Alex Casalots

Accuracy of Diagnostic Tests for Helicobacter pylori: A Reappraisal

BACKGROUND Despite many changes, no large studies comparing the different diagnostic tests for Helicobacter pylori have been performed in the past 10 years. In this time, monoclonal stool antigen immunoassays and in-office 13C-urea breath tests (UBTs) have appeared. The aim of this study was to evaluate the accuracy of invasive and noninvasive tests in a large series of dyspeptic patients. METHODS A total of 199 dyspeptic patients who had not previously been treated for H. pylori infection were prospectively enrolled. Noninvasive analyses included a commercial infrared-based UBT and a commercially available stool test. Biopsy-based tests included histological examination and a rapid urease test. A patient was considered to be infected when at least 2 test results were positive. Sensitivity, specificity, positive and negative predictive values, and 95% confidence intervals were calculated. The test results were compared using the McNemar test. RESULTS Rates of positive test results were similar (54%) for the rapid urease test, histopathological examination, and the stool test. By contrast, 75% of UBT results were positive, and the UBT was associated with a very low specificity (60%). For this reason, the delta cutoff value for the UBT was recalculated as 8.5%. Sensitivities and specificities with this new cutoff value were 95% and 100%, respectively, for the rapid urease test; 94% and 99%, respectively, for histopathological examination; 90% and 93%, respectively, for the stool test; and 90% and 90%, respectively, for the UBT. CONCLUSIONS Histological examination and rapid urease testing showed excellent diagnostic reliability. The stool test seems to be a good, noninvasive alternative to endoscopy-based tests. By contrast, the infrared-based UBT evaluated in our study showed a lower than expected performance, which was partially corrected when the cutoff value for the test was recalculated.

Real-Time PCR Improves Helicobacter pylori Detection in Patients with Peptic Ulcer Bleeding

Background and Aims Histological and rapid urease tests to detect H. pylori in biopsy specimens obtained during peptic ulcer bleeding episodes (PUB) often produce false-negative results. We aimed to examine whether immunohistochemistry and real-time PCR can improve the sensitivity of these biopsies. Patients and Methods We selected 52 histology-negative formalin-fixed paraffin-embedded biopsy specimens obtained during PUB episodes. Additional tests showed 10 were true negatives and 42 were false negatives. We also selected 17 histology-positive biopsy specimens obtained during PUB to use as controls. We performed immunohistochemistry staining and real-time PCR for 16S rRNA, ureA, and 23S rRNA for H. pylori genes on all specimens. Results All controls were positive for H. pylori on all PCR assays and immunohistochemical staining. Regarding the 52 initially negative biopsies, all PCR tests were significantly more sensitive than immunohistochemical staining (p<0.01). Sensitivity and specificity were 55% and 80% for 16S rRNA PCR, 43% and 90% for ureA PCR, 41% and 80% for 23S rRNA PCR, and 7% and 100% for immunohistochemical staining, respectively. Combined analysis of PCR assays for two genes were significantly more sensitive than ureA or 23S rRNA PCR tests alone (p<0.05) and marginally better than 16S rRNA PCR alone. The best combination was 16S rRNA+ureA, with a sensitivity of 64% and a specificity of 80%. Conclusions Real-time PCR improves the detection of H. pylori infection in histology-negative formalin-fixed paraffin-embedded biopsy samples obtained during PUB episodes. The low reported prevalence of H. pylori in PUB may be due to the failure of conventional tests to detect infection.

Transanal endoscopic surgery with total wall excision is required with rectal adenomas due to the high frequency of adenocarcinoma.

BACKGROUND: Colorectal adenomatous polyps are considered premalignant lesions, although a high percentage are already malignant at the time of their removal. Full-thickness excision in patients with adenoma detected in preoperative biopsy enables much more accurate pathology examination and has shown that local surgery is appropriate for T1 adenocarcinoma. OBJECTIVE: To determine whether full-thickness excision during transanal endoscopic surgery is the treatment of choice for rectal adenoma, and to identify possible predictors of invasive adenocarcinoma associated with this type of lesion. DESIGN: Prospective, observational study. SETTING: The study was conducted at a university teaching hospital. PATIENTS: All patients scheduled for transanal endoscopic surgery after detection of adenoma in a preoperative biopsy between June 2004 and February 2013 entered the study. MAIN OUTCOME MEASURES: The principal variable was the presence of invasive adenocarcinoma in the pathology study. Other study variables were the epidemiological variables sex and age; the clinical variables tumor size, number of quadrants affected, distance from the anal verge, and tumor location; and the morphological variables tumor aspect, degree of dysplasia, preoperative biopsy (tubulo-villous), endorectal ultrasound, and pelvic MRI stage. Variables found to be related to the risk of malignancy in rectal adenomas were evaluated using univariate and multivariate analysis. RESULTS: Of 471 patients who underwent surgery, 277 had a preoperative diagnosis of adenoma. Final pathology studies showed 52 (18.8%) invasive adenocarcinomas, among which 27 were pT1 (52%), 16 pT2 (30.7%), and 9 pT3 (17.3%). Factors predictive of invasive adenocarcinoma were sessile morphology (OR 3.2, 95%CI 1.4–7.1), high-grade dysplasia (OR 2.3, 95%CI 1.2–4.8), and endorectal ultrasound stage uT2-T3 (OR 3.8, 95%CI 1.6–9). LIMITATIONS: The limitations are derived from the observational design. CONCLUSIONS: In this sample, half of the adenocarcinomas from adenomas were T1 adenocarcinomas. Because a high proportion of rectal adenomas are, in fact, invasive adenocarcinomas, full-thickness excision is appropriate.

microRNA profiling in duodenal ulcer disease caused by Helicobacter pylori infection in a Western population

Although the connection of microRNAs (miRNAs) to some diseases is well established, their involvement in chronic infections such as Helicobacter pylori has received less attention. The aim was to compare miRNA expression profiling in patients with duodenal ulcer (DU) due to H. pylori infection with that in infected patients without DU and in uninfected patients. The miRNA expression profile was determined by microarrays in antral mucosal samples from well-characterized dyspeptic patients (n = 46). The most significant set of miRNAs was subsequently analysed in an independent validation group of patients (n = 42). Transcripts for IL8, IL12p40, IL12p35 and IL23p19, the signalling molecules MYD88, GATA6, SOCS2 and STAT6 and H. pylori virulence factors cagA and VacA were analysed. Microarray experiments showed that 17 miRNAs were deregulated in the mucosa of H. pylori-infected patients. No significant differences were observed between normal and DU patients. PCR confirmed the up-regulation of miR-9, miR-146a, miR-155 and miR-650 and the down-regulation of miR-96 and miR-204 in the independent validation set of patients. Importantly, miR-9, miR-96, miR-146a and miR-650 expression was specific to chronic-active gastritis. H. pylori-infected patients showed higher levels of IL8 and IL12p40 mRNAs and lower levels of GATA6 and SOCS2 mRNAs. The antral mucosa of patients with non-active or chronic-active gastritis showed significantly lower levels of GATA6, MYD88, SOCS2 and STAT6 mRNAs compared with patients without gastritis. The down-regulation of these factors was not correlated with the expression of any of the validated miRNAs. The exact role of the miRNA changes observed will require further study.

Occult H. pylori infection partially explains ‘false-positive’ results of 13C-urea breath test

Background In a previous study, UBiT-100 mg, (Otsuka, Spain), a commercial 13C-urea breath test omitting citric acid pre-treatment, had a high rate of false-positive results; however, it is possible that UBiT detected low-density ‘occult’ infection missed by other routine reference tests. We aimed to validate previous results in a new cohort and to rule out the possibility that false-positive UBiT were due to an ‘occult’ infection missed by reference tests. Methods Dyspeptic patients (n = 272) were prospectively enrolled and UBiT was performed, according to the manufacturer’s recommendations. Helicobacter pylori infection was determined by combining culture, histology and rapid urease test results. We calculated UBiT sensitivity, specificity, positive and negative predictive values (with 95% CI). In addition, we evaluated ‘occult’ H. pylori infection using two previously-validated polymerase chain reaction (PCR) methods for urease A (UreA) and 16 S sequences in gastric biopsies. We included 44 patients with a false-positive UBiT, and two control groups of 25 patients each, that were positive and negative for all H. pylori tests. Results UBiT showed a false-positive rate of 17%, with a specificity of 83%. All the positive controls and 12 of 44 patients (27%) with false-positive UBiT were positive for all two PCR tests; by contrast, none of our negative controls had two positive PCR tests. Conclusions UBiT suffers from a high rate of false-positive results and sub-optimal specificity, and the protocol skipping citric acid pre-treatment should be revised; however, low-density ‘occult’ H. pylori infection that was undetectable by conventional tests accounted for around 25% of the ‘false-positive’ results.