Recombinant ImmunoBlot Assay (RIBA) Test for HCV

The Recombinant ImmunoBlot Assay (RIBA) is a blood test that detects antibodies to the hepatitis C virus (HCV). It was used for many years as a secondary confirmation test if a first-line screening test for HCV (called the ELISA hepatitis C antibody test) came back positive or indeterminant. 

As other tests became more sensitive and accurate, this test was discontinued for detecting HCV and other tests are now used instead. However, if you've had it in the past and see it in your medical chart, you might want to know what your results mean.

How the Test Works

When you have been exposed to hepatitis C, your body's immune system makes antibodies to fight the virus. These antibodies circulate in your bloodstream for many years, even after the infection resolves—perhaps even throughout your lifetime. The RIBA HCV test was used to detect those antibodies.

Who Is Tested?

The hepatitis C virus is spread through direct contact with infected blood, and testing is recommended for people who are at risk of having the infection.

Pregnant women are generally tested for this virus. People who have HIV or who have received an organ transplant may need testing as well.

Routine periodic testing is recommended for people who currently inject drugs and share needles, syringes, or other drug preparation equipment and people who have certain medical conditions, including ever having received maintenance hemodialysis.

Your blood will also be tested if you donate blood because blood transfusions can transmit the hepatitis C virus to the recipient if the virus is present in the donor blood. If you submit donor blood that tests positive for HCV antibodies, it will be rejected and you will be permanently not eligible to donate blood in order to protect people who receive blood transfusions.

Use of the RIBA HCV Test

If you are looking at older laboratory results in your medical record, you may see the Hepatitis C RIBA test reported. It may be called "HCV RIBA" or it may be spelled out as "Recombinant ImmunoBlot Assay." It would have been ordered if your original ELISA screening test for the hepatitis C antibody (anti-HCV) was either positive or indeterminant.

In past years, the first ELISA tests that were performed to look for the hepatitis C antibody often had false positives, meaning that they showed a positive result when you actually didn't have any hepatitis C antibody. As a result, it was necessary to double-check every positive result with a second, confirmatory test.

The RIBA HCV test is less likely to be falsely read as positive than the ELISA hepatitis C antibody test. But it's also an additional expense, so it was performed only if the ELISA anti-HCV test showed a positive result.

Positive and Negative Results

After a RIBA HCV test, the next steps in your testing would have depended on whether this confirmatory test was positive or negative.

Positive RIBA

If the RIBA HCV test also showed a positive result, this confirmed that you had hepatitis C antibodies and had been exposed to HCV. The next step was to test for HCV RNA (viral load) to see if the hepatitis C virus was still present in your body.

Negative RIBA

If the RIBA test came back negative, your healthcare provider may have ordered other tests to ensure that you didn't have HCV, depending on whether you were showing signs of the disease or you had a condition that might affect the accuracy of the tests

Recombinant ImmunoBlot Assay Testing Discontinued

The Centers for Disease Control and Prevention notes that the RIBA HCV test has been discontinued. The manufacturer, Novartis Vaccines, and Diagnostics, no longer offers it for use. Instead of using RIBA as the confirmatory test, clinicians now use a test that detects HCV viremia (the presence of HCV in the blood) and viral load.