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

Non-invasive diagnostic tests for Helicobacter pylori infection

BACKGROUND

Helicobacter pylori (H pylori) infection has been implicated in a number of malignancies and non-malignant conditions including peptic ulcers, non-ulcer dyspepsia, recurrent peptic ulcer bleeding, unexplained iron deficiency anaemia, idiopathic thrombocytopaenia purpura, and colorectal adenomas. The confirmatory diagnosis of H pylori is by endoscopic biopsy, followed by histopathological examination using haemotoxylin and eosin (H & E) stain or special stains such as Giemsa stain and Warthin-Starry stain. Special stains are more accurate than H & E stain. There is significant uncertainty about the diagnostic accuracy of non-invasive tests for diagnosis of H pylori.

OBJECTIVES

To compare the diagnostic accuracy of urea breath test, serology, and stool antigen test, used alone or in combination, for diagnosis of H pylori infection in symptomatic and asymptomatic people, so that eradication therapy for H pylori can be started.

SEARCH METHODS

We searched MEDLINE, Embase, the Science Citation Index and the National Institute for Health Research Health Technology Assessment Database on 4 March 2016. We screened references in the included studies to identify additional studies. We also conducted citation searches of relevant studies, most recently on 4 December 2016. We did not restrict studies by language or publication status, or whether data were collected prospectively or retrospectively.

SELECTION CRITERIA

We included diagnostic accuracy studies that evaluated at least one of the index tests (urea breath test using isotopes such as 13C or 14C, serology and stool antigen test) against the reference standard (histopathological examination using H & E stain, special stains or immunohistochemical stain) in people suspected of having H pylori infection.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened the references to identify relevant studies and independently extracted data. We assessed the methodological quality of studies using the QUADAS-2 tool. We performed meta-analysis by using the hierarchical summary receiver operating characteristic (HSROC) model to estimate and compare SROC curves. Where appropriate, we used bivariate or univariate logistic regression models to estimate summary sensitivities and specificities.

MAIN RESULTS

We included 101 studies involving 11,003 participants, of which 5839 participants (53.1%) had H pylori infection. The prevalence of H pylori infection in the studies ranged from 15.2% to 94.7%, with a median prevalence of 53.7% (interquartile range 42.0% to 66.5%). Most of the studies (57%) included participants with dyspepsia and 53 studies excluded participants who recently had proton pump inhibitors or antibiotics.There was at least an unclear risk of bias or unclear applicability concern for each study.Of the 101 studies, 15 compared the accuracy of two index tests and two studies compared the accuracy of three index tests. Thirty-four studies (4242 participants) evaluated serology; 29 studies (2988 participants) evaluated stool antigen test; 34 studies (3139 participants) evaluated urea breath test-13C; 21 studies (1810 participants) evaluated urea breath test-14C; and two studies (127 participants) evaluated urea breath test but did not report the isotope used. The thresholds used to define test positivity and the staining techniques used for histopathological examination (reference standard) varied between studies. Due to sparse data for each threshold reported, it was not possible to identify the best threshold for each test.Using data from 99 studies in an indirect test comparison, there was statistical evidence of a difference in diagnostic accuracy between urea breath test-13C, urea breath test-14C, serology and stool antigen test (P = 0.024). The diagnostic odds ratios for urea breath test-13C, urea breath test-14C, serology, and stool antigen test were 153 (95% confidence interval (CI) 73.7 to 316), 105 (95% CI 74.0 to 150), 47.4 (95% CI 25.5 to 88.1) and 45.1 (95% CI 24.2 to 84.1). The sensitivity (95% CI) estimated at a fixed specificity of 0.90 (median from studies across the four tests), was 0.94 (95% CI 0.89 to 0.97) for urea breath test-13C, 0.92 (95% CI 0.89 to 0.94) for urea breath test-14C, 0.84 (95% CI 0.74 to 0.91) for serology, and 0.83 (95% CI 0.73 to 0.90) for stool antigen test. This implies that on average, given a specificity of 0.90 and prevalence of 53.7% (median specificity and prevalence in the studies), out of 1000 people tested for H pylori infection, there will be 46 false positives (people without H pylori infection who will be diagnosed as having H pylori infection). In this hypothetical cohort, urea breath test-13C, urea breath test-14C, serology, and stool antigen test will give 30 (95% CI 15 to 58), 42 (95% CI 30 to 58), 86 (95% CI 50 to 140), and 89 (95% CI 52 to 146) false negatives respectively (people with H pylori infection for whom the diagnosis of H pylori will be missed).Direct comparisons were based on few head-to-head studies. The ratios of diagnostic odds ratios (DORs) were 0.68 (95% CI 0.12 to 3.70; P = 0.56) for urea breath test-13C versus serology (seven studies), and 0.88 (95% CI 0.14 to 5.56; P = 0.84) for urea breath test-13C versus stool antigen test (seven studies). The 95% CIs of these estimates overlap with those of the ratios of DORs from the indirect comparison. Data were limited or unavailable for meta-analysis of other direct comparisons.

AUTHORS' CONCLUSIONS

In people without a history of gastrectomy and those who have not recently had antibiotics or proton ,pump inhibitors, urea breath tests had high diagnostic accuracy while serology and stool antigen tests were less accurate for diagnosis of Helicobacter pylori infection.This is based on an indirect test comparison (with potential for bias due to confounding), as evidence from direct comparisons was limited or unavailable. The thresholds used for these tests were highly variable and we were unable to identify specific thresholds that might be useful in clinical practice.We need further comparative studies of high methodological quality to obtain more reliable evidence of relative accuracy between the tests. Such studies should be conducted prospectively in a representative spectrum of participants and clearly reported to ensure low risk of bias. Most importantly, studies should prespecify and clearly report thresholds used, and should avoid inappropriate exclusions.

Diagnosis of Helicobacter pylori infection

A number of invasive and non-invasive techniques are available for the diagnosis of infection with Helicobacter pylori. These can be used to establish whether infection is present and to confirm that eradication has been achieved after treatment. Invasive techniques require biopsy of the gastric mucosa; such techniques include histology, bacterial culture, the rapid urease test and the polymerase chain reaction (PCR) technique. The principal non-invasive techniques are the 13C-urea breath test and serological assays in serum or saliva samples. Histological examination of gastric biopsy samples should be mandatory at the initial presentation of the patient because it also gives insight on the status of the gastric mucosa. The rapid urease test can be used to give a rapid diagnosis of infection. Eradication should also be confirmed by histological examination, though other sensitive tests such as bacterial culture, PCR or the 13C-urea breath test may also be used.

[Study of the validity of "rapid" serology in diagnosing Helicobacter pylori infection]

OBJECTIVE

To evaluate prospectively the validity of a <<rapid>> serology diagnosis method (using capillary blood) in our ambit, taking for reference a combination of standard diagnostic methods.

DESIGN

Prospective. The endoscopist, pathologist and those responsible for interpreting the rapid urease test, the breath test and <<rapid>> serology did not know the results of the other diagnostic methods.

SETTING

Gastro-enterology service of a tertiary hospital.Participants. 30 consecutive patients with symptoms attributable to the upper digestive tract and who underwent an oral gastroscopy. Main measurements. Gastric biopsies for histology examination and for the rapid urease test and a breath test with 13C-urea were conducted. For <<rapid>> serology, the commercial SureStep HP WB test kit was used. A patient was considered infected when at least two of the three validated techniques (rapid urease test, histology, breath test) were positive; and not infected, when all three were negative.

RESULTS

30 patients, 30% male, with a mean age of 51, were included. The reference standard indicated 61% prevalence of infection, with two cases classed as undetermined. <<Rapid>> serology was positive in 8 patients and negative in 22. Sensitivity, specificity, positive predictive value and negative predictive value were, respectively, 41% (95% CI, 18-65), 91% (74-100), 87% (65-100) and 50% (28-72). The positive probability quotient was 4.5; and the negative, 0.65.

CONCLUSION

The <<rapid>> serology used in the current study has deficient diagnostic accuracy. Therefore, it should not be used in clinical practice to identify H. pylori infection.

Extending the reading time increases the accuracy of rapid whole blood test for diagnosis of Helicobacter pylori infection

BACKGROUND

To evaluate the accuracy of two rapid whole blood tests (the BM-Test Helicobacter pylori and the QuikPac IV One Step H. pylori Whole Blood Test), and compare this to a conventional quantitative ELISA test (HEL-p TEST II).

METHODS

Helicobacter pylori status in dyspeptic patients was assessed by culture, histology, and rapid urease tests on biopsies from the antrum and corpus. The optimal cut-off value of the reading time for the rapid blood tests was determined by using the receiver characteristics operative (ROC) curves.

RESULTS

In the 141 patients examined, 89 were infected, 51 were not infected, and one was indeterminate (only positive in either urease test or histology). Areas under ROC curves were greater in the BM-Test compared with the QuikPac IV (0.948 vs 0.840, P < 0.01), with their most appropriate cut-off reading times at 360 and 395 min, respectively, rather than 10 min as suggested by the manufacturer. The sensitivity and specificity were 94.4% and 94.1% at 360 min, and 74.2 and 96.1% at 10 min for the BM-Test; 80.9, 76.5 at 395 min and 3.4 and 100% at 10 min for the QuikPac IV. The antibody titer of the quantitative ELISA test was negatively correlated with the reaction time of the two rapid blood tests in H. pylori-infected patients (P < 0.05, r=-0.3).

CONCLUSIONS

The BM-Test is an appropriate office-based test for diagnosing H. pylori infection in Chinese patients. Extending the reading time would facilitate the readability of rapid blood tests with a resultant increase in accuracy.

Helicobacter pylori infection: epidemiology, pathophysiology, and therapy

Helicobacter pylori is one of the most commonly encountered human pathogens. It has been shown to be closely associated with peptic ulcer disease (PUD), gastric adenocarcinoma, and the gastric mucosa-associated lymphoid tissue (MALT) that may lead to gastric lymphoma. The current diagnostic methods include histology, microbiological culture, classic serology, urease activity detection, polymerase chain reaction (PCR) and stool antigen detection. Its treatment modality options are multiple; however, a triple regimen consisting of a proton pump inhibitor (PPI), and two antibiotics for 10 to 14 days is preferred. Drug resistance is a growing problem in this organism and new therapeutic options are currently limited.

Evaluation of rapid antibody tests for the diagnosis of Helicobacter pylori infection

OBJECTIVE

The aim of this study was to compare the performance characteristics of one serum and four whole blood rapid antibody tests for Helicobacter pylori infection.

METHODS

A total of 97 outpatients referred for endoscopic evaluation of dyspepsia were included. Antral biopsies were obtained for histology and rapid urease test. Serum was tested with an enzyme-linked immunoassay (HM-CAP) and a rapid serology test (FlexSure HP). A commercially available 13C-urea breath test was performed. Capillary blood obtained by fingerstick was tested with FlexSure HP, QuickVue, Accustat, and StatSimple pylori tests. Sensitivity, specificity, and accuracy of each rapid test was calculated relative to a criterion standard of histological gastritis and at least two of the four following tests positive: identifiable organisms on specially stained slides, rapid urease test, urea breath test, or serum immunoassay.

RESULTS

A total of 30 patients (31%) were infected. The FlexSure HP Serum, and FlexSure HP, QuickVue, Accustat, and StatSimple pylori whole blood tests had sensitivities of 90%, 87%, 83%, 76%, and 90%; specificities of 94%, 90%, 96%, 96%, and 98%, and accuracies of 93%, 88%, 92%, 87%, and 96%, respectively. Sensitivities were not statistically different. StatSimple pylori was more specific than FlexSure HP whole blood (p<0.03), and more accurate than FlexSure whole blood (p<0.024) and Accustat (p< 0.01). Serum immunoassay was significantly more sensitive (97%) than FlexSure whole blood, QuickVue, and Accustat (p<0.01), but its specificity (95%) was not statistically different from the rapid tests.

CONCLUSION

Rapid antibody testing provides an accurate diagnosis of H. pylori infection. In general, these tests are less sensitive than, but as specific as, standard serology.

Helicobacter pylori in the Canadian arctic: seroprevalence and detection in community water samples

OBJECTIVE

Many North American arctic communities are characterized by risk markers associated with Helicobacter pylori (H. pylori) infection, including overcrowded housing and inadequate water supply and sanitation systems. Our aim was to determine the seroprevalence of H. pylori infection in two traditional Inuit communities in the central Canadian arctic and to test for the presence of H. pylori, by polymerase chain reaction (PCR), in local water supplies.

METHODS

Samples of venous whole blood from adults and capillary blood from children were collected and analyzed by enzyme immunoassay and Helisal Rapid Test, respectively, for IgG antibody to H. pylori. Antibodies to CagA were detected by enzyme immunoassay, and ABO and Lewis antigens were also determined. Demographic and clinical information were collected by questionnaire. Water samples from each community were tested for H. pylori by PCR.

RESULTS

One hundred-thirty (50.8%) of 256 subjects from the two communities were positive for H. pylori IgG antibodies. Seropositive subjects were more likely to be male, compared with seronegative individuals (p = 0.01). Antibody status did not differ with respect to age, community, alcohol or cigarette use, number of persons per household, gastrointestinal complaints or previous investigations, medications, or presence of blood group O, Lewis a-b+. CagA antibodies were detected in 78 (61.9%) of 126 H. pylori-seropositive subjects tested; however, 41 (35.3%) of 116 H. pylori-seronegative subjects were also CagA positive. Water samples taken from the water delivery truck in Chesterfield Inlet and two lakes near Repulse Bay were positive for H. pylori.

CONCLUSION

The seroprevalence of H. pylori in the study group was higher than rates in southern Canadian populations, but lower than the seroprevalence previously documented in a Canadian subarctic Indian (First Nations) community. The detection of H. pylori in local water supplies may indicate a natural reservoir for the organism or possible contamination from human sewage.

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.