Medical Inspection – Health Blog

A total of 103 patients were initially enrolled in the study. Of these, 51 were in the omeprazole once daily arm and 52 were allocated to the omeprazole twice daily arm. Three patients were lost to follow-up immediately after the first visit and were excluded because it was not known whether any medi­cations had been taken. Two of these were from the omeprazole once daily arm and one was from the omeprazole twice daily arm. Thus, the total ITT population was 49 in the omeprazole once daily arm and 51 in the omeprazole twice daily arm. Demographic data were similar in both ITT groups (Table 1). Patient diagnoses were not significantly different by %² (P=0.23), and sex distribution was the same (P=0.43).

Three patients in the omeprazole once daily arm took all their medications but did not have a final assessment and were excluded from the APT analysis but included in the ITT analysis. Reasons for drop out were that one patient was too busy and refused any final assessment, one moved away and the last was unreachable despite many attempts. Two patients in the omeprazole once daily arm took only half of their metronidazole pills by error. Because they were non- compliant, they were excluded from PP analysis, but a final assessment was available in both. H pylori was eradicated in one and persisted in the other. The patient in whom H pylori persisted was the only patient in this arm who had also re­ceived previous treatment and had received omeprazole and clarithromycin dual therapy.

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Patients were recruited from a single gastroenterology prac­tice in Guelph, Ontario. Guelph has 94,000 inhabitants and is located near several large academic medical centres. In this community, it is not possible to culture H pylori and perform antibiotic susceptibility testing. The nearest centre perform­ing C urea breath tests is a large teaching centre in Hamil­ton, Ontario, 45 km from Guelph. The C-urea breath test was not readily available when this study was performed. The study was approved by the ethics review committee of the Guelph General Hospital.

Patients referred to the practice and subjected to endos- copy for evaluation had two antral and two body biopsies to confirm H pylori infection. Patients were invited to partici­pate in this open cohort study if they were positive for H pylori by histology using the Geimsa stain. All patients gave written informed consent.

Patient diagnosis of inactive duodenal or gastric ulcer dis­ease (considered collectively as peptic ulcer disease), gastro- esophageal reflux disease and nonulcer dyspepsia were recorded. Inclusion criteria were 18 to 80 years of age and histologically proven H pylori infection. Patients who had taken antibiotics in the previous month, females who were pregnant or lactating, sexually active females in reproduc­tive years who did not have adequate contraception and any patient currently involved in another clinical trial were ex­cluded. Eligible patients were randomly assigned in this un- blinded, cohort study to one of two regimens – seven days of treatment with clarithromycin 250 mg and metronidazole 500 mg bid in combination with omeprazole 20 mg, either once or twice daily.

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In 1993, Bazzoli introduced the highly effective Helicobacter pylori eradication regimen of omeprazole 20 mg once daily, clarithromycin 250 mg bid and tinidazole 500 mg bid for one week. However, tinidazole is not avail­able in Canada. Since that time, many other studies using a proton pump inhibitor (PPI) in combination with clarithromycin and another nitroimidazole, metronidazole, have been reported with consistent efficacy. The first of these was the landmark MACH 1 study, which used omeprazole 20 mg bid with clarithromycin 250 mg bid and metronidazole 400 mg bid for one week to achieve 94.3% eradication. Subgroup analysis of the Canadian patients in this study demonstrated that results were the same as for the European patients. In Canada, the 400 mg dose of metronidazole is not available; however, the 500 mg dose is as effective. Other PPIs such as lansoprazole and pantoprazole have similar efficacy.

Due to its efficacy, European and Canadian H pylori consensus conferences have recommended that triple therapy with a PPI, clarithromycin and metronidazole be one of the first line therapies for H pylori eradication. The Maastricht Consensus Report considered tinidazole and metronidazole to be interchangeable.

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While the use of standard QCT has been based on two-dimen­sional characterization of vertebral trabecular bone, three-dimen­sional, or volumetric QCT, are new techniques that allow to im­prove spinal measurements and to extend QCT assessments to the proximal femur. They encompass the entire object of interest with stacked slices, or spiral CT scans, and can use anatomic landmarks to automatically generate relevant projections. Volu­metric QCT can not only determine BMD of the entire bone or subregion, such as a vertebral body or femoral neck, it can also provide separate analysis of the trabecular or cortical compo­nents. Because a true and highly accurate volumetric rendering is provided, important geometrical and biomechanically relevant assessments can be derived, such as cross-sectional moment of inertia and finite element analysis. A lateral scout view covering T11-L5 is first employed to delin­eate the lumbar spine vertebral levels. To relate the CT mea­surements to BMD, patients are scanned simultaneously with a bone mineral reference phantom containing calibration objects with equivalent densities to those of calcium hydroxyapatite.

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QCT can be performed in single-energy (SEQCT) or dual-energy (DEQCT) modes. These two techniques differ in accuracy, preci­sion, and radiation. Variable marrow fat composition in the verte­brae, accuracy of the calibration standard and beam hardening errors and scatter, among other factors, contribute to the accura­cy of SEQCT for spinal bone mineral determination. Marrow fat is the principal source of error, because it causes SEQCT measure­ments to underestimate bone mineral density (BMD) and overes­timate BMD loss. Marrow fat increases with age producing an in­creasingly large error in the accuracy of spine QCT measure­ments in older patients. The presence of marrow fat results in an underestimation of bone density in the young of about 20 mg/cm³ and as much as 30 mg/cm³ in the elderly, so that QCT has an ac­curacy from 5 to 15%, depending on the percentage of marrow fat and the age of the patient. However it is possible to use a simple correction procedure that takes this into account reducing the BMD accuracy errors to levels that are small compared with the biological variation. Additionally, we can also reduce the er­rors caused by marrow fat by using a kVp setting that minimizes the fat sensitivity for a particular scanner. DEQCT too improves accuracy, but this approach incurs poorer in vivo precision and higher radiation dose, so that it is recommended only for research studies that require higher accuracy.

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QCT is a X-ray absorptiometric technique such as SXA, and DXA (Single and Dual X-ray Absorptiometry), but it is different from these methods of measurement because it provides sepa­rate estimates of trabecular and cortical bone BMD as a true vol­umetric mineral density in mg/cm³. It measures high-turnover trabecular bone in consecutive vertebrae of the spine (usually two to four vertebrae out of T12 to L4), using commercial CT scanners and a bone mineral reference standard to calibrate each scan. Beginning from an initial lateral localized image and using a low-dose technique with the gantry angled parallel to the vertebral end plate, single 8 to 10 mm-thick sections are ob­tained through the midplane of each of these vertebrae (Fig. 1). A region of interest (ROI) is manually positioned in the anterior portion of trabecular bone of the vertebral body for analysis. It is possible to automate the sagittal location of midvertebral slices and the axial placement of ROIs to improve precision and reduce acquisition and analysis time. A software automatically locates the vertebral body, maps its outer edges, and employs anatomic landmarks, such as the spinous process and spinal canal and it calculates in this way size and location of the ROIs. Either trabecular, cortical, or integral (cortical and trabecular) bone ROIs are defined by these systems. The basivertebral vein and sclerotic foci such as bone islands have to be excluded. Hounsfield units (HU) (also known as CT number) are used to measure the CT density of the selected area of interest within a slice through a vertebral body. Then, comparing the CT number of the trabecular bone to that of the compartments of the calibra­tion standard, it is possible to achieve a conversion to mg/cm³. The calculated densities for the vertebrae are averaged and compared to those of a normal population. Normative data are gender-and race-specific.

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