I tested positive for hepatitis C antibody after donating blood. My family doctor did a viral load test and that came back negative. I'm not sure what that means. Was my antibody test a false positive? Can this mean that I don't have active virus? I'm confused. I was instructed to go back in six months for another viral load. Any information is greatly appreciated.

D.M.

Hepatitis C is an acute (sudden) or chronic (ongoing) viral infection that can result in serious liver disease, cirrhosis (liver scarring) and death. Most of the acute cases cause no symptoms, and nearly all of the serious manifestations of hepatitis C are due to the chronic form. About 20-30 percent of chronically infected people will develop cirrhosis after 20-30 years. Hepatitis C is acquired through contact with blood or body fluids. It can be transmitted through sex, though this does not occur as often as it does with HIV or hepatitis B.

The standard test for hepatitis C is an antibody test of the blood. This test measures the proteins your body produces to fight the virus. Usually, the first screening test performed is the EIA-2. (EIA stands for enzyme immunoassay, which is the technique used to detect the virus. The EIA-2 is the second-generation form of this test.) It is a sensitive test, detecting more than 95 percent of those with the disease. However, in a setting where those tested are at low risk of actually having hepatitis C, such as blood donors, there can be quite a few false-positive results. If you take a group of patients who are likely to have hepatitis C, such as those with known liver damage and abnormal liver-function tests, then a positive EIA-2 is very likely to represent true infection with hepatitis C.

There are two main methods of confirming a positive hepatitis C antibody test. The first is a different kind of antibody test, called the RIBA (recombinant immunoblot assay). This test is highly accurate, and there are very few false positives. Another confirmatory test involves the detection of the virus itself in the blood. PCR (polymerase chain reaction) is the usual method of detection. This test also measures the quantity of virus in the blood. If the antibody test is positive, and the PCR test is positive, then the patient definitely has hepatitis C. Then, if the patient is treated, the amount of virus can be used to determine how effective the treatment has been.

If the antibody test is positive but the PCR is negative (and that appears to be your case), there are several possibilities. The first is you do not have hepatitis C and your antibody test was falsely positive. To find out, you could have a RIBA test. If that is negative, then you have nothing to worry about at all. Another possibility is that you had an infection with the virus, but your body was able to clear it. Not everyone who gets the virus will have it forever. A final possibility is that you have the infection but the virus is in your blood intermittently. This does not happen very often, but it does happen.

What I would do in your case is test your blood by RIBA. If the result is negative, then you are fine, and you probably never had hepatitis C. If the RIBA is positive, then you will need periodic retesting by PCR. This would prove whether you have the virus in the blood intermittently. If you are repeatedly negative by PCR, then you probably were infected, but you are not now.

One thing you did not mention is your liver function. People with hepatitis C who have repeatedly normal liver-function tests generally have a favorable prognosis. It is generally not recommended that such patients be treated with antihepatitis drugs such as interferon.