The costs of not treating hepatitis C virus infection in injecting drug users in New Zealand.

This paper estimates future health service costs of the current practice in New Zealand of not funding treatment of hepatitis C virus (HCV) infections. Costs are estimated separately for Māori and non-Māori, male and female IDUs. Markov modelling is used to track the infection and progression of HCV to severe liver disease and death, and accumulated costs are estimated for the life of the cohort. Upper and lower estimates of costs are calculated based on different assumptions of the rate of progression of HCV to more severe liver disease. Costs are estimated at dollars 24.6 million per 1000 non-Māori men IDUs (discounted at 3%), under progression assumptions based on liver clinic studies, compared with dollars 10.3 million per 1000 using lower rates of progression based on community studies. Similarly, corresponding costs for non-Māori women are estimated at dollars 27.6 million and $11.2 million per 1000 IDUs. Costs for women are higher because their greater life expectancy is associated with more cases of liver cirrhosis (LC) at older ages. Future costs for Māori are lower than non-Māori, because Māori are more likely to die at younger ages and hence fewer progress to more advanced liver disease. The current situation in New Zealand of not treating HCV infections will result in considerable future costs as some people with HCV progress to more severe liver disease. Provisional estimates are that the accumulated costs of HCV-related liver disease for all IDUs currently infected will be between dollars 166 million at lower rates of disease progression (discounted at 3%) to dollars 400 million at upper rates. Some of the associated morbidity and mortality could have been avoided if the HCV infections had been treated.