Transcranial Doppler Ultrasound Detection of Microemboli as a Predictor of Cerebral Events in Patients with Symptomatic and Asymptomatic Carotid Disease: A Systematic Review and Meta-Analysis.

OBJECTIVE: Identification of patients who will benefit from carotid endarterectomy is not entirely effective, primarily utilising degree of carotid stenosis. This study aimed at determining if microembolic signals (MES) detected by transcranial Doppler ultrasound (TCD) can provide clinically useful information regarding stroke risk in patients with carotid atherosclerosis. METHODS: A meta-analysis of prospective studies was performed. Three analyses were proposed investigating MES detection as a predictor of: stroke or TIA, stroke alone, and stroke or TIA but with an increased positivity threshold. Subgroup analysis was used to compare pre-operative (symptomatic or asymptomatic) patients and peri- or post-operative patients. RESULTS: Twenty-eight studies reported data regarding both MES status and neurological outcome. Of these, 22 papers reported data on stroke and TIA as an outcome, 19 on stroke alone, and eight on stroke and TIA with increased positivity threshold. At the median pre-test probability of 3.0%, the post-test probabilities of a stroke after a positive and negative TCD were 7.1% (95% CI 5-10.1) and 1.2% (95% CI 0.6-2.5), respectively. In addition, the sensitivities and specificities of each outcome showed that increasing the threshold for positivity to 10 MES per hour would make TCD a more clinically useful tool in peri- and post-operative patients. CONCLUSION: TCD provides clinically useful information about stroke risk for patients with carotid disease and is technically feasible in most patients. However, the generally weak level of evidence constituting this review means definitive recommendations cannot be made.

Multilaboratory comparison of proficiencies in susceptibility testing of Helicobacter pylori and correlation between agar dilution and E test methods.

Susceptibility testing was performed at seven Canadian microbiology laboratories and the Helicobacter Reference Laboratory, Halifax, Nova Scotia, Canada, to assess susceptibility testing proficiency and the reproducibility of the results for clarithromycin and metronidazole and to compare the Epsilometer test (E test) method to the agar dilution reference method. Control strain Helicobacter pylori ATCC 43504 (American Type Culture Collection) and 13 clinical isolates (plus duplicates of four of these strains including ATCC 43504) were tested blindly. The National Committee for Clinical Laboratory Standards (NCCLS) guidelines for agar dilution testing were followed, and the same suspension of organisms was used for agar dilution and E test. Antimicrobials and E test strips were provided to the investigators. Methods were provided on a website (www.Helicobactercanada.org). Each center reported MICs within the stated range for strain ATCC 43504. Compared to the average MICs, interlaboratory agreements within 2 log(2) dilutions were 90% (range, 69 to 100%) for clarithromycin by agar dilution, with seven very major errors [VMEs], and 85% (range, 65 to 100%) by E test, with three VMEs. Interlaboratory agreements within 2 log(2) dilutions were 83% (range, 50 to 100%) for metronidazole by agar dilution, with six VMEs and eight major errors (MEs), and 75% (range, 50 to 94%) by E test, with four VMEs and four MEs. At lower and higher concentrations of antibiotic, E test MICs were slightly different from agar dilution MICs, but these differences did not result in errors. When a standardized protocol based on NCCLS guidelines was used, most participants in this study correctly identified clarithromycin- and metronidazole-susceptible and -resistant strains of H. pylori 93% of the time by either the agar dilution or E test method, and the numbers of errors were relatively equivalent by both methods.

Association of Helicobacter pylori genotype with gastroesophageal reflux disease and other upper gastrointestinal diseases.

OBJECTIVE: Helicobacter pylori (H. pylori) is a recognized pathogen, but it may also have a protective effect for gastroesophageal reflux disease (GERD). We compared the prevalence of potential virulence factors (cagA, cagE, vacA genotypes) in GERD to other upper gastrointestinal diseases and controls. METHODS: A total of 405 patients underwent gastroscopy with H. pylori isolation and serum testing. Patient diagnostic subgroups were prospectively defined. Genotypes were determined by amplification using polymerase chain reaction. CagA antibodies were determined by western blot, enzyme-linked immunosorbent, and flow microsphere immunofluorescent assays. RESULTS: Patients were grouped as follows: nonulcer dyspepsia (26%), GERD (20%), gastric ulcer (17%), duodenal ulcer (12%), gastric cancer (6%), or controls (19%). The cagA gene was present in 94-97% of subjects in all categories, but the cagA antibody was less prevalent in nonulcer dyspepsia (69%, 95% CI: 48-86%, p = 0.02) and GERD (69%, CI: 39-91%, p < 0.05) than in those with gastroduodenal pathology including gastric ulcer, duodenal ulcer, and gastric cancer (92%, CI: 81-98%). The cagE gene and vacA S1 genotype were more frequent in patients with gastroduodenal pathology (p < 0.01). GERD was associated with a significantly lower rate of vacA S1 genotype than controls (29% (CI: 10-56%) versus 80% (CI: 59-93%), p < 0.01). The vacA S1 genotype was associated with the presence of cagA antibodies. CONCLUSIONS: The cagE and vacA S1 genotypes are more prevalent in patients with peptic ulcer or gastric cancer, suggesting a potential function in virulence for these genes. However, the vacA S1 genotype was also more prevalent in controls than GERD, suggesting a potential protective effect against GERD.

Helicobacter pylori: primary susceptibility to clarithromycin in vitro in Nova Scotia.

Resistance to antimicrobial agents is a major determinant of the efficacy of regimens to eradicate Helicobacter pylori. Clarithromycin (CLA) has become one of the most commonly used antibiotics for treatment of H pylori infection. In this study, the rate of primary resistance to CLA in H pylori isolated from patients was determined. One hundred sixty-two strains were recovered from patients before treatment. Strains were grown and inoculated onto Mueller-Hinton agar with 7% sheep blood. CLA epsilometer gradient agar diffusion test (E test) strips were used to test for susceptibility. Appropriate control organisms were tested to validate the assay. Plates were incubated at 37 degrees C in a microaerophilic atmosphere for up to five days. E test results were easy to interpret. Strains were considered resistant if the minimum inhibitory concentration (MIC) was 2 micrograms/mL or greater. Three strains were resistant (two strains with MIC 8 micrograms/mL and one strain with MIC 12 micrograms/mL) and 159 strains were sensitive (MICs ranged from less than 0.016 to 0.38 micrograms/mL). Ninety per cent of the strains had MICs of 0.023 micrograms/mL. Primary resistance was 1.8%. These susceptibility data support the use of CLA for the treatment of H pylori in the Nova Scotia population.

Serological detection of Helicobacter pylori antibodies in children and their parents.

The antibody response to Helicobacter pylori was examined in 56 children (ages 5 to 18) to determine whether serological tests can be used for diagnosis. Twenty-four children (43%) were H. pylori positive and 32 children (57%) were H. pylori negative by culture and histological examination of endoscopic biopsy specimens. The immune response was also examined in 39 nonendoscoped parents of the children. H. pylori-specific immunoglobulin G (IgG) and IgA antibodies were detected by the flow microsphere immunofluorescent assay (FMIA). IgG was also detected by using the Pyloristat enzyme-linked immunosorbent assay (ELISA). The sensitivity, specificity, and positive and negative predictive values for the FMIA for IgG were 100, 97, 96, and 100%, respectively. The respective values for the Pyloristat ELISA for IgG were 96, 94, 92, and 97%. The respective values for the FMIA for IgA were 50, 100, 100, and 73%. Both assays identified the same 19 parents as IgG positive, while FMIA identified 17 of the 19 parents as IgA positive.

Increasing prevalence of Helicobacter pylori infection with age: continuous risk of infection in adults rather than cohort effect.

It remains unclear whether acquisition of Helicobacter pylori is due to a continuous risk of acquiring the infection or a cohort effect. In this prospective 3-year cohort study, the seroprevalence, conversion, and reversion of H. pylori infection as determined by IgG antibodies was examined. The cohort consisted of 316 randomly selected, nonpatient subjects aged 18-72 years who each provided at least 2 suitable samples. Seroprevalence of H. pylori increased from 21% in the third decade to 50% in the eighth decade. Crude annual seroconversion rate was 1% and the "spontaneous" seroreversion rate was 1.6%. Age was the only identified risk factor for H. pylori infection. A continuous risk of acquisition of 1%/year rather than a cohort effect best explains the pattern of H. pylori infection in this Canadian population. Seroconversion continues in adult life, and spontaneous reversions do occur, especially in the later decades.

Serological detection of Helicobacter pylori by a flow microsphere immunofluorescence assay.

A flow cytometric immunofluorescence assay (FMIA) for the detection of immunoglobulin G antibodies to Helicobacter pylori was developed. A multicomponent antigen was prepared and used to coat carboxylated polystyrene microspheres for reaction with patient sera followed by fluorescein isothiocyanate-labelled goat anti-human immunoglobulin G. The reacted microspheres were collected with a flow cytometer, and fluorescence was quantitated relative to the cutoff value provided by pooled sera from patients in whom H. pylori could not be demonstrated by culture or histology. Serum samples from 28 H. pylori-positive patients and 27 H. pylori-negative patients were tested by FMIA. Additionally, an in-house enzyme-linked immunosorbent assay (ELISA) employing the same antigen preparation and a commercially available ELISA were used to assay the patient population. Both the FMIA and in-house ELISA were 100% sensitive and 89% specific with positive and negative predictive values of 90 and 100% and no equivocal results. The commercial ELISA was 96% sensitive and 89% specific with positive and negative predictive values of 90 and 96% and five equivocal results. FMIA provides a rapid, inexpensive, and easily performed means for serodiagnosis of H. pylori.