|
A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer |
Nakama H, Zhang B, Fattah A S |
|
|
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 Three faecal sample collection methods were assessed to clarify the optimum number of times to collect stool specimens for the detection of colorectal cancer. The methods were used to collect samples for use in immunochemical faecal occult tests (Monohaem). The results of the first day of sampling, those of the first and second days, and those of samples taken from 3 consecutive days, were considered as the single-day method (the 2-day method and the 3-day method). In the immunochemical test, Monohaem, for human haemoglobin employed in this study, a high antibody titre with a cut-off point of 0.02 mg/g stool was used.
Economic study type Cost-effectiveness analysis.
Study population Japanese, asymptomatic individuals aged over 40 years of age who participated in a medical check-up for colorectal cancer.
Setting Hospital setting. The economic analysis was carried out in Japan.
Dates to which data relate No dates for the data were given.
Source of effectiveness data The evidence for the final outcomes was based on a single study.
Link between effectiveness and cost data Costing was performed on the same patient sample as that used in the effectiveness analysis. However the authors did not state whether the costing was prospective or retrospective.
Study sample Power calculations were not used to determine the sample size. The study sample consisted of 3,300 asymptomatic individuals who participated in a medical check-up for colorectal cancer.
Study design A prospective cohort study, carried out in a single centre. Patients acted as their own controls as they received all relevant procedures including colonoscopic examinations. The duration of the follow-up appears to have been until the end of the diagnostic procedure. The study appears to have had no loss to follow-up. The six samples of 3 consecutive days' stool from each subject were tested by an immunochemical faecal occult blood, Monohaem, without dietary or medicinal restriction (according to the test principle) before conducting colonoscopy. Faecal smears from the subjects were collected at the laboratory within a day and tested immediately. Meanwhile, all the participants received colonoscopic examinations.
Analysis of effectiveness The principle used in the analysis of effectiveness appears to have been intention to treat. The clinical outcome measures were detection rate and false-positive rate. The number of cancers detected by colonoscopy and the three collection methods were also reported.
Effectiveness results The detection rate and the false-positive rate were calculated as 47% and 3.5% for the single-day method, 82% and 4.7% for the 2-day method and 88 and 5.3% for the 3-day method.
This detection rate was significantly different between the single- and the 2-day methods, as well as between the single- and the 3-day methods (P<0.05).
No significant differences in the false-positive rate were observed between the three testing methods. 17 cancers (0.5%) were detected by colonoscopy. The number of cancers detected for the three collection methods were 8 (0.5%), 14 (0.2%), and 15 (0.5%).
Clinical conclusions A higher positive rate in the faecal occult blood test increases cancer detection, but it also increases false-positive cases detected in the colonoscopic examination. This high positivity rate is a serious limiting factor for wide scale screening of colorectal cancer and reconsideration of the threshold value of this test might be necessary as a trade-off between sensitivity and specificity.
Measure of benefits used in the economic analysis The number of detected cancers reflect the measure of benefits in the economic analysis.
Direct costs Costs were not discounted due to the short time frame of the cost analysis. Quantities were not reported separately from the costs. Cost items were reported separately. Cost analysis covered the costs of faecal occult blood test and colonoscopic examination. The perspective adopted in the cost analysis was not explicitly specified. The source of the cost data appears to have been the study institution. The price year was not specified.
Indirect Costs Indirect costs were not considered.
Currency Japanese Yen (Y). The exchange rate was US$1= Y110 during the period of check-up.
Sensitivity analysis The authors made a brief mention of sensitivity analysis in the text, but no actual sensitivity analysis appears to have been carried out.
Estimated benefits used in the economic analysis 17 cancers were detected by colonoscopy (0.5%). The number of cancers detected for the three collection methods were 8 (0.5%), 14 (0.2%), and 15 (0.5%).
Cost results The total cost for the 3,300 examinees was $29,045.45 for the single-day method, $46,909.09 for the 2-day method, $62,045.45 for the 3-day method.
Synthesis of costs and benefits Average cost per cancer case detected was calculated as the measure of cost-effectiveness, resulting in values of $3,630.68 for the single-day method, $3,350.65 for the 2-day method, and $4,136.36 for the 3-day method. Suggested optimality is based on average cost-effectiveness ratios whereas incremental analysis would not only have been feasible, but also more methodologically sound.
Authors' conclusions This analysis suggests that a 2-day faecal collection method is recommended for immunochemical occult blood screening by Monohaem from the aspects of cost-effectiveness and diagnostic accuracy.
CRD COMMENTARY - Selection of comparators No specific screening method was regarded as the comparator since it was reported that there is no clear understanding on the best number of faecal specimens to be collected to balance an appropriate screening test with optimal cost-effectiveness and a high accuracy. The database user should consider which one of these sampling methods is widely used in their own setting.
Validity of estimate of measure of benefit The effectiveness results are likely to be internally valid given the prospective study design and relatively large sample size, although no power calculations were performed to justify the sample size adopted in this study. The issue of the representativeness of the study sample of the study population cannot be objectively assessed as insufficient information was provided regarding the inclusion and exclusion criteria adopted in the study.
Validity of estimate of costs Quantities were not reported separately from the costs and insufficient details of the methods of cost estimation appears were provided. It was reported that the procedures of this test are uncomplicated and, as a result, the cost analysis was based on cost per slide for each test and the cost of colonoscopic examination for one person. The effects of the three collection methods on indirect costs were not addressed. No statistical analysis was performed on resource use or cost data. The cost results may not be generalisable outside the study setting, as mentioned by the authors.
Other issues The authors' conclusion may not be entirely justified given the lack of extensive sensitivity analysis addressing uncertainties surrounding the costs and clinical outcomes. Although not performing sensitivity analysis was justified by the wide gap in detection rate between the single-day method and the other two methods. The reporting and use of average cost-effectiveness (C-E) ratios is methodologically inferior to incremental C-E ratios. The approach adopted can lead to the decision maker choosing an intervention of lower effectiveness rather than quantifying the additional costs needed to acquire a more effective treatment. The issue of generalisability (regarding the collection methods) to other countries was not addressed. Some comparisons were made with other studies. Based on the studies in the literature, it was concluded that the average costs per case of colorectal cancer detected by the Monohaem method was one-third lower than for the guaiac-impregnated Haemoccult II test. However, it was acknowledged that the cost-effectiveness of immunochemical versus guaiac-based screening can not usually be generalised across different studies and countries as it depends on the technical minutiae of the specific test circumstances. It was acknowledged that despite providing information about the accuracy of a screening test, the present study has limitations compared with a population-based study. However, it was noted that the feasibility of carrying out such a study on a large scale is poor owing to the operational difficulties. Beyond, the above-mentioned note, the issue of the representativeness of the study sample of the study population was not addressed.
Implications of the study To reconfirm the findings of the present study, it would be necessary to conduct a larger population-based prospective study using appropriate methods.
Source of funding Supported in part by Grants-in-Aid for Scientific Research (No 09670384) from the Ministry of Education, Science and Culture of Japan and Cancer Research (No 8-2) from the Ministry of Health and Welfare of Japan.
Bibliographic details Nakama H, Zhang B, Fattah A S. A cost-effective analysis of the optimum number of stool specimens collected for immunochemical occult blood screening for colorectal cancer. European Journal of Cancer 2000; 36(5): 647-650 Indexing Status Subject indexing assigned by NLM MeSH Adult; Aged; Colonoscopy /methods; Colorectal Neoplasms /diagnosis /economics; Cost-Benefit Analysis; False Negative Reactions; False Positive Reactions; Humans; Immunologic Techniques /economics /statistics & Middle Aged; Occult Blood; Sensitivity and Specificity; Specimen Handling; numerical data AccessionNumber 22000000910 Date bibliographic record published 28/02/2001 Date abstract record published 28/02/2001 |
|
|
|