EDITOR, - In her review of hepatitis C Carol A Seymour arrives at a confusing conclusion about the value of liver biopsy in infected asymptomatic blood donors.1 Liver biopsy “seems essential” once the condition has been diagnosed because patients respond to antiviral treatment. Seymour later admits that therapeutic trials are required in this group of patients but then advocates a nationwide policy to identify, follow up, and treat asymptomatic people infected with hepatitis C virus. The two important issues she fails to address are sampling bias in the estimation of the frequency of liver disease in asymptomatic donors and the lack of evidence that treatment affects the long term outlook in hepatitis C.

It is wrong to make statements about the prevalence of disease in selected populations. The careful documentation of the North London Blood Transfusion Centre shows how selected the group who undergo liver biopsy can become.2 In contrast, the investigators in Trent region gave no indication of how many patients did not have a biopsy or what the indications for biopsy were.3 Only studies of unselected or randomly …