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The ICER of C-UBT versus serology ranged from $57/cure to over $32270/cure in sensitivity analysis and ex­ceeded $2000/cure only with variation in C-UBT cost and serology specificity (Table 5). In no case did C-UBT domi­nate serology. However, serology became dominant over ¹³C-UBT when the specificity of ¹³C-UBT fell below 81%. Two-way sensitivity analysis: Because the use of serology to diagnose H pylori in low prevalence populations has been criticized for its low positive predictive value, the initial two-way sensitivity analysis assessed the influence of simul­taneous variation in H pylori prevalence and serology speci­ficity on the ICER of serology versus empirical ranitidine and ¹³C-UBT versus serology (Figure 3).

The ICER of the C-UBT versus serology fell to $352/cure, with a serology specificity of 70% and an H pylori prevalence of 10%. However, high serology specificity (95%) with H pylori prevalence greater than 30% caused the serology strategy to become dominant over ¹³C-UBT.

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RESULTS

Base case scenario: The number of endoscopies per 1000 pa­tients was lowest with the C-UBT strategy, higher with serology and highest with empirical ranitidine therapy (Table 3). The number of H pylori eradica­tion regimens prescribed per 1000 patients was lowest with empirical ranitidine (200.1), highest with serology and intermediate with the ¹³C-UBT.

In the base case scenario, the direct medical cost per pa­tient over 12 months was $598 in the ranitidine strategy, $635 in the C-UBT strategy and $603 in the serology strategy (Table 3). The number of H pylori-positive peptic ulcers cured was 53/1000 patients with the ranitidine strategy, 128/1000 patients with the ¹³C-UBT and 92/1000 patients with serology. No strategy demonstrated dominance over any other because none was both more effective and less costly (Figure 2). The ratio of total cost to total number of ul­cers cured was highest with ranitidine ($11,300/cure), inter­mediate with the serology strategy ($6,543/cure) and lowest with the ¹³C-UBT test and treat strategy ($4,945/cure).

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Several sources were used to estimate locally relevant direct costs for the resources consumed in the model (Table 2). Wholesale drug costs were determined through a survey of local pharmacies including the Hamilton Health Sciences Corporation (McMaster Site) Outpatient Phar­macy, Hamilton, Ontario. A 10% pharmacy markup was added to the wholesale price, as well as a dispensing fee of $4.11 per prescription ($6.11 minus a copayment of $2.00). Costs for physician services were taken from the 1998 On­tario Ministry of Health Schedule of Benefits.

The costs of outpatient endoscopy, endoscopic biopsy and RUT were derived from the Hamilton Health Sciences Corporation costing model, developed in accordance with the Ontario Case Cost Project (OCCP). The latter is a joint venture of the Ontario Ministry of Health and the Ontario Hospital Association, wherein each of 13 participating insti­tutions uses a standardized methodology to maintain a data­base of resource utilization and resource unit cost indexed by individual patient encounter. The cost of admission for management of complicated PUD was derived from a previ­ously published cost model based in part on the OCCP data­base.

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In each arm, the first-line regimen for H pylori eradication was omeprazole 20 mg, clarithromycin 500 mg and metroni­dazole 500 mg bid for seven days (OCM). The second-line regimen, used for OCM failures, was omeprazole 20 mg bid, clarithromycin 500 mg bid and amoxicillin 1000 mg bid for seven days. When a third attempt at H pylori eradication was necessary, ranitidine 150 mg bid, bismuth subsalicylate 524 mg qid, metronidazole 250 mg qid and tetracycline 500 mg qid were prescribed for two weeks. Probability inputs: Point estimates of path probabilities for the decision tree were extracted from a review of the pub­lished literature (Table 1). Articles were identified from computerized searches of the MEDLINE database (1966 to 1998) and from hand searches of recent review article bibli­ographies. For each probability, a plausible range of values for sensitivity analysis was chosen to reflect uncertainty in the literature. Where a necessary probability could not be found in the literature, a reasonable point estimate was cho­sen empirically and a wide range of plausible values was used for the sensitivity analysis.

The prevalence of H pylori infection among dyspeptic pa­tients was assumed to be 30% (range 10% to 50%). Among H pylori-positive patients, the prevalence of PUD was assumed to be 35% (20% to 50%) versus 3% among those without Hpylori. The sensitivity and specificity of the C-UBT for detection of H pylori were estimated at 96% and 98%, respectively (70% to 100%). The Hpy- lori serology assay was assigned a sensitivity of 85% and a specificity of 79% (70% to 95%) based on a published meta- analysis and a third-party technical review.

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Decision tree: The decision-analytic model was constructed using DATA software (TreeAge Software Inc, Williams- town, Massachusetts). A hypothetical cohort of 1000 pa­tients under the age of 50 years who had presented to their primary care practitioner with a new complaint of dyspepsia and did not use nonsteroidal anti-inflammatory drugs was used. Three initial management strategies were compared – empirical treatment with a four-week course of oral raniti- dine, H pylori testing using serology and H pylori testing using the ¹³C-UBT. Each strategy was evaluated with respect to costs and outcomes over a one-year period and from the viewpoint of a third-party payer for health care, considering only direct health care costs to the Ontario Ministry of Health. Health outcomes were quantified as the number of patients in whom H pylori-associated PUD was cured, in the sense that the ulcer was healed and the organism was eradi­cated.

In developing the path probabilities and management ap­proaches applied to the model, three simplifying assump­tions were made. First, it was assumed that gastric carcinoma would not develop in the hypothetical ‘low risk’ cohort. Sec­ond, it was assumed that endoscopy with antral biopsies for histology (including special stains for H pylori) and rapid urease testing was 100% accurate for the diagnosis of H pylori infection. Third, costs and outcomes up to and including only the first recurrence of symptoms were modelled, and the costs and consequences of subsequent episodes were not captured.

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UBT is considered by many to be the gold standard non- invasive test for the detection of active H pylori infection. After a 4 h fast, the patient ingests carbon- or carbon- labelled urea, which is metabolized to carbon dioxide by the H pylori-associated urease. The labelled carbon dioxide is then absorbed, and the increased concentration in expired air can be detected in a timed breath sample. When per­formed properly, the sensitivity and specificity of the UBT are well in excess of 95%. The widespread application of C-UBT has been limited, however, by its small atten­dant radiation exposure and the need for sample collection and analysis to be performed at appropriately licensed radio- isotope storage facilities, which often are only available to tertiary care centres. In contrast, carbon is a naturally oc­curring nonradioactive isotope that constitutes about 1.1% of normal expired carbon dioxide. Thus, breath samples for the C-UBT can be collected locally and mailed to a central commercial laboratory for analysis using a mass spectrome­ter. Although such equipment is expensive, the impact of the initial capital outlay on unit cost can be diminished by using a central facility to process large numbers of samples from peripheral centres.

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Test and treat strategies for Helicobacter pylori in uninvestigated dyspepsia: A Canadian economic analysis.

By convention, the term ‘dyspepsia’ is used to describe a symptom complex of chronic or recurrent pain or dis­comfort in the upper abdomen that is attributable to the up­per gastrointestinal tract. Although variably defined in the literature, dyspepsia imposes a substantial burden of illness. Population surveys suggest an annual prevalence of 25% to 29%, while practice audits reveal that dyspepsia ac­counts for 2% to 7% of primary care visits and 20% to 40% of gastroenterology consultations.

The new onset of dyspepsia in a previously asymptomatic individual can herald a variety of underlying organic disor­ders, including peptic ulcer disease (PUD), gastroesophageal reflux disease (GERD) and gastric carcinoma. However, the majority of patients who develop upper abdominal discom­fort have no endoscopic or radiographic evidence of peptic ulceration or reflux esophagitis, and are determined to have ‘functional’ or ‘nonulcer’ dyspepsia (NUD). Unfortunately, the precise character of an individual’s dyspepsia correlates poorly with underlying pathology and cannot discriminate PUD reliably from NUD. As a result, traditional manage­ment strategies have mandated either an empirical trial of antisecretory medication (eg, an H2-receptor antagonist) or early diagnostic imaging of the upper gastrointestinal tract.

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