. The efficacy of the stool antigen assay can be modified by using monoclonal antibodies towards well characterized H. pylori faecal antigens. Two types of enzyme immunoassays (enzyme-linked immunosorbent assay [ELISA] and immunochromatography) have been used to detect antibodies to H. pylori in urine. Immunochromatography of urine is a rapid assay well suited for epidemiological studies. The salivary ELISA, used in a number of studies, has shown inconsistent results with less than optimum sensitivity and specificity. Urinary and salivary immunoassays may not distinguish between past and present infections, thus limiting their potential to monitor eradication therapy.

Evaluation of two stool antigen tests for the detection of Helicobacter pylori infection in the Chinese population

BACKGROUND AND AIM

The stool antigen test, the HpSA test, has been validated mainly in Western countries, but not properly in the Chinese population. Recently, another stool antigen test, the Apollo test, was developed, but its accuracy has rarely been validated. The aim of this study is to compare the accuracy of these two tests in the diagnosis of Helicobacter pylori infection in the Chinese population.

METHODS

Consecutive dyspeptic patients referred for upper endoscopy were recruited. During endoscopy, biopsies were taken for the rapid urease test and histological examination as the gold standard. Stool specimens were collected and used for the HpSA and Apollo tests.

RESULTS

Overall, 86 patients (39 males and 47 females, with a mean age of 55.8 years) were recruited. Helicobacter pylori infection was present in 44 (51%) patients as determined by the gold standard. The sensitivity, specificity and accuracy were 86.4, 100, and 93.0%, respectively, for the HpSA, and 90.9, 97.6, and 94.2%, respectively, for the Apollo test when cases with equivocal results were considered as positive. In addition, agreement was achieved in 81 (94.2%) cases between the two tests, with a Kappa value of 0.887.

CONCLUSION

Both the HpSA and Apollo tests achieve acceptable sensitivity and excellent specificity, with accuracies of over 90% for the detection of H. pylori infection in the Chinese population.

Different effects of short-term omeprazole, lansoprazole or pantoprazole on the accuracy of the (13)C-urea breath test

BACKGROUND

Proton pump inhibitors may interfere with the accuracy of the (13)C-urea breath test, but little information is available on the effect of standard doses of various proton pump inhibitors on this test.

AIM

To evaluate the effect of short-term standard doses of omeprazole, lansoprazole and pantoprazole on the accuracy of the standardized (13)C-urea breath test.

METHODS

A total of 124 patients with Helicobacter pylori infection, diagnosed on the basis of gastric histology, rapid urease test and (13)C-urea breath test, were studied. These patients received omeprazole, 20 mg/day, lansoprazole, 30 mg/day, or pantoprazole, 40 mg/day, for 2 weeks according to a randomized protocol. (13)C-Urea breath test was repeated on days 4, 7 and 14 while on therapy and 7 days after proton pump inhibitor withdrawal.

RESULTS

Of the patients receiving omeprazole and lansoprazole, 30% (12/40) and 20% (8/41), respectively, became (13)C-urea breath test negative during therapy, compared with none of the 42 patients treated with pantoprazole (P < 0.05). All the false negative (13)C-urea breath test results returned to positive within 1 week of drug withdrawal, with a mean recovery to 84.7 +/- 15.6% of baseline delta(13)CO(2).

CONCLUSIONS

Short-term omeprazole and lansoprazole interfere with the 13C-urea breath test, although a return to positive test results invariably occurs within 1 week of proton pump inhibitor withdrawal. In contrast, the accuracy of the (13)C-urea breath test does not appear to be significantly impaired by short-term pantoprazole, which therefore may not necessarily be withdrawn before this test.

Detection of Helicobacter pylori antigen in faeces by enzyme immunoassay

The detection of Helicobacter pylori antigen directly in faecal specimens may offer an alternative non-invasive method for determining the presence of H. pylori infection. This study compared the performance of the Premier Platinum HpSA enzyme immunoassay (HpSA) with histology and CLOtest, a rapid urease test. Of 134 patients undergoing upper gastrointestinal endoscopy, 37 (28%) were H. pylori-positive by histology and CLOtest. Using the HpSA test, H. pylori was detected in 35 H. pylori-positive patients (95% sensitivity) and one H. pylori-negative patient (99% specificity). The positive and negative predictive values for HpSA were 97 and 98%, respectively. HpSA is a rapid, easily performed, non-invasive method for detecting H. pylori.

Recrudescence and reinfection with Helicobacter pylori after eradication therapy in Bangladeshi adults

BACKGROUND & AIMS

In developing countries where Helicobacter pylori infection is widespread, posttherapeutic recurrence rates may be high. Many of the limited studies available have methodological problems and show varied recurrence rates. We determined late recrudescence rates, true reinfection, and ulcer recurrence.

METHODS

One hundred five Bangladeshi patients with H. pylori infection and duodenal ulcer disease were treated with a triple therapy. Follow-up included 13C-urea breath tests, endoscopy, and biopsy-based tests. In reinfected patients, genomic typing compared pretherapeutic and posttherapeutic strains.

RESULTS

Recrudescence, associated with nitroimidazole-based treatment, occurred in 15 of 105 patients (14%) within the first 3 months, but only 8 of 105 patients tested positive 4 weeks after therapy ended. True reinfection was diagnosed in 11 of 105 patients between 3 and 18 months after therapy. The annual reinfection rate was 13%, based on a total follow-up of 84.7 patient years. Ulcer relapse occurred in 2 of 15 (13%) recrudescence cases and in 6 of 11 (55%) reinfection cases, but also in 4 of 73 (5%) H. pylori-negative patients.

CONCLUSIONS

In Bangladesh, late recrudescence of H. pylori after eradication therapy occurs within the first 3 months. The reinfection rate is high and might influence cost-benefit analyses for determining diagnostic and therapeutic procedures.

Diagnosis of Helicobacter pylori infection by stool antigen determination: a systematic review

Recently a new, noninvasive diagnostic test based on the detection of Helicobacter pylori stool antigen (SA) has been developed. The aim of this study was to systematically review the experience on H. pylori SA test for the diagnosis of H. pylori infection. Bibliographic searches were performed in the PubMed database and abstracts from several congresses. A total of 43 studies fulfilled the inclusion criteria and evaluated H. pylori SA test accuracy for the diagnosis of H. pylori infection in nontreated patients. Overall, 4769 patients were included. The sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) (weighted mean) were, respectively: 92.4% (95% CI = 91-93%), 91.9% (91-92%), 92.1% (91-93%), and 90.5% (90-91%). Therefore the SA test can definitively be considered an accurate noninvasive method for the diagnosis of H. pylori infection in untreated patients. A total of 25 studies including 2078 patients evaluated H. pylori SA test for the confirmation of H. pylori eradication > or = 4 wk after completion of therapy. Sensitivity, specificity, PPV and NPV (weighted mean) were: 88.3% (87-90%), 92% (91-93%), 75.1% (73-77%), and 94.8% (94-96%). Although most studies showed that SA test is an accurate method to confirm H. pylori eradication > or = 4 wk after treatment, these favorable results were not confirmed in other studies. Further investigation is necessary to explain these discrepancies, as well as to clarify the precise time for confirmation of eradication after therapy, the appropriate cutoff point for the SA test, and which factors influence it. Proton pump inhibitors seem to affect the accuracy of SA test, but the negative effect disappears 1-2 wk after stopping treatment. The SA test is technically feasible in patients with upper GI bleeding. although the true diagnostic accuracy in this group of patients remains to be more fully assessed. Finally, the SA test seems to be a highly cost-effective method for the diagnosis of H. pylori infection.

A prospective study of a one-week nonbismuth quadruple therapy for childhood Helicobacter pylori infection

PURPOSE

In the eradication of Helicobacter pylori infection, a 1-week therapy improves patient compliance, but drug resistance may limit its efficacy. The effectiveness of the 1-week nonbismuth quadruple therapy was studied prospectively in children with proven H pylori infection in a population with a high rate of metronidazole resistance.

METHODS

All pediatric patients who presented to our institutions with acute and chronic upper gastrointestinal conditions requiring endoscopy from June 1997 to February 2000 were investigated prospectively for H pylori infection. Gastric biopsy specimens were analyzed with rapid urease test and histopathology, H pylori-positive children were treated with omeprazole, clarithromycin, amoxicillin, and metronidazole for 7 days. The result of treatment was assessed 1 month after treatment with endoscopy and biopsy. The same treatment was repeated for 2 weeks if H pylori was still present. In patients who needed a third endoscopy, their biopsy specimens were cultured to determine antibiotic sensitivity. Results were correlated with patients' symptoms and endoscopic findings.

RESULTS

Thirty-three children with acute (severe epigastric pain, n = 14; gastrointestinal bleeding, n = 9) and chronic (recurrent abdominal pain, n = 7; anemia, n = 3) conditions were treated for H pylori. Thirty-one (94%) were confirmed to have H pylori eradicated by a 1-week therapy, whereas 1 patient had eradication after a further 2-we'ek therapy (3.3%). The only unresponsive patient had H pylori resistant to both clarithromycin and metronidazole. All ulcers and erosions healed after the eradication of H pylori. Three patients had persistent recurrent abdominal pain despite H pylori eradication.

CONCLUSIONS

The 1-week therapy with omeprazole, clarithromycin, amoxicillin, and metronidazole is an effective treatment of H pylori in children in a population with a high incidence of metronidazole resistant strain of H pylori. Peptic ulcers and erosions healed with the eradication of the bacteria.

Validity of a Helicobacter pylori stool antigen assay for the assessment of H. pylori status following eradication therapy

BACKGROUND

A Helicobacter pylori stool antigen (HpSA) test has been proposed as a valid alternative to the 13C-urea breath test (13C-UBT) for the non-invasive detection of H. pylori infection in primary diagnosis. Published reports show conflicting results with regard to the test's diagnostic accuracy after eradication therapy. The aim of the present study was to assess the diagnostic value of the HpSA test and to determine the optimal discriminating cut-off value in patients following H. pylori eradication therapy.

METHOD

Stool samples were collected and the 13C-UBT was performed in 113 patients 4-6 weeks after eradication therapy. A validated test protocol for the 13C-UBT was used. Stool specimens were analysed with the Premier Platinum HpSA enzyme immunoassay (EIA). A receiver operator characteristics (ROC) analysis was performed to define the optimal cut-off value on the basis of the results of the 13C-UBT.

RESULTS

The results of the 13C-UBT showed that H. pylori eradication was successful in 83/113 (73%) patients. According to the manufacturer, the cut-off value for the HpSA test is 0.14 optical density, but this does not appear to be valid after eradication therapy (sensitivity 76.7%, specificity 98.8%). On the basis of ROC analysis, the optimal cut-off value after therapy was determined to be 0.11 optical density, giving a sensitivity of 93.3% and a specificity of 93.9%.

CONCLUSION

The HpSA test is a valid test for the assessment of H. pylori status after eradication therapy, provided an adjusted cut-off value is applied.

[Helicobacter pylori infections: antigen detection in stool samples]

BACKGROUND

The aim of this study is to evaluate a new diagnostic test to detect Helicobacter pylori antigen in stool samples (HpSA), and compare the results with those obtained by standard techniques (rapid urease test,culture, histological examination of gastric biopsy specimens,13C-urea breath test and serology), in a paediatric population with gastrointestinal symptomatology.

PATIENTS AND METHODS

Sixty patients with dyspeptic symptoms (37 females and 23 males;mean age 10.9 years) attending the Gastroenterology Service were included in the study. Exclusion criterium was previous treatment with proton pump inhibitors, bismuth compounds or antibiotics. Rapid urease test, culture and histologic study of gastric biopsies,13C-urea breath test and serology, as well as HpSA, were performed to all patients.

RESULTS

Forty seven patients were considered infected by H.pylori on the basis of bacterium isolation and 13C-urea breath test positivity. HpSAwas detected in 45 of the 47 H.pylori positive patients(95.7%). There were no HpSA false positive.

CONCLUSION

Our results show that this new test is highly sensitive (95%) and specific(100%) for detection of H. pylori infection. It has some advantages over other non invasive techniques: it is easy to perform,requires no blood samples and its cost is lower than that of 13C-urea breath test.

Accuracy of the stool antigen test in the diagnosis of Helicobacter pylori infection before treatment and in patients on omeprazole therapy

AIM

To evaluate the Helicobacter pylori stool antigen (HpSA) test in the assessment of H. pylori infection and the effect of omeprazole treatment on its accuracy.

METHODS

Study 1: 140 dyspeptic patients were enrolled in the study and defined as H. pylori positive if histology and rapid urease test, or culture alone were positive. HpSA was performed on all patients and 13C-urea breath test (UBT) on 87. Study 2: 75 patients testing positive using both UBT and HpSA, were given omeprazole 20 mg for 2 weeks (Group A) or omeprazole 40 mg for 2 weeks (Group B), or OAC for 1 week (group C). A Helicobacter pylori stool antigen test was performed on all patients on days 3, 5, 7 and 14 during treatment, and also on days 7 and 14 post-treatment in groups A and B. UBT was performed in groups A and B on days 7 and 14 during treatment, and days 7 and 14 post-treatment.

RESULTS

80/140 patients were H. pylori positive. The sensitivity and specificity of HpSA were 93.8 and 90%, similar to UBT (93.9 and 92.1%). Omeprazole significantly reduced both HpSA and UBT values, resulting in a decreased accuracy. Of 25 patients receiving 20 mg omeprazole, HpSA gave 5 and 6 false negatives after 7 and 14 days treatment respectively, while UBT gave 4 and 7 false negatives after 7 and 14 days treatment. Of 25 patients receiving 40 mg omeprazole, HpSA gave 7 and 9 false negatives after 7 and 14 days of treatment, while UBT gave 8 and 9 false negatives after 7 and 14 days of treatment. Two weeks after stopping omeprazole treatment, the HpSA and UBT were positive in all cases.

CONCLUSIONS

The Helicobacter pylori stool antigen test is valuable in the assessment of H. pylori infection. Short-term omeprazole treatment decreases the accuracy of both HpSA and UBT in a similar manner.

Review article:invasive and non-invasive tests for Helicobacter pylori infection

There are two general ways in which a diagnosis of infection by Helicobacter pylori can be made: by using either an invasive or non-invasive procedure. The invasive procedures involve an endoscopy and biopsy. A biopsy is essential because often the mucosa may appear macroscopically normal but nevertheless be inflamed. A biopsy is obtained by histological examination, culture, polymerase chain reaction or detection of the presence of urease activity in biopsy material. The non-invasive tests that can be used to diagnose the infection are serology, detection of labelled metabolic products of urea hydrolysis in the breath (13CO2, 14CO2), the urine or the blood, and detection of H, pylori antigen in a stool specimen. At present no single test can be relied upon to detect definitely colonization by H. pylori, and a combination of two is recommended if this is feasible. The choice of the test to be used is not straightforward and may vary according to the clinical condition and local expertise.

Comparison of an enzyme immunoassay for the detection of Helicobacter pylori antigens in the faeces with the urea breath test

BACKGROUND

Current diagnostic tests for Helicobacter pylori are invasive (endoscopy) or indirect (urea breath test, serology).

AIMS

To evaluate a new enzyme immunoassay (EIA) which detects H pylori antigens in faeces, by comparing its sensitivity and specificity in children with the (13)C urea breath test (UBT).

METHODS

A total of 119 children underwent a UBT and provided a faecal sample for antigen testing within seven days. After an overnight fast each child provided a pretest breath sample, and samples at 30 and 40 minutes after ingestion of 100 mg (13)C labelled urea. (13)C enrichment of breath was measured by isotope ratio mass spectrometry. Faeces were stored at -70 degrees C until antigen testing, using the EIA. Samples were read spectrophotometrically at 450 nm and results were interpreted using recommended cut offs of optical density <0.14 as negative, >/=0.16 as positive, with >/=0.14 and <0. 16 representing equivocal results. Sensitivity and specificity were calculated using the manufacturer's cut off compared with UBT.

RESULTS

Sensitivity and specificity were 88% and 82%, respectively. Negative and positive predictive values were 97% and 58%.

CONCLUSIONS

The EIA is an alternative, non-invasive, and easy to use method for the detection of H pylori in children. Its high negative predictive value suggests a role in screening out uninfected children.

The cost-effectiveness of diagnostic testing strategies for Helicobacter pylori

OBJECTIVE

Several noninvasive methods are now available for diagnosing Helicobacter pylori infection. Because the prevalence of H. pylori infection is variable in patients requiring testing, the optimal testing strategies may vary under different conditions. The aim of this study was to evaluate the cost-effectiveness of competing diagnostic strategies for H. pylori in patients with varying H. pylori prevalence.

METHODS

A decision analysis was performed comparing the costs per number of correct diagnoses achieved by alternative sequential testing strategies. Estimates of H. pylori prevalence and test characteristics were derived from a systematic review of the MEDLINE bibliographic database. Cost estimates were derived from the 2000 Medicare Fee Schedule.

RESULTS

The enzyme-linked immunosorbent assay (ELISA) test had the lowest cost per correct diagnosis at low (30%), intermediate (60%), and high (90%) prevalence ($90-$95/correct diagnosis), but its diagnostic accuracy was low (80-84%). At low and intermediate prevalence the stool test was more accurate (93%), with an average cost of $126-$127 per correct diagnosis. Additional confirmatory testing of positive or negative tests increased the diagnostic accuracy of the stool test, but had high incremental costs. ELISA testing was preferable when prevalence rates were very high (90%), and using a confirmatory urea breath test for negative ELISA tests increased the diagnostic accuracy to 96%, with modest incremental costs. If the cost of the breath test was <$50 or if the cost of the stool test is >$82, breath testing became preferable to stool testing. If the cost of the stool test fell to <$20, it became preferable to ELISA. Similarly, if the cost of the ELISA serology was >$39 then stool testing became preferable at all prevalence rates. Fingerstick whole blood tests were not cost-effective.

CONCLUSIONS

The choice of an initial test for H. pylori detection depends on the prevalence of H. pylori infection and the value placed on increased diagnostic accuracy. Although ELISA results in the lowest cost-effectiveness ratios, in patients at low-intermediate pretest probability of infection, the stool test provides increased accuracy, with modest incremental costs.