A hepatitis C viral load test measures the amount of virus in a person’s blood. Other tests can confirm an active hepatitis C infection or the virus’s genotype.
Hepatitis C is a viral infection of the liver that can cause short-term (acute) and long-term (chronic) illness.
Acute infections are typically asymptomatic, meaning they have no symptoms. When symptoms do appear, they may
- dark urine or clay-colored stools
- fatigue
- fever
- joint pain
- loss of appetite
- nausea
- vomiting
- yellowing of skin and eyes (jaundice)
According to the World Health Organization, approximately
However, the majority of patients will develop a chronic hepatitis C infection, which is often asymptomatic until liver damage progresses.
A chronic hepatitis C infection can lead to:
- liver damage
- liver cancer
- the need for a liver transplant
Doctors use various tests to learn more about a hepatitis C infection. Some tests can confirm an active infection, others can determine its genotype, and still others can monitor the body’s response to treatment.
This article examines viral load and other hepatitis C tests, including what they measure and how doctors use them.
If your doctor suspects a hepatitis C infection, the first test they typically use is an anti-HCV (hepatitis C antibody test).
A hepatitis C antibody test is a simple blood test used for screening purposes. While this test can detect that the hepatitis C virus (HCV) has been in your bloodstream, it can’t tell the difference between a previously cleared infection and an active one.
In some cases, a weak positive result can be a false positive.
If you test positive for HCV, a doctor will likely follow up with additional testing, such as the qualitative HCV RNA test, to determine if you have an active infection.
A quantitative HCV RNA test can then be done to measure the amount of virus in your blood.
A hepatitis C RNA qualitative test determines whether the hepatitis C virus is present or not present in a blood sample. Results from this test return with either “detected” or “undetected.”
Qualitative hepatitis C testing is more accurate than quantitative testing because it can detect very low levels of the virus in the bloodstream.
The hepatitis C quantitative HCV RNA test measures viral load.
Doctors often use quantitative testing before a person with hepatitis C begins treatment to measure the amount of virus in their bloodstream.
High, low, and undetectable viral loads are as follows:
| Viral load | |
|---|---|
| Low | less than 800,000 international units (IU) per milliliter (mL) |
| High | more than 800,000 IU/mL |
| Undetectable | less than 15 IU per liter (L) |
| Sustained virological response | not detected at least 12 weeks after completing treatment |
Doctors may also use the quantitative HCV RNA test to monitor treatment and guide future treatment decisions.
Your body’s response to treatment is considered positive when the quantitative measurement drops and the virus eventually becomes undetectable.
Can a viral load test determine the severity of liver disease?
Viral load measurements cannot reveal the severity of a person’s liver disease or the degree of scarring (fibrosis). A doctor would need to perform additional testing, such as an ultrasound or CT scan, to check for liver damage.
A hepatitis C genotype is a specific strain of the virus. These are six different hepatitis C genotypes.
A hepatitis C genotype (virus strain) test can reveal which genotype you have and can help determine which medications a doctor will prescribe for your treatment.
Both high and low viral loads require treatment.
After your planned course of treatment is completed, your viral load will be assessed to ensure that viral levels are undetectable.
A viral load of less than 800,000 IU/mL is considered low, while a viral load of over 800,000 IU/mL is considered high. A viral load below 15 IU/L is defined as undetectable.
Meanwhile, a sustained virological response is achieved once hepatitis C is not detected in the blood 12 weeks after completing treatment.
Many people with a high viral load of hepatitis C do not experience symptoms. But when symptoms of hepatitis C do occur, they can include fever, fatigue, stomach pain, loss of appetite, and jaundice.
Viral load tests confirm active hepatitis C infections. It’s not necessary to check the viral load repeatedly during treatment. A doctor will typically check the viral load before treatment and 12 weeks after the completion of treatment.
If a doctor suspects hepatitis C, they’ll typically use a hepatitis C antibody test to confirm whether the virus has been in your bloodstream, followed by a qualitative test to determine if the virus is still active.
A quantitative (viral load test) can then be used to determine how much virus is in your blood stream. Though a viral load test cannot help predict the progression or severity of hepatitis C, it can help guide treatment decisions.
A genotype test may also be used to determine which medications to use for treatment.