Health technology Diagnostic tests suitable for screening strategies for hepatitis C. Type of intervention Screening.

Transcription

1 Faut-il depister l'hepatite C: analyse socioeconomique de differentes strategies de depistage de l'hepatite chronique C dans la population francaise [Should hepatitis C be screened: socioeconomic analysis of various screening strategies for chronic hepatitis C in a French population] Rotily M, Loubiere S, Nixon J, Bourliere M, Halfon P, Moatti J P 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 Diagnostic tests suitable for screening strategies for hepatitis C. Type of intervention Screening. Economic study type Cost-effectiveness analysis. Study population Hypothetical male and female asymptomatic patients within the following sub-populations: general population, intravenous drug users (IVDU), haemophiliacs, transfusees and haemodialysis patients. For the general population the age group considered was years. Setting Community and primary care. The economic study was conducted in Marseilles, France. Dates to which data relate The effectiveness data were derived from previous studies conducted between 1993 and Cost data used values but the price year was not given. Source of effectiveness data The effectiveness data were derived from a review of previous studies plus estimates made by cliniciansand hepatogastroenterology practitioners. Modelling A decision tree in Decision Maker was developed to determine the total cost, effectiveness (measured in the number of true cases detected (base-case solution)) and a modified effectiveness which adjusted for false positive and false negative results (modified solution), and cost-effectiveness ratio. Outcomes assessed in the review The outcomes assessed in the review were the sensitivity and specificity of each of the diagnostic tests and the seroprevalence of hepatitis in the five populations studied. These wereutilised in determining the probabilities of events Page: 1 / 6

2 occurring in the decision tree. Study designs and other criteria for inclusion in the review Sources searched to identify primary studies 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 6 primary studies were included. Methods of combining primary studies Primary studies were combined using a narrative method based on clinical interpretations for some test parameters (e.g. ALAT). Investigation of differences between primary studies Not undertaken. Results of the review The sensitivity and specificity for each test was: ALT 60% and 80%; ELISA99% and 90%; RIBA 98% and 95%; PCR 99.9% and 99.3%. The prevalence for each population was: general population 1.2%; IVDU 80%; transfusees 7%; haemophiliacs 66%; haemodialysis patients 20%. Page: 2 / 6

3 Measure of benefits used in the economic analysis The measure of benefit as determined by the model was the number of true positive cases (TP) detected. A modified measure of effectiveness was also determined which moderated the benefit results by weighting false positives and false negatives differently from true positives (1) and true negatives (0). Direct costs Direct costs included the cost of a consultation with a GP and the costs of analysing the test results for each screening strategy. The method used to calculate each item was based on the reimbursement rates as defined by the social insurance companies in France. The boundary adopted was therefore the third party payer. Costs and quantities were reported separately but discounting was not considered. Statistical analysis of costs Not undertaken. Indirect Costs Not considered. Currency French Francs (FF). Sensitivity analysis Although the authors indicated that sensitivity analyses were conducted they were not reported other than the modified solution which ascribed values other than 0 to negative results. The specific values given were -1 for a false negative and for a false positive. Estimated benefits used in the economic analysis The number of cases detected (true positives) for the IVDU population (as an example sub population) was: PCR = 89,910; PCR, PCR = 89,820; ELISA = 89,100; ELISA, PCR = 89,610; ELISA, ELISA = 88,209, ELISA, RIBA = 87,318; ELISA+ELISA (parallel testing) = 89,820; ELISA, RIBA, PCR = 89,098; ALAT = 54,000; ALAT, ELISA = 53,460; ALAT, PCR = 53,946. Page: 3 / 6

4 Details for the general population were also provided but are not reported here. Cost results The total cost in millions of Francs for screening the IVDU population (as an example) for each strategy would be: PCR = 120; PCR, PCR = 183.2; ELISA = 57.5; ELISA, PCR = 124.1; ELISA, ELISA = 74.8; ELISA, RIBA = 88.2; ELISA+ELISA (parallel testing) = 84.9; ELISA, RIBA, PCR = 93.5; ALAT = 36.7; ALAT, ELISA = 48.8; ALAT, PCR = Costs for the general population were also given but are not reported here. Synthesis of costs and benefits Cost per true case detected was reported. The base-case solution results showed that for all populations screened a single ELISA test produced the most favourable cost-effectiveness ratio (average cost per case detected). Using the IVDU population as an example the results were: PCR = 1,334; PCR, PCR = 2,040; ELISA = 645; ELISA, PCR = 1,393; ELISA, ELISA = 848; ELISA, RIBA = 1.011; ELISA+ELISA (parallel testing) = 945; ELISA, RIBA, PCR = 1,049; ALAT = 680; ALAT, ELISA = 913; Page: 4 / 6

5 ALAT, PCR = 1,537. The modified solution produced the same results with the exception that the ELISA, RIBA strategy was shown to be the most cost-effective for the general population. Authors' conclusions The authors concluded that a single ELISA test would produce the most cost-effective screening solution for testing all populations considered but that a confirmation test (using for example a PCR) would be necessary to reduce the number of false results. This, however, would reduce the cost-effectiveness ratio. The natural history of the disease in relation to the seroconversion period (during which time anti-bodies to the hepatitis C virus are not detectable by anything other than a PCR test) accounts for the increased number of false negative results in other diagnostic tests. The modified solution takes into account the negative impacts of false negatives and false positives and confirms the chosen strategy for all populations except the general population. Further research is, however, necessary to extend the boundary of the screening analysis in order to provide a cost-benefit analysis of the screening versus no screening options by taking into account all subsequent diagnostic and treatment costs. Benefit measures which consider quality of life for the patients are needed in order to achieve this extended analysis. CRD COMMENTARY - Selection of comparators The reason for the choice of comparators is clear. All strategies utilised were derived from clinicians and diagnosticians in the field of hepatology and include standard diagnostic tests in the diagnosis of hepatitis C. Validity of estimate of measure of benefit The estimate of benefit is likely to be valid (true cases detected). The modified solution, however,represented a measure which would be difficult to classify (such as the number of modified true cases detected) and therefore, even though based on accepted methodology in cost-effectiveness analysis, it creates some difficulties in interpretation. A full sensitivity analysis would have supported the robustness of the solution as some estimates of effectiveness (especially for the ALAT test) had a degree of uncertainty attached to them. Validity of estimate of costs The estimate of costs is likely to be valid as it was based on reimbursement figures from the French Government although again, no statistical analysis or sensitivity analysis of costs was reported. Other issues The authors acknowledged that the present study limits its analysis to the examination of potential screening strategies but that the boundary of analysis needs to be extended to fully cost the consequences of screening in terms of diagnosis and treatment. In addition the benefits brought to patients in terms of life years gained or a quality of life gained from screening need to be addressed in order to complete the analysis. ALAT = ALT (English abbreviation). Implications of the study The present study identifies the need to consider the policy of screening, particularly in high risk populations such as IVDU. Further research is needed, however, to extend the cost and benefit analysis and to consider how implementation might be achieved should a policy to screen be adopted by the French Government. Source of funding None stated. Bibliographic details Page: 5 / 6

6 Powered by TCPDF ( Rotily M, Loubiere S, Nixon J, Bourliere M, Halfon P, Moatti J P. Faut-il depister l'hepatite C: analyse socioeconomique de differentes strategies de depistage de l'hepatite chronique C dans la population francaise. [Should hepatitis C be screened: socioeconomic analysis of various screening strategies for chronic hepatitis C in a French population] Gastroenterologie Clinique et Biologique 1997; 21(1 Part 2): S33-S40 PubMedID Indexing Status Subject indexing assigned by NLM MeSH Alanine Transaminase /blood; Chronic Disease; Cost-Benefit Analysis; Decision Support Techniques; Decision Trees; Enzyme-Linked Immunosorbent Assay; France; Hepatitis C /economics /prevention & control; Humans; Immunoblotting; Mass Screening /economics /methods; Polymerase Chain Reaction; Sensitivity and Specificity; Socioeconomic Factors AccessionNumber Date bibliographic record published 30/11/1998 Date abstract record published 30/11/1998 Page: 6 / 6