Cryoglobulinemia: a cause for false negative polymerase chain reaction results in patients with hepatitis C virus positive chronic liver disease

With the introduction of interferon therapy for liver disease due to chronic viral hepatitis, it has become important to test individuals thought to have hepatitis C virus disease for the presence of the virus. Moreover, the current goal of therapy for hepatitis C virus-positive liver disease is to render the individual patient HCV-RNA negative. Recently, it has been reported that as many as one-third of the patients with hepatitis C virus liver disease test positive for the presence of mixed cryoglobulins. Few of these cryoglobulin-positive patients have overt disease manifestations of cryoglobulinemia, such as nephropathy, peripheral neuropathy and vasculitis. Because the cryoglobulins in patients with hepatitis C virus-positive disease are directed at hepatitis C virus epitopes, the precipitation of cryoglobulins from serum samples also effectively removes virus. When the viral carriage rate is low in terms of the number of genomes/unit serum, as occurs in cases that are partially treated, the serum can test negative for hepatitis C virus even by polymerase chain reaction, despite the presence of persistent viremia, if precautions preventing the precipitation of cryoglobulins prior to the removal of the sample for polymerase chain reaction testing are taken. From a group of 75 patients with hepatitis C virus-positive hepatitis seen at our institution in the last year (all HCV-RNA positive), 35% were found to test positive for the presence of cryoglobulins. Importantly, in all cases, the cryoglobulins collected tested strong positive for HCV-RNA. In a minority of cases (20%), with either low levels of HCV-RNA or large amounts of cryoglobulins, with the precipitation and removal of the cryoglobulins, the residual serum tested negative for hepatitis C virus despite utilizing polymerase chain reaction. This suggests that samples being assayed for HCV-RNA should either be collected, taking care to prevent the removal of the HCV-RNA with the cryoglobulins, or alternatively that the cryoglobulins that are collected with the freezing and storage of serum collected from hepatitis C virus-positive patients should be resuspended and assayed for the presence of HCV-RNA.