Estimated progression rates of Hepatitis C differs according to method of recruitment of study subjects
13 February 2006
Researchers at the MRC Biostatistics Unit in Cambridge have warned of potential bias in the reporting of statistics on the progression of hepatitis C virus (HCV)-related liver disease, which is estimated to affect around 200,000 individuals in England and can result in cirrhosis, liver failure or liver cancer.
Estimates of the rate of progression of hepatitis C-related liver disease are essential for a number of reasons: for predicting the future burden of the infection on health care resources; for predicting individual prognoses; and for use in cost-effectiveness analyses of antiviral therapies. Such estimates are obtained from cohorts of infected patients whose disease stage is measured over time. The Cambridge scientists have now shown that estimated rates of progression vary dramatically between different research study groups, as patients that are recruited into studies may be a select sample. For example, using data from the HCV National Register, the chance of developing cirrhosis after 20 years was estimated to be just 6%. However, data used from a hospital based cohort revealed the chances of developing cirrhosis after 20 years was estimated at 12%. Data from a tertiary referral liver centre revealed the chances being 23%. Importantly, the HCV National Register recruited patients independently of their disease severity, through a ‘lookback’ exercise, which means that subjects were contacted proactively before they presented themselves with illness associated with Hepatitis C virus infection.
Lead author Mr Michael Sweeting of the MRC Biostatistics Unit said, “The significance of this is that researchers using estimates of HCV disease progression should be aware of the source of the cohort of patients that were used to derive the progression rates. Those cohorts derived from tertiary referral centre patients may be showing a much higher progression than is found in the whole infected population.”
