| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
|
|
|
|||||||
|
|||||||||
1,2,3,4Departments of Gastroenterology1, Microbiology and Clinical Microbiology2, Pathology3 and Biostatistics4, Istanbul University, Cerrahpasa Faculty of Medicine, 34303 Kocamustafapasa, Istanbul, Turkey
Correspondence B. Kocazeybek bekirkcz{at}superonline.com
Received October 1, 2004
Accepted June 13, 2005
The aim of the current study was to assess the reliability of two enzyme immunoassays in detecting the Helicobacter pylori status of stool specimens of Turkish dyspeptic patients in the post-treatment period. Forty-eight patients with non-ulcer dyspepsia who were positive for H. pylori underwent a 1 week regimen of triple therapy. Stool samples of patients were obtained 2 and 6 weeks after eradication therapy and a [13C]urea breath test was performed 6 weeks after therapy in order to assess the reliability of mAb-based (Amplified IDEIA HpStAR, DakoCytomation) and polyclonal-antiserum-based (Premier Platinum HpSA, Meridian Diagnostics) stool antigen test kits and to compare their diagnostic accuracies. Using a minimum cutoff OD450 value of 0.19 for Amplified IDEIA HpStAR and 0.16 for Premier Platinum HpSA the sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy of the tests were determined 2 and 6 weeks after completion of eradication therapy. At both the second and the sixth week in the post-treatment period the diagnostic accuracy of Amplified IDEIA HpStAR was significantly better than the Premier Platinum's (75 % versus 50 %, S2 = 6.4; P = 0.011, and 90 % versus 69 %, S2 = 6.316; P = 0.012, respectively). In light of these findings the mAb-based Amplified IDEIA HpStAR has a high diagnostic accuracy for H. pylori infection in Turkish dyspeptic patients 6 weeks after completion of eradication therapy.
 |
INTRODUCTION |
|---|
 TOP INTRODUCTION METHODSRESULTS AND DISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
In primary care a test-and-treat approach is recommended for patients under the age of 45 years with persistent dyspepsia, except those who have predominantly gastro-oesophageal reflux disease symptoms or alarm symptoms such as unexplained weight loss, dysphagia, recurrent vomiting, digestive bleeding or anaemia (Malfertheiner et al., 2002). These authors recommend the diagnosis of infection and monitoring of eradication by urea breath test (UBT) or stool antigen tests if endoscopy is clinically not indicated. Testing after the eradication treatment should be performed in all patients after a minimum of 4 weeks. UBT is a very sensitive and specific method with very high diagnostic accuracy but has a number of disadvantages including the high cost, and the need for trained personnel and specialized instrumentation to obtain and to interpret the breath samples.
As Turkey is a developing country and the prevalance of H. pylori infection is as high as 85 % (Us & Hascelik, 1998; Selimoglu et al., 2002), local validation of inexpensive, non-invasive tests in the post-treatment check-up period is an important issue. Thus the aim of the present study was to compare the diagnostic accuracy of two enzyme immunoassays (EIAs), namely Amplified IDEIA HpStAR (formerly the FemtoLab H. pylori kit) and Premier Platinum HpSA, for detecting H. pylori antigens in Turkish dyspeptic patients’ stool specimens after eradication therapy.
|
METHODS |
|---|
|
TOPINTRODUCTIONMETHODSRESULTS AND DISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
A patient was classified as being H. pylori positive if the culture and/or both histology and rapid urease test were positive, and as H. pylori negative only if all of these tests were negative. Eleven patients with discordant results were excluded and 58 of the remaining 78 patients (75 %) who were H. pylori positive were enrolled in the study and received an eradication treatment consisting of lansoprazole 30 mg b.i.d., clarithromycin 500 mg b.i.d. and amoxycillin 1000 mg b.i.d. for 1 week. Forty-eight of 58 patients (83 %) were available for follow-up for 6 weeks in the post-treatment period and completed the entire course of the trial.
The study group only consisted of patients with non-ulcer dyspepsia who were not treated with antibiotics, bismuth-containing compounds, histamine-2 receptor antagonists or proton pump inhibitors during follow-up. Patients were asked to return their stool samples 2 and 6 weeks after the end of eradication therapy. The stool samples were divided into aliquots, frozen (–80 °C) and stored until tested. Stool specimens were analysed for H. pylori antigen using the Amplified IDEIA HpStAR (DakoCytomation) and the Premier Platinum HpSA (Meridian Diagnostics) EIAs as described by the manufacturers. The results were analysed by spectrophotometry (EL 312e, Biotek). OD450 values of greater than 0.19 for the Amplified IDEIA HpStAR kit and 0.16 for the Premier Platinum kit were recorded as positive.
In all patients, monitoring of eradication was performed by [13C]UBT (Helicobacter Test INFAI) for comparison using a validated protocol (Cadranel et al., 1998) 6 weeks after the therapy was discontinued. The test was performed after an overnight fast of 12 h. Breath samples were collected in duplicate before and 30 min after ingestion of 200 ml of orange juice and 75 mg of [13C]urea dissolved in 30 ml of tap water. Breath samples were analysed by isotope-ratio mass spectrometry (GV 2003) and results were expressed as ‘delta over baseline’ (DOB). DOB >4 
was considered positive.
The study was approved by the local ethics committee of our faculty and all patients gave their written informed consent to participate in the study.
Standard methods were used to calculate sensitivity, specificity, predictive values of positive and negative results, and 95 % confidence intervals of these values. The S2 and Fisher's exact tests were used to compare sensitivities and specificities, and P < 0.05 was regarded as identifying a significance. Calculations were performed using conventional software (SPSS 12 for Windows).
|
RESULTS AND DISCUSSION |
|---|
|
TOPINTRODUCTIONMETHODSRESULTS AND DISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
Using a minimum OD450 cutoff value of 0.19 for the Amplified IDEIA HpStAR kit and 0.16 for the Premier Platinum HpSA kit the sensitivities, specificities, PPVs, NPVs and diagnostic accuracies of both tests were determined 2 weeks and 6 weeks after eradication therapy (Table 1). After 2 weeks of eradication therapy, the specificity and diagnostic accuracy of the mAb Amplified IDEIA HpStAR were significantly greater than those of the polyclonal Premier Platinum HpSA (S2 = 7.333, P = 0.007; S2 = 6.4, P = 0.011, respectively), but the sensitivities, PPVs and NPVs were not statistically different (P = 1, S2 = 2.095; P = 0.148, P = 0.539, respectively). At the sixth week in the post-treatment period the sensitivities, specificities, PPVs and NPVs of the tests were not significantly different (P = 0.169, S2 = 3.264; P = 0.071, S2 = 3.142; P = 0.076, P = 0.097, respectively), but the diagnostic accuracy of the Amplified IDEIA HpStAR was significantly superior to the Premier Platinum's (S2 = 6.316; P = 0.012). The comparisons of the overall diagnostic accuracies of Amplified IDEIA HpStAR at week 2 (36/48, 75 %) and week 6 (43/48, 90 %) (S2 = 3.503; P = 0.061), and of Premier Platinum at week 2 (24/48, 50 %) and week 6 (33/48, 69 %) (S2 = 3.498; P = 0.061) did not reach statistical significance.
|
The receiver operator characteristics (ROC) analyses of both tests at the second and sixth weeks are shown in Fig. 1(a) and Fig. 1(b), respectively.
|
Several invasive and non-invasive diagnostic methods have been proposed for detecting H. pylori since Marshall and Warren (1984) isolated a Campylobacter-like organism from the stomachs of patients with gastritis and peptic ulcer disease. One of the attractive novel concepts is based on the detection of H. pylori in faeces. Recently stool EIAs detecting H. pylori antigens have been introduced. This method has the advantage of being inexpensive, non-invasive and easy to perform. The first stool antigen test to be marketed was the Premier Platinum HpSA, which is based on reactivity of polyclonal antiserum. Subsequently the mAb-based Amplified IDEIA HpStAR kit became available.
Gisbert & Pajares (2004) carried out a meta-analysis of 39 studies (3147 patients) that evaluated different monoclonal and polyclonal stool antigen tests for the confirmation of H. pylori eradication 4–8 weeks after therapy. These authors reported overall accuracies for the monoclonal and polyclonal tests of 86 %, 92 %, 76 % and 93 % for mean sensitivity, specificity, PPV and NPV, respectively. In the same meta-analysis it was mentioned that relatively low accuracy was reported in some post-treatment studies with the polyclonal stool antigen test and, when compared to the polyclonal test, excellent results were achieved in all the six studies evaluating the mAb-based stool antigen tests at 4–8 weeks post-treatment (96 % and 97 % for mean sensitivity and specificity, respectively).
In the current study, 6 weeks after completion of the eradication treatment, the sensitivity and specificity of the mAb-based stool test were better than those of the polyclonal-based test. Despite our small study population (48 patients, 33 of them successfully eradicated thus only 15 H. pylori-positive patients) the overall diagnostic accuracy of the Amplified IDEIA HpStAR mAb-based kit at the sixth week was significantly greater than the Premier Platinum polyclonal-antibody-based kit (90 % versus 69 %, S2 = 6.316; P = 0.012). This is in keeping with the meta-analysis of Gisbert & Pajares (2004), Makristathis et al. (2000), Agha-Amiri et al. (2001) and Weingart et al. (2004), who all report high sensitivity and specificity of the mAb-based test kit before and after eradication.
Although the Premier Platinum polyclonal-antibody-based stool antigen test is a recommended alternative to the UBT for the primary diagnosis of H. pylori, its use in the post-treatment setting is only recommended when the UBT is not available (Malfertheiner et al., 2002) as there are conflicting reports of its efficacy. Several investigators (e.g. Trevisani et al., 1999; Forne et al., 2000; Bilardi et al., 2002) have expressed concern about the specificity of the test after therapy, whereas Vaira et al. (2000) and Odaka et al. (2002) considered the test useful. The differences in these studies may be attributable to antigenic variation within the samples tested (Makristathis et al., 2000).
The second aim of the present study was to investigate whether the use of stool EIAs was appropriate for the evaluation of eradication outcome as early as 2 weeks after the end of therapy, as a recent study (Odaka et al., 2002) concluded that the polyclonal HpSA test was useful for evaluating eradication success even 2 weeks after the completion of treatment. They found that the sensitivity of the test was 88.9 % versus 88.9 %, and the specificity was 90.9 % versus 97.1 %, 2 and 6 weeks after eradication therapy, respectively. Our results indicate that applying either the mAb- or polyclonal-based test 2 weeks post-therapy results in a high number of false-positive results and is therefore not an appropriate alternative to the recommended 6 week period (Table 1).
Stool antigen tests are inexpensive, simple and easy to perform, and do not require dedicated equipment; therefore local validation in developing countries is important. Although a major limitation of the present study is the small number of patients studied, in particular as only 15 patients failed eradication, the diagnostic accuracy of the mAb test was significantly better than the Premier Platinum polyclonal-antibody-based kit. We therefore propose that the mAb-based Amplified IDEIA HpStAR should be considered as a useful test for monitoring H. pylori status 6 weeks after completion of treatment in Turkish dyspeptic patients.
|
ACKNOWLEDGEMENTS |
|---|
|
TOPINTRODUCTIONMETHODSRESULTS AND DISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
|
REFERENCES |
|---|
|
TOPINTRODUCTIONMETHODSRESULTS AND DISCUSSIONACKNOWLEDGEMENTSREFERENCES |
|---|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| INT J SYST EVOL MICROBIOL | J MED MICROBIOL | MICROBIOLOGY | J GEN VIROL | ALL SGM JOURNALS |
