9% prevalence of hepatitis C co-infection among UK HIV patients

Just under 9% of HIV-positive individuals in the UK are co-infected with hepatitis C virus, investigators report in the Journal of Viral Hepatitis.

“In comparison with other large cohort studies, the overall HCV [hepatitis C virus] prevalence of 8.9% in the UK…is low,” comment the investigators. They believe that this is because of the low prevalence of HIV among injecting drug users in the UK.

However, approximately 20% of HIV-positive patients in the UK have never been tested for hepatitis C, despite guidance that all patients should be screened annually.

Encouragingly, there was no evidence that co-infection resulted in a poorer response to antiretroviral therapy.

Liver disease caused by hepatitis C is now a major cause of illness and death in HIV-positive patients. However, detailed information on the prevalence of hepatitis C among HIV-positive individuals in the UK is lacking. There is also little information on hepatitis C testing and the impact of co-infection on responses to HIV therapy

Therefore investigators from the UK Collaborative HIV Cohort (UK CHIC) undertook an observational study involving 31,765 patients provided with care at ten specialist HIV clinics between 1996 and 2007. Prevalence of co-infection (determined by a positive hepatitis C antibody result), trends in testing, and responses to HIV therapy were monitored.

Overall, 64% of patients had been tested for hepatitis C at least once. The proportion of patients screened for the virus increased from 9% in 1996 to 80% in 2007.

“There has been a clear instruction that all HIV-positive patients should be screened since at least 2004,” write the investigators. Nevertheless, “20% of patients under follow-up in 2007 had not apparently ever been tested. The latest BHIVA [British HIV Association] guidelines recommend screening all HIV-positive patients at diagnosis, with annual repeat testing in those who are negative.”

Testing rates differed according to HIV risk group, and was highest for gay men (74%), followed by heterosexual men and women (63%). Although injecting drug use is a well-established risk factor for hepatitis C, only 50% of individuals with a history of injecting drug use had been tested for the virus.

However, the investigators think that the true prevalence of testing in this group is likely to be higher. They comment: “these patients may be more likely to have been tested previously.” The researchers also suggest that the higher rates of mortality and loss to follow-up among injecting drug users could also mean this group were less likely to be screened for hepatitis C.

Overall prevalence of hepatitis C was 9%, and prevalence was 8% among those who were receiving care in 2007.

By contrast, prevalence in the general UK population is estimated to be 0.44%. The investigators suggest that the significantly higher prevalence of the infection among patients in the UK CHIC reflects “the shared transmission routes of HCV and HIV.”

Prevalence of hepatitis C differed between HIV risk groups. It was highest in injecting drugs users (84%), followed by gay men (7%), and heterosexual men and women.

However, the investigators suggest that some hepatitis C infections in gay men may actually be due to injecting drug use, who suggest that this behaviour may be “underreported by some MSM [men who have sex with men], sufficient to place them at risk of HCV infection…underreporting of IDU as a risk for HCV transmission in MSM may also affect other cohorts.”

Most co-infected patients were men (80%), white (82%), and their median age was 37. The strongest independent risk factor for co-infection with hepatitis C was HIV transmission group. Injecting drug users were significantly more likely to be co-infected than all other risk groups (p < 0.0001).

The impact of co-infection on responses to antiretroviral therapy was analysed in the 9669 patients who started HIV treatment after 2000. A total of 4% of these patients were co-infected.

Overall, 91% of patients achieved an undetectable viral load. Co-infected patients were just as likely as individuals who were only infected with HIV to achieve this outcome.

There was no association between co-infection and subsequent rebound in viral load. In addition, CD4 cell count increases were comparable between co-infected and HIV-mono-infected patients.

“We found no association between HCV co-infection and either the initial virological response, the rate of viral rebound or the CD4 count response,” emphasise the investigators. They note that results from the Swiss HIV cohort study showed that co-infection did not have an impact on virological responses to therapy.

“The overall cumulative prevalence of HCV of 8.9% in UK CHIC is lower than other cohorts among whom the proportion of IDU is higher,” conclude the researchers. However, they emphasise that this rate of co-infection still “represents a substantial burden of disease.”