The cost-effectiveness of testing for hepatitis C in former injecting drug users.

OBJECTIVES: To evaluate the effectiveness and cost-effectiveness of testing for hepatitis C (HCV) among former injecting drug users (IDUs).

DATA SOURCES: Electronic databases 1996-October 2004. Trent Regional Database Study. Routine UK mortality data.

REVIEW METHODS: A decision analytic model was developed to investigate the impact of case-finding and treatment on progression of HCV disease in a hypothetical cohort of 1000 people. This was compared with a cohort in whom no systematic case-finding is implemented but spontaneous presentation for testing is allowed to occur. A group of epidemiological and clinical experts informed the structure of the model, which has three main components: (1) testing and diagnosis, (2) treatment, and (3) long-term consequences of infection. A fourth component, case-finding strategies, examines the potential impact of case-finding in three settings: prisons, general practice and drug services.

RESULTS: Case-finding for HCV is likely to prevent, for 1000 people approached, three cases of decompensated cirrhosis, three deaths due to HCV and one case of hepatocellular cancer (at 30 years). Twenty-five additional people are likely to undergo combination therapy as a result of initial case-finding. One liver transplant is likely to be prevented for 10,000 people included in case-finding. Case-finding is likely to cost, in the general case, around pounds sterling 760,000 more than a policy of not case-finding. The total cost of either strategy is high and driven predominantly by the cost of treatment with combination therapy (the costs of long-term consequences are heavily discounted owing to the duration of the model). Systematically offering testing to 1000 people would cost around pounds sterling 70,000. In terms of life-years gained, case-finding is likely to result in an additional life-year gained for an investment of pounds sterling 20,084. Taking impacts on quality of life into account gives an estimate for the cost-utility of case-finding as pounds sterling 16,514 per QALY. The probabilistic sensitivity analysis shows that, if NHS policy makers view pounds sterling 30,000 per QALY as an acceptable return on investment, there is a 74% probability that case-finding for HCV would be considered cost-effective. At pounds sterling 20,000 per QALY, the probability that case-finding would be considered cost-effective is 64%. In all analyses, the probability of case-finding being considered cost-effective at a level of pounds sterling 30,000 per QALY was high. Case-finding in drug services is likely to be the most expensive, owing to the high prevalence of cases in the tested population. Correspondingly, benefits are highest for this strategy and cost-effectiveness is similar, in average terms, to the general case. Case-finding in general practice by offering testing to the whole population aged 30-54 years is, paradoxically, estimated to be the least expensive option as only a small number of people accept the offer of testing and HCV prevalence in this group is much higher than would be expected from the general population. Two approaches to case-finding in prison were considered, based on the results of studies in Dartmoor and the Isle of Wight prisons. These differed substantially in the prevalence of cases identified in the tested populations. The analysis based on data from Dartmoor prison had the least favourable average cost-effectiveness of the strategies considered (pounds sterling 20,000 per QALY). Subgroup analyses based on duration of infection show that case-finding is likely to be most cost-effective in people whose infection is more long-standing and who are consequently at greater risk of progression. In people who were infected more than 20 years previously, case-finding yields benefits at around pounds sterling 15,000 per QALY. Treatment effectiveness was modelled using estimates from randomised controlled trials and lower rates of viral response may be seen in practice. However, estimates of cost-effectiveness remained below pounds sterling 30,000 for all levels of treatment effectiveness above 58% of those shown in the relevant trials. The value of information analysis, based on assumptions that 10,000 people might be eligible for case-finding and that programmes would run for 15 years, suggests that the maximum value of further research into case-finding is in excess of pounds sterling 19 million. Partial expected value of perfect information (EVPI) analysis shows that the utility estimates used in the model eclipse all other factors in terms of importance to parameter uncertainty. This is not surprising, since the point estimates for differences in utility between states and across the arms of the model are small.

CONCLUSIONS: Case-finding for hepatitis C is likely to be considered cost-effective by NHS commissioners. Although there remains considerable uncertainty, it appears unlikely that cost-effectiveness would exceed the levels considered acceptable. Further improvements in the effectiveness of treatments to slow or halt disease progression are likely to improve the cost-effectiveness of case-finding. Case-finding is likely to be most cost-effective if targeted at people whose HCV disease is probably more advanced. Further empirical work is required to specify, in practice, different approaches to case-finding in appropriate settings and to evaluate their effectiveness and cost-effectiveness directly.