the timing and duration of therapy, and to calculate end of treatment response (ETR) and SVR rate (table 2). Moreover, we assumed that 26% of the subjects who seroconvert would spontaneously clear HCV by the end of the third month, 26% by the end of the fourth month, and 30% by the end of the sixth month.36 Health-related quality of life The quality of life of the HCWs probably deteriorates during the period of waiting for the detection tests to confirm or refute transmission, because of the anxiety generated by the fear of being infected, and was different among different strategies. In addition, in those in whom HCV transmission occurred, life expectancy and health-related quality of life were different when compared with those in whom HCV transmission did not occur. As far as the quality of life of HCWs during the period of waiting for the detection test is concerned, we first assumed that the longer this period was, the more the quality of life will deteriorate. The literature does not include any estimates of the impact of the anxiety generated by the fear of being infected on the quality of life. Rodger et al37 examined the effect of diagnosis of HCV infection on the quality of life of a cohort of patients hospitalised with acute hepatitis 25 years ago. From this study, Thein et al estimated the utilities (ie, recommended health- related quality of life measure) associated with undiagnosed asymptomatic CHC.38 On the basis of these results, the utility we assigned during the month after exposure to HCWs waiting to be informed of their HCV status (ie, with undiagnosed hepatitis C) was 0.86. We assumed that this figure would increase by 0.04 for each month of waiting, and would reach 0.98 at 3 months after HCV exposure. We also assumed that utilities would be higher in HCWs sustaining injuries carrying a low risk of HCV transmission (0.90 at 1 month, 0.94 at month 2 and 0.98 thereafter), and lower in those sustaining injuries carrying a high risk (0.82 at 1 month, 0.86 at month 2, 0.90 at month 3, 0.94 at month 4 and 0.98 thereafter). For HCWs with diagnosed hepatitis C, the utility was assumed to be 0.77. HCWs with a negative HCV RNA test were assigned a utility of 1. Utilities during and after acute hepatitis C treatment with PEG-IFN were based on the study of Thein et al38: 0.82 during the first 2 months, 0.81 during the following 2 months, and 0.79 Table 1 Time to appearance of anti-HCV antibodies, ALT elevation and HCV RNA detection Marker Anti-HCV antibodies ALT HCV RNA Estimates m = 66 days (SD = 28);24 82 days (range, 54–192)25 Model in baseline analysis Normal distribution (m = 66; SD = 28) Median at 46 days;27 1– Exponential 2 weeks before HCV distribution seroconversion28 (l* = 0.015) m = 10 days;24 1– 2 weeks29 Normal distribution (m = 10; SD = 3.5) Models in sensitivity analysis Normal distribution (m = 49; SD = 21) or Normal distribution (m = 82; SD = 28) Exponential distribution (l = 1/ 52) or Exponential distribution (l = 1/ 59) Normal distribution (m = 7; SD = 3.5) or Normal distribution (m = 14; SD = 7) *l is the parameter of the exponential distribution which is equal to ln(2) divided by the median time of elevation of ALT, which was set at 46 days in the base case analysis.27 ALT, alanine transaminase; HCV, hepatitis C virus; m, mean. Gut 2009;58:105–110. doi:10.1136/gut.2007.145516 Hepatology during the last 2 months; utilities attributed to ETR and SVR were 0.80 and 0.87, respectively. Average discounted quality- adjusted life expectancy of a 42-year-old patient with CHC and without CHC (ie, a healthy person) was at 12.44 and 21.77 QALYs, respectively.23 Of note, the latest estimate matched the discounted-adjusted life expectancy of a 42-year-old healthy person in France (ie, 34 undiscounted years) (http://www.who. int/whosis/database/life_tables/life_tables.cfm). Costs The costs of screening tests, outpatient visits, treatment of acute hepatitis C, and treatment and follow-up of CHC for non- responders and relapsers to early treatment in the acute phase were taken into account in this analysis. For screening tests, the following unit costs were obtained from the French Nomenclature des Actes de Biologie M´edicale (Nomenclature of medical biology acts) (available at http://www.ameli.fr/ professionnels-de-sante/directeurs-d-etablissements-de-sante/ index_savoie.php): J18.90 for anti-HCV antibody screening (third-generation ELISA), J5.94 for ALT measurement and J48.60 for HCV RNA detection. We assumed that HCWs attended an outpatient visit at the time of exposure, during follow-up when the HCV RNA was detected, before acute hepatitis C treatment initiation, during treatment (at 1 month, 3 months and at the end of treatment) and 6 months after the end of treatment for ETR and SVR. Doctors’ fees for an outpatient consultation were obtained from the French Nomenclature G´en´erale des actes professionnels (General nomenclature for professional acts) and estimated at J26. Costs of 6 months PEG-IFN therapy for acute hepatitis C were calculated as the average cost of a treatment schedule between PEG-IFN alpha-2a and PEG-IFN alpha-2b (1.5 mg/kg per week): J5841.51. Total discounted lifetime costs of treatment and follow-up of CHC were from the study of San Miguel et al (ie, J26 000, with costs inflated to 2006 Euros.23 Sensitivity analysis First, we considered a low (0.009%) and high (6.669%) risk of HCV transmission after occupational exposure compared with the average of 0.5%. Next, we evaluated the implications of alternative assumptions in areas where we lacked primary data. We varied the distribution of the appearance of anti-HCV antibodies, ALT elevation and HCV RNA detection (table 1). We varied HCWs’ monthly quality of life while waiting for their HCV status over a wide range. We varied the proportion of the subjects who spontaneously clear HCV during the acute phase: between 20 and 30% at month 3 and 4, and between 26 and 35% at month 6. Finally, we varied the discounted cost of treatment and follow-up of CHC between J13 000 and J52 00. Software The model was analysed with TreeAge Pro 2006 software (Williamstown, Massachusetts, USA). RESULTS Baseline analysis Assuming the baseline risk of HCV transmission after a percutaneous injury, table 3 shows for a cohort of 7300 HCWs percutaneously exposed to HCV-positive source patients each year in France and for each studied strategy, the direct medical costs of follow-up, the mean time to HCV diagnosis, the number of patients who developed CHC and the number of CHC cases avoided by early therapy. The highest direct medical 107