Hepatitis C diagnosis and treatment, impact on engagement and behaviour of people who inject drugs, a service evaluation, the hooked C project.

There is emerging evidence that Hepatitis C (HCV) treatment engagement is associated with change in drug behaviours and reduced drug-related death rates among people who inject drugs (PWID). The project aims to investigate whether HCV diagnosis and treatment engagement reduces all-cause mortality and drug-related death, and whether any effect is dependent on treatment regimen and intensity of engagement with staff. Case-control studies comparing: PWID with active HCV infection (PCR positive) to PWID HCV infected but spontaneously resolved (PCR negative); PCR-positive patients who engaged with treatment services to nonengagers; and patients who received interferon vs direct-acting antiviral (DAA) based treatment. No differences in risk of all-cause mortality or drug-related death between PCR-negative controls and PCR-positive cases were detected. The odds of all-cause mortality was 12.2 times higher in nonengaging persons compared to treatment engaging cases (aOR 12.15, 95% CI 7.03-20.99, P < .001). The odds of a drug-related death were 5.5 times higher in nonengaging persons compared with treatment engaging cases (aOR 5.52, 95% CI 2.67- 11.44, P < .001). No differences in risk of all-cause mortality or drug-related death between interferon-treated cases and DAA-treated controls were detected. HCV treatment engagement is significantly protective against all-cause mortality and drug-related death. This engagement effect is independent of treatment regimen, with the introduction of DAA therapies not increasing risk of drug-related death, suggesting intensity of HCV therapy provider interaction is not an important factor.