http://www.labtestsonline.org/understanding/analytes/hepatitis_c/test.html

Each of the five most common tests has a slightly different purpose:

Anti-HCV tests detect the presence of antibodies to the virus,
indicating exposure to HCV. These tests cannot tell if you still have
an active viral infection, only that you were exposed to the virus in
the past. Usually, the test is reported as “positive” or “negative.”
There is some evidence that, if your test is “weakly positive,” it may
not mean that you have been exposed to the HCV virus. The Centers for
Disease Control and Prevention (CDC) revised its guidelines in 2003
and suggests that weakly positive tests be confirmed with the next
test before being reported.

HCV RIBA test is an additional test to confirm the presence of
antibodies to the virus. In most cases, it can tell if the positive
anti-HCV test was due to exposure to HCV (positive RIBA) or represents
a false signal (negative RIBA). In a few cases, the results cannot
answer this question (indeterminate RIBA). Like the anti-HCV test, the
RIBA test cannot tell if you are currently infected, only that you
have been exposed to the virus.

HCV-RNA test identifies whether the virus is in your blood, indicating
that you have an active infection with HCV. In the past, it was
usually performed by a test called a qualitative HCV. Qualitative HCV
RNA is reported as a “positive” or “detected” if any HCV viral RNA is
found; otherwise, the report will be “negative” or “not detected”. The
test may also be used after treatment to see if the virus has been
eliminated from the body.

Viral Load or Quantitative HCV tests measure the number of viral RNA
particles in your blood. Viral load tests are often used before and
during treatment to help determine response to treatment by comparing
the amount of virus before and after treatment (usually after 3
months); successful treatment causes a decrease of 99% or more (2
logs) in viral load soon after starting treatment (as early as 4-12
weeks), and usually leads to viral load being not detected. Some newer
viral load tests can detect very low amounts of viral RNA, and some
laboratories no longer do qualitative HCV RNA tests if they use one of
these versions of viral load testing.

Viral genotyping is used to determine the kind, or genotype, of the
virus present. There are 6 major types of HCV; the most common
(genotype 1) is less likely to respond to treatment than genotypes 2
or 3 and usually requires longer therapy (48 weeks, versus 24 weeks
for genotype 2 or 3). Genotyping is often ordered before treatment is
started to give an idea of the likelihood of success and how long
treatment may be needed.