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Clinical and economic assessment of the omeprazole test in patients with symptoms suggestive of gastroesophageal reflux disease |
Fass R, Ofman J J, Gralnek I M, Johnson C, Camargo E, Sampliner R E, Fennerty M B |
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Record Status This is a critical abstract of an economic evaluation that meets the criteria for inclusion on NHS EED. Each abstract contains a brief summary of the methods, the results and conclusions followed by a detailed critical assessment on the reliability of the study and the conclusions drawn. Health technology The use of omeprazole test (40 mg AM + 20 mg PM for 7 days) as a noninvasive strategy in the diagnosis of gastroesophageal reflux disease (GERD) in patients with typical GERD symptoms.
Economic study type Cost-effectiveness analysis.
Study population Patients with typical GERD symptoms.
Setting Primary and secondary care. The economic study was carried out in the USA.
Dates to which data relate Effectiveness data related to the noninvasive strategy were collected between 1 January 1996 and 31 December 1996. Effectiveness data related to the invasive strategies were obtained from reports published between 1982 and 1992. Resource use data and the corresponding date of data collection were not reported. Cost data were obtained from 1998 sources. The fiscal year was 1998.
Source of effectiveness data Effectiveness data were derived from a single study and a review of the literature.
Link between effectiveness and cost data Costing was not performed on the same patient sample as that used in the effectiveness analysis and was carried out retrospectively.
Study sample Power calculations were not used to determine the sample size. The study sample consisted of 43 patients with a mean (SD) age of 55.2 (2.0) years and a range of 26 to 75 years. Before the commencement of the randomization the patients underwent upper endoscopy and ambulatory 24-hour esophageal pH monitoring. The results of which were not revealed to the patients until the study completion and were used to classify patients as GERD-positive (n=35 with an average age of 55 years) or GERD-negative (n=7 with an average age of 56.4 years). GERD-positive and GERD-negative patients were randomized to initially receive omeprazole (40 mg AM + 20 mg PM for 7 days) followed by the similar dose of placebo for 7 days, or placebo at first followed by omeprazole.
Study design The study was a randomized, double-blind, placebo-controlled, crossover trial. The number of centres involved in the study was not specified. The duration of the study time frame was a minimum of three months. The loss to follow-up was 2% (1 patient). A block size of 4 was used for stratified block randomization. To minimise the carryover effect, a washout period was designed to occur in the third study week.
Analysis of effectiveness The principle used in the analysis of effectiveness was treatment completers only. The outcome measures were the sensitivity, specificity, positive and negative predictive values, and accuracy of the omeprazole test. The detection of positive cases in the test was based on 50% (or 75%) improvement relative to the baseline assessment in the heartburn score. Patients kept symptom records by completing a daily symptom diary. The severity of symptom scale (mild, 1; moderate, 2; severe, 3; and disabling, 4) and the daily frequency values were used to calculate symptom score. The Mann-Whitney test was used to investigate period and treatment effects. The cases of adverse effects were reported.
Effectiveness results The sensitivity of the omeprazole test was 80% (95% CI: 66.7%-93.3%) and the specificity was 57.1% (95% CI: 20.5%-93.8%), based on a response rate of 28 from 35 GERD positive patients and 3 from 7 GERD negative patients.
The positive predictive values were 90.3% (95% CI: 79.9%-100%) and the negative predictive values, 36.4% (95% CI: 7.9%-64.8%).
The overall accuracy of the omeprazole test was 76.2%.
When 75% improvement in heartburn was used as the threshold, the corresponding values of sensitivity were 85.7%, positive predictive value was 90.9%, and accuracy of the test was 81%.
Adverse effects occurred in 2 GERD-positive and 1 GERD-negative patients, two cases of diarrhoea and 1 case of diarrhoea plus abdominal pain being reported.
Clinical conclusions The omeprazole test seemed to be a sensitive tool for detecting GERD as the cause of heartburn symptoms, in 80% of patients.
Modelling A decision analytic model was constructed using DATA decision analysis software to evaluate the cost-effectiveness of alternative strategies by estimating the financial and clinical outcomes for 1 year.
Outcomes assessed in the review The outcomes assessed in the review were the sensitivity and specificity of upper endoscopy and ambulatory 24-hour esophageal pH monitoring.
Study designs and other criteria for inclusion in the review Sources searched to identify primary studies The MEDLINE computerised bibliographic database was searched.
Criteria used to ensure the validity of primary studies Methods used to judge relevance and validity, and for extracting data Number of primary studies included A total of 3 studies were included.
Methods of combining primary studies In cases where a range of values were found for the outcome measures, values with bias in favour of the traditional strategies were chosen.
Investigation of differences between primary studies Results of the review The sensitivity of upper endoscopy was 50% and specificity was 95%.
The sensitivity of ambulatory 24-hour esophageal pH monitoring was 70% and specificity was 80%.
Measure of benefits used in the economic analysis The measure of benefit was accuracy of diagnosis.
Direct costs Costs were not discounted as they were incurred over a period of one year. Quantities of resource use were not reported in detail and separately from costs. The cost analysis covered the costs of upper endoscopy, ambulatory 24-hour esophageal pH monitoring, omeprazole test, and omeprazole healing and maintenance course (course of 20 mg/d for the remainder of 1 year). The perspective in the cost analysis was that of a third-party payer. The sources of cost data were Medicare Fee Schedule and Red Book of Average Wholesale Prices for Pharmaceuticals. The cost-to-charge ratio for internal medicine was assumed to be 0.50. 1998 price data were used.
Sensitivity analysis A series of one-way sensitivity analyses was performed on all parameters of the model with break-even points being calculated for the most sensitive factors.
Estimated benefits used in the economic analysis The diagnostic accuracy was 84% for the conventional diagnostic strategy versus 94% for the omeprazole test strategy.
Cost results The average cost for the conventional diagnostic strategy was $1,877 versus $1,529 for the omeprazole test strategy.
Synthesis of costs and benefits The average cost per correct diagnosis was calculated as the measure of cost-effectiveness, resulting in values of $1,634 for the omeprazole test strategy versus $2,234 for the traditional diagnostic strategy. The sensitivity analysis established the robustness of the results to changes in the baseline values of the model variables. The break-even points for the prevalence of GERD were 20%, the sensitivity of omeprazole test was 12%, and the cost of omeprazole test was $627.
Authors' conclusions The omeprazole test is sensitive and fairly specific for diagnosing GERD in patients with typical GERD symptoms. This strategy could result in significant cost savings and decreased use of invasive diagnostic tests.
CRD COMMENTARY - Selection of comparators The reason for the choice of the comparator is clear.
Validity of estimate of measure of benefit Although the sample size was relatively small, the estimate of benefits for the omeprazole test strategy is likely to be internally valid given the randomized design adopted. However, for the traditional strategies, the internal validity of the effectiveness estimates cannot be fully assessed given the limited information provided about the literature review and the quality assessment of the primary studies.
Validity of estimate of costs Insufficient details of methods of cost estimation were provided. Quantities of resource use were not reported separately from the costs. The analysis was from the perspective of a third party payer, thus patients' costs were not considered.
Other issues Appropriate comparisons were made with other studies and a comprehensive sensitivity analysis was performed to address the issues of uncertainty in the data. The results may not be generalisable to other settings or countries.
Bibliographic details Fass R, Ofman J J, Gralnek I M, Johnson C, Camargo E, Sampliner R E, Fennerty M B. Clinical and economic assessment of the omeprazole test in patients with symptoms suggestive of gastroesophageal reflux disease. Archives of Internal Medicine 1999; 159: 2161-2168 Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Anti-Ulcer Agents /economics; Arizona; Cost-Benefit Analysis; Cross-Over Studies; Diagnosis, Differential; Double-Blind Method; Esophagus /physiopathology; Female; Gastroesophageal Reflux /diagnosis /economics /physiopathology; Hospitals, Veterans; Humans; Hydrogen-Ion Concentration; Male; Middle Aged; Monitoring, Physiologic; Omeprazole /economics; Predictive Value of Tests; Sensitivity and Specificity AccessionNumber 21999008307 Date bibliographic record published 31/07/2000 Date abstract record published 31/07/2000 |
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