Comparison of Two Rapid Whole-Blood Tests for Helicobacter pylori Infection in Chinese Patients

Consecutive Chinese patients undergoing endoscopy for dyspepsia were tested for Helicobacter pylori infection by two rapid whole-blood tests: FlexPack HP (Abbott Laboratories) and Helisal One-Step (Cortecs Diagnostics). Biopsy-based tests (rapid urease test and histology) and the [¹³C]urea breath test were used as the “gold standard.” One hundred sixty-one consecutive patients were studied, and 88 (54.7%) were confirmed to have H. pylori infection. The sensitivities, specificities, and positive and negative predictive values were 81.8%, 83.6% (P = 0.008), 85.7% (P = 0.04), and 79.2% for FlexPack HP and 84.1%, 63.0% (P = 0.008), 73.3% (P = 0.047), and 76.7% for Helisal One-Step, respectively.     

Evaluation of Pyloriset Dry, a new rapid agglutination test for Helicobacter pylori antibody detection.

We evaluated the performance of a new latex agglutination test, Pyloriset Dry (Orion Diagnostica, Espoo, Finland), in the simultaneous detection of immunoglobulin G (IgG), IgA, and IgM antibodies to Helicobacter pylori and compared it with that of the Pyloristat test (BioWhittaker, Fontenay-sous-Bois, France), an enzyme-linked immunosorbent assay detecting IgG to H. pylori, for 96 untreated dyspeptic patients who had undergone gastroduodenal endoscopy. Infection was diagnosed in 56 cases by positive culture and/or positive Giemsa stain and rapid urease test (antral biopsies) and was associated with chronic gastritis in 52 patients. Forty noninfected patients did not have chronic gastritis. The sensitivity of Pyloriset Dry was 91.1%. The sensitivity of Pyloristat was 91.1 or 82.1%, depending on whether equivocal results were considered positive or negative, respectively. Both tests had a specificity of 87.5%. Their performances were not statistically different. Thus, Pyloriset Dry is an alternative to serological tests for adults, particularly when a small number of serum samples has to be tested.     

Objective Interpretation of the Rapid Urease Test for Helicobacter pylori Infection Using Colorimetry

BackgroundThe rapid urease test (RUT) is a major diagnostic tool for detecting Helicobacter pylori infection. This study aimed to establish an objective method for measuring the color changes in the RUT kit to improve the test’s diagnostic accuracy.MethodsA UV-visible spectrophotometer was selected as the colorimeter; experiments were conducted in three stages to objectively identify the color changes in the RUT kit.ResultsFirst, the urea broth solution showed an identifiable color change from yellow to red as the pH increased by 0.2. The largest transmittance difference detected using the UV-visible spectrophotometer was observed at a 590-nm wavelength. Second, the commercialized RUT kit also showed a gradual color change according to the pH change detected using the UV-visible spectrophotometer. Third, 13 cases of negative RUT results with a biopsy specimen and 16 of positive RUT results were collected. The transmittance detected using the UV-visible spectrophotometer showed a clear division between the positive and negative RUT groups; the largest difference was observed at a 559-nm wavelength. The lowest transmittance in the negative RUT group was 64, while the highest in the positive RUT group was 56, at the 559-nm wavelength. The UV-visible spectrophotometry reading showed a consistency of 92.7% compared with that of manual reading.ConclusionA transmittance of 60 at a 559-nm wavelength detected using UV-visible spectrophotometer can be used as a cutoff value for interpreting RUT results; this will help develop an automatic RUT kit reader with a high accuracy.     

Evaluation of a New Serologic Test for Diagnosis of Helicobacter pylori Infection in Children

 A new semiquantitative enzyme immunoassay (Platelia Helicobacter pylori; Sanofi Diagnostics Pasteur, France) was evaluated and compared with two other serological assays (Gap-test IgG; Bio-Rad, France; and Cobas Core; Roche, Switzerland) for the diagnosis of Helicobacter pylori infection in children. The three tests were compared with the examination of biopsy samples obtained from 160 dyspeptic subjects (mean age, 9±4.7 years). Discrepant results were studied using an immunoblot technique. The response obtained for the Platelia assay in children was significantly lower than that obtained in a previously described population of 92 adults (Helicobacter pylori-negative mean ratios, 0.376 vs. 0.504, P<0.000783;Helicobacter pylori-positive mean ratios, 1.95 vs. 2.67, P<0.000003). Thus, the optimal cut-off for children (0.80) was lower than the one recommended for adults (1.10). According to the Receiver Operating Characteristic (ROC) curve analysis and to the Wilcoxon value, the Platelia and Cobas Core assays showed the highest discriminatory properties (Wilcoxon value, 0.94 for both) compared with the Gap-test IgG (Wilcoxon value, 0.91). When the newly established cut-off value (0.80) was used, the performance of Platelia was equivalent to that of Cobas Core (sensitivity: 94.4% for each; respective specificities, 86.8% and 90.6%). The Gap-test IgG had a lower sensitivity (maximum, 79%) and a higher specificity (maximum, 95.3%), but there were difficulties in interpretation because its grey zone encompassed 12% of the sera. In conclusion, the results showed good performance of the Platelia Helicobacter pylori assay and confirmed the merit of a specific cut-off value for use of this test in children.     

Evaluation of Immunological Rapid Urease Testing for Detection of Helicobacter pylori

 The aim of this study was to evaluate in clinical specimens the immunological rapid urease test (IRUT), a new diagnostic system for detection of Helicobacter pylori which employs a monoclonal antibody against Helicobacter pylori urease. Helicobacter pylori urease adsorbed on a solid-phase tip coated with a monoclonal antibody against Helicobacter pylori urease after 15 min of incubation with a gastric mucus sample solution was measured by the pH change of the urea solution inside the tip. The detection limit of Helicobacter pylori urease using this system was determined and compared with that of a commercially available rapid urease test. Clinical evaluation of the system was performed in 155 patients. The IRUT could detect 0.25 milli-international units (mIU) of Helicobacter pylori urease per milliliter in less than 20 min. If a patient with at least one positive result in a standard test for Helicobacter pylori was considered to be Helicobacter pylori positive, the sensitivity, specificity, positive and negative predictive values of the system were calculated as 95.2%, 98.9%, 98.4% and 96.8%, respectively. However, 10 of 19 Helicobacter pylori-positive patients in whom the pH change was less than 0.1 had negative results in at least one of the standard tests, whereas the IRUT correctly detected Helicobacter pylori in all but 3 of these 19 patients. The IRUT accurately determined the Helicobacter pylori status of 75 (98.7%) of 76 patients who had completed treatment. This system has high sensitivity for the detection of Helicobacter pylori, especially in patients with low urease activity.     

Evaluation of a Rapid Immunochromatographic Test for Diagnosis of Dengue Virus Infection

A rapid (<7-min) immunochromatographic test for immunoglobulin M (IgM) and IgG antibodies to dengue viruses was evaluated by using hospital admission and discharge sera from 124 patients. The reference laboratory diagnosis was based on the results of virus isolation, hemagglutination-inhibition assay (HAI), and enzyme immunoassay (EIA). By the standard assays, patients experienced primary dengue virus infection (n = 30), secondary dengue virus infection (n = 48), Japanese encephalitis (JE) virus infection (n = 20), or no flavivirus infection (n = 26). The rapid test demonstrated 100% sensitivity in the diagnosis of dengue virus infection and was able to distinguish between primary and secondary dengue virus infections through the separate determinations of IgM and IgG. For all patients with primary dengue virus infection a positive test for IgM to dengue virus and a negative test for IgG to dengue virus were obtained, whereas for 46 of 48 patients (96%) with secondary dengue virus infection, a positive test for IgG to dengue virus with or without a positive test for IgM to dengue virus was obtained. The remaining two patients with secondary dengue virus infection had positive IgM test results and negative IgG test results. Furthermore, the rapid test was positive for patients confirmed to be infected with different dengue virus serotypes (12 infected with dengue virus serotype 1, 4 infected with dengue virus serotype 2, 3 infected with dengue virus serotype 3, and 2 infected with dengue virus serotype 4). The specificity of the test for nonflavivirus infections was 88% (3 of 26 positive), while for JE virus infections the specificity of the test was only 50% (10 of 20). However, most patients with secondary dengue virus infection were positive for both IgM and IgG antibodies to dengue virus, while no patients with JE virus infection had this profile, so cross-reactivity was only a concern for a small proportion of patients with secondary dengue infections. The rapid test demonstrated a good correlation with the reference EIA and HAI and should be useful for the rapid diagnosis of dengue virus infections.     

Evaluation of a New Test,GenoType HelicoDR,for Molecular Detection of Antibiotic Resistance in Helicobacter pylori

The eradication rate of Helicobacter pylori by standard therapy is decreasing due to antibiotic resistance, mainly to clarithromycin. Our aim was to provide a new molecular test to guide the treatment of new and relapsed cases. We first studied 126 H. pylori strains for phenotypic (MIC) and genotypic resistance to clarithromycin (rrl mutation) and levofloxacin (gyrA mutation) and then developed a DNA strip genotyping test on the basis of the correlation results and literature data. Clinical strains (n = 92) and gastric biopsy specimens containing H. pylori (n = 105) were tested blindly with the new molecular test GenoType HelicoDR. The presence of mutations or the absence of hybridization with wild-type sequences was predictive, in rrl for clarithromycin resistance in 91 cases (mostly the A2147G mutation) and in gyrA for levofloxacin resistance in 58 cases (mutations at codon 87 or 91). Genotyping revealed a mix of genotypes in 33% of the cases, reflecting a coinfection or selection for resistant mutants. The sensitivity and specificity of detecting resistance were 94% and 99% for clarithromycin and 87% and 98.5% for levofloxacin, respectively. The concordance scores were 0.96 for clarithromycin and 0.94 for levofloxacin. With global resistance rates of 46% for clarithromycin and 25% for levofloxacin, which were observed for consecutive positive biopsy specimens from 2007 and 2008, the positive and negative predictive values for detecting resistance were 99% and 94% for clarithromycin and 96% and 96% for fluoroquinolone. GenoType HelicoDR is efficient at detecting mutations predictive of antibiotic resistance in H. pylori when applied to strains or directly to gastric biopsy specimens.Helicobacter pylori infection is a common chronic gastric infection worldwide with one-third prevalence (6). About 1 out of 10 humans infected with H. pylori suffers from various digestive diseases, such as duodenal and gastric ulcer and nonulcer dyspepsia; 1 out of 100 develops gastric adenocarcinoma; and ≤1 out of 1,000 may develop gastric mucosa-associated lymphoid tissue lymphoma. All consensus guidelines recommend eradication of H. pylori (6, 20) in symptomatic patients. Standard therapy combines a proton pump inhibitor, such as omeprazole, and two antibiotics, chosen from among amoxicillin, clarithromycin, and metronidazole (20). This therapy was assessed in studies in the early 1990s and demonstrated an eradication rate of H. pylori of over 80%. However, the eradication rate is decreasing, with as low as 60% success in some countries, and this is related to the increase in clarithromycin and metronidazole resistance reported worldwide (9, 10, 17). Fluoroquinolones, such as levofloxacin and moxifloxacin, are often used for rescue therapy in a third- or fourth-line treatment (20, 31).Antibiotics used for the treatment of H. pylori infection are usually not chosen on the basis of routine susceptibility testing, because H. pylori is a fastidious microorganism requiring 3 to 10 days in a microaerobic atmosphere, and susceptibility results are not reliable for all antibiotics (17, 22). Indeed, susceptibility breakpoints have been difficult to set due to the lack of standard methods for susceptibility testing and difficulties in assessing the correlation between susceptibility results and clinical outcomes. Phenotypic resistance is correlated with clinical and microbiological failure for clarithromycin, but not for metronidazole (21). The eradication rate drops from 88% in the case of a clarithromycin-susceptible strain to less than 20% in the case of clarithromycin resistance (7, 21). Fluoroquinolone resistance was also shown to be correlated with treatment failure (24). Because resistance rates vary according to the country and patient characteristics, the choice of antibiotics on the basis of susceptibility results might be an effective strategy to improve H. pylori eradication. Since susceptibility testing is cumbersome, molecular methods for detection of resistance may be cost-effective.The mutations leading to resistance are now well known for macrolides and fluoroquinolones, although they are still unclear for metronidazole and amoxicillin. Clarithromycin resistance in H. pylori is due to point mutations in the rrl gene encoding the 23S rRNA, with three major mutations described: A2146C, A2146G, and A2147G (the numeration is from genome sequencing of NC000921 and NC000915, positions 2146 and 2147, formerly described as 2142 and 2143 [reviewed in references 21 and 22]). The resistance of H. pylori to quinolones is due to point mutations in the so-called quinolone resistance-determining region of the gyrA gene coding for the A subunit of the DNA gyrase, mainly at codons 87 and 91 (corresponding to 83 and 87 in Escherichia coli numbering) (1, 4, 23, 30).Our objective was to develop and implement a molecular method to easily detect mutations predictive of clarithromycin and fluoroquinolone resistance in H. pylori. We based our test on the DNA strip methodology used with success for other pathogens, such as Mycobacterium tuberculosis (13). We first designed a prototype test using a panel test of 126 H. pylori strains for which the MICs of clarithromycin and fluoroquinolones and the rrl and gyrA genotypes had been determined. Then, the new test was applied blindly to clinical strains and gastric biopsy specimens containing H. pylori, and the results were compared to those of susceptibility testing done routinely. The specificity of the new test for H. pylori was evaluated by testing strains of Helicobacter species other than H. pylori, as well as negative biopsy specimens. The new test was concordant with reference tests for 94 to 98% of the samples, either performed on isolated strains or directly on gastric biopsy specimens containing H. pylori, and was easy to perform.     

Diagnosis of Helicobacter pylori infection in adult and pediatric patients by using Pyloriset, a rapid latex agglutination test.

Pyloriset (Orion Diagnostica, Espoo, Finland) is a rapid antibody test using latex particles coated with acid-extracted antigen of Helicobacter pylori. We evaluated its ability to predict infection in 100 adult patients and 50 pediatric patients referred for gastric endoscopy. Sixty of 65 H. pylori-infected adults were correctly identified by the test. There were 12 false-positive and 5 false-negative reactions seen. Pyloriset had a sensitivity of 92% and a specificity of 66%. The positive predictive value was 83% and the negative predictive value 82%. In contrast, sensitivity dropped to 36% in the pediatric patients and the positive predictive value was only 40%. Pyloriset could become an important alternative to other more time-consuming diagnostic tests for H. pylori-infected adult patients but is inadequate for diagnosis of pediatric H. pylori infection.     

Laboratory Evaluation of a Dual Rapid Immunodiagnostic Test for HIV and Syphilis Infection

New dual tests for HIV and syphilis have been developed. Our study aimed to evaluate the laboratory performance of a dual rapid immunodiagnostic test for HIV and syphilis. Our evaluation showed high performance of this dual rapid test, which should be considered for implementation to increase screening coverage and efficiency.     

Clinical Evaluation of a Rapid Immunochromatographic Test for the Diagnosis of Dengue Virus Infection

A rapid immunochromatographic test was compared to the hemagglutination inhibition assay for separate determinations of dengue virus-specific immunoglobulin M (IgM) and IgG levels in paired serum specimens from 92 patients (34 with primary dengue virus infection, 35 with secondary dengue virus infection, and 23 without dengue virus infection). The rapid test showed 99% sensitivity in the diagnosis of dengue virus infection. The majority (30 of 34 [88%]) of patients with primary infection showed positive IgM but negative IgG, while 34 of 35 (97%) patients with secondary infection showed positive IgG with or without IgM. Specificity in nonflavivirus infections was 96% (1 of 23 positive). The rapid test should be a useful aid in rapid diagnosis of dengue virus infection.     

Field Evaluation of the InBios Chagas Detect Plus Rapid Test in Serum and Whole-Blood Specimens in Bolivia

Trypanosoma cruzi causes Chagas disease, which affects an estimated 7 million to 8 million people. Chagas disease is endemic throughout Latin America, with the highest prevalence in Bolivia. Conventional diagnosis requires a well-equipped laboratory with experienced personnel. We evaluated the Chagas Detect Plus (CDP) (InBios, Seattle, WA), a rapid immunochromatographic assay for IgG antibodies to T. cruzi. CDP performance was compared to infection status based on results obtained by indirect hemagglutination assay, immunofluorescent-antibody test, and enzyme-linked immunosorbent assay. Confirmed infection required positive results by at least 2 conventional assays. We used specimens from adults of both sexes in a general hospital in the city of Santa Cruz and from pregnant women in a hospital and children in villages in the Bolivian Chaco, an area of hyperendemicity. CDP was performed in paired whole-blood and serum specimens from 385 individuals in the two hospital studies and in 200 serum specimens from the community study. CDP showed sensitivities/specificities of 96.2% (95% confidence interval, 92.7 to 98.4)/98.8% (95.9 to 99.9) in whole blood and 99.3% (97.5 to 99.9)/96.9% (94.2 to 98.6) in serum, with no differences by sex, age group, or study site. CDP showed excellent sensitivity and specificity in our study population, comparable to those of conventional serology. The test is reliable for field surveys, requires no laboratory equipment, and performed well in serum and whole blood. The CDP could also be used for accurate maternal screening to identify neonates at risk of congenital transmission. CDP performance data in diverse geographic areas are needed to strengthen the evidence base for its use.     

Evaluation of a Helicobacter pylori Stool Antigen Test for the Diagnosis and Follow-Up of Infections in Children

 The aim of this study was to evaluate the performance of a newly developed enzyme immunoassay kit (HpSA) for detecting Helicobacter pylori antigens in the stool of children. This study was comprised of 58 children referred to various endoscopy units for evaluation of gastrointestinal symptoms and upper gastroduodenal endoscopy and 11 children for post-therapy follow-up. In the first group, 23 children were diagnosed as positive for Helicobacter pylori using bacteriological and/or histological methods. Stool antigens were detected in 20 of these positive patients, for a sensitivity of 86.9% and a negative predictive value of 91.9%. Since only one false-positive reaction was observed with the HpSA kit, the specificity was 97.1% and the positive predictive value 95.2%. Results obtained for post-therapy follow-up were also promising. The HpSA assays were negative for the eight children whose infections were eradicated after therapy, and a positive result was obtained for two of three patients who had a persistent infection.     

Improved Performance of a Rapid Office-Based Stool Test for Detection of Helicobacter pylori in Children before and after Therapy

A modified version of a rapid office based one-step monoclonal immunoassay for detection of Helicobacter pylori antigen in stool samples from children was evaluated against biopsy specimen-based methods and compared to a monoclonal enzyme immunoassay using the same antigen. Blinded stool samples from 185 children (0.3 to 18.2 years) were investigated at the time of upper endoscopy prior to anti-H. pylori therapy; 62 children were H. pylori infected and 123 noninfected according to predefined reference standards. Samples obtained 6 to 8 weeks after anti-H. pylori therapy were available from 58 children (3.8 to 17.7 years) and were compared to results of the [¹³C]urea breath test (14/58 were positive). The rapid stool tests were performed by two independent readers. Of 243 rapid tests performed, 1 (0.4%) was invalid for technical reasons. Equivocal results (very weak line) were reported 16 times by reader 1 and 27 times by reader 2. When equivocal results were considered positive, the two observers agreed on 76 positive and 160 negative results and disagreed on 7 samples (2.9%). The sensitivity was 90.8% for reader 1 and 85.5% for reader 2, and the specificity was 91.0% and 93.4%, respectively. The monoclonal enzyme immunoassay revealed a sensitivity and specificity of 94.7% and 97.6%, respectively. The modified chromatographic immunoassay is a good alternative in settings or situations when the monoclonal enzyme immunoassay or the [¹³C]urea breath test are not available or feasible. In order to improve sensitivity, very weak lines should be considered positive test results.Several noninvasive methods are available for the diagnosis of H. pylori infection (5, 14). Serological tests are not appropriate, since they cannot distinguish between a present and previous infection and, in addition, they have a low sensitivity in children younger than 12 years of age (6, 13). The [¹³C]urea breath test (UBT) is the preferred noninvasive diagnostic tool and gives excellent performance for both adults and children, but specificity decreases in very young and mentally disabled children who are not able to cooperate with the test procedure (10, 11, 25). So far, tests for detection of H. pylori antigen in stool samples are the only noninvasive diagnostic tools which do not show an age dependence for the diagnostic accuracy (14, 15). This makes stool tests very attractive, particularly for young children and for epidemiological studies. Several tests have been developed, but validation studies showed differences in performance. An enzyme immunoassay (EIA) based on polyclonal antibodies that was developed by the Meridian Company has been validated in several studies, with controversial results (17, 20, 24). Lack of accuracy is obviously related to intertest variability (19). In contrast, EIA based on monoclonal antibodies showed consistently excellent results, with very high sensitivity and specificity in both children and adults (15, 21). A meta-analysis with head-to-head comparison has judged the monoclonal EIA superior to the polyclonal EIA (8).Recently, we reported on the performance of a one-step monoclonal chromatographic immunoassay for detection of H. pylori antigen in stool samples from symptomatic children compared to the results of a well-established monoclonal EIA using the same antigen, namely, the catalase of H. pylori (22). Evaluation against biopsy specimen-based diagnostic methods showed a moderate sensitivity but a good specificity. After publication of the data, the manufacturer modified the tests. The aim of this study was to evaluate this new version of the rapid office-based one-step stool test in symptomatic children against invasive diagnostic methods and to compare the results with those of the monoclonal EIA.     

Diagnostic accuracy of a rapid whole-blood test for detection of Helicobacter pylori.

In this study, we evaluated a rapid whole-blood test, BM-test Helicobacter pylori, for detection of H. pylori infection in 144 and 48 patients with other gastrointestinal symptoms and with gastric cancer, respectively. The sensitivity, specificity, positive predictive value, negative predictive value, and diagnostic accuracy of the test correlated well with the standards used for the calculation, i.e., serology by enzyme-linked immunosorbent assay or culture and histology.     

Evaluation of a commercial immunoblot, Helicoblot 2.1, for diagnosis of Helicobacter pylori infection

The best method to diagnose Helicobacter pylori infection in different clinical situations is controversial. The aim of the study was to assess the performance of a commercial immunoblot, Helicoblot 2.1. The study comprised 215 patients, who were grouped according to the presence of H. pylori infection (assessed by two gastroscopies including histology with a median interval of 7.1 years, enzyme immunoassay [EIA]-based serology, and history of previous H. pylori infections and eradication therapies) into four categories: no H. pylori infection ever, previous infection, ongoing infection, and EIA seropositivity as the only marker of a possible previous infection. The sensitivity of Helicoblot 2.1 to show an ongoing or previous H. pylori infection was 100% and 92%, respectively. Helicoblot 2.1 was negative in only 80% of individuals with no evidence of present or previous infection but in 96% of patients 50 years of age or younger. The current infection marker of the immunoblot was positive in 49% of patients with successful H. pylori eradication therapy. After successful eradication therapy, Helicoblot 2.1 sustained positive results in 87% of patients, and CagA positivity was detected in 87% of patients with follow-up samples for more than 10 years after therapy. Helicoblot 2.1 is a sensitive and, among patients of ages 50 years or younger, a specific test in the primary diagnosis of H. pylori infection. However, it does not discriminate between past and current infections. It can be used in epidemiological studies assessing the role of H. pylori in different late sequelae.     

Clinical Evaluation of Rapid Diagnostic Test Kit Using the Polysaccharide as a Genus-Specific Diagnostic Antigen for Leptospirosis in Korea,Bulgaria, and Argentina

Leptospirosis, a zoonotic disease that is caused by many serovars which are more than 200 in the world, is an emerging worldwide disease. Accurate and rapid diagnostic tests for leptospirosis are a critical step to diagnose the disease. There are some commercial kits available for diagnosis of leptospirosis, but the obscurity of a species- or genus-specific antigen of pathogenic Leptospira interrogans causes the reduced sensitivity and specificity. In this study, the polysaccharide derived from lipopolysaccharide (LPS) of nonpathogenic Leptospira biflexa serovar patoc was prepared, and the antigenicity was confirmed by immunoblot and enzyme linked immunosorbent assay (ELISA). The performance of the rapid diagnostic test (RDT) kit using the polysaccharide as a diagnostic antigen was evaluated in Korea, Bulgaria and Argentina. The sensitivity was 93.9%, 100%, and 81.0% and the specificity was 97.9%, 100%, and 95.4% in Korea (which is a rare region occurring with 2 serovars mostly), Bulgaria (epidemic region with 3 serovars chiefly) and Argentina (endemic region with 19 serovars mainly) respectively. These results indicate that this RDT is applicable for global diagnosis of leptospirosis. This rapid and effective diagnosis will be helpful for diagnosis and manage of leptospirosis to use and the polysaccharide of Leptospira may be called as genus specific antigen for diagnosis.