What do viral loads mean?
By Tamra B. Orr
Most of us carry around a long list of important numbers in our heads, ready to be pulled out whenever they are needed. We remember our social security numbers, telephone numbers, addresses and zip codes, birth dates and others such as checking account numbers or lock combinations. For patients living with chronic hepatitis B or C, there is another number that joins the ranks: their viral load. It’s a number they usually learn soon after they are diagnosed with the condition, and over the years, although the number typically goes up and down, it remains an important one to remember.
Simply put, a viral load is the amount of virus found in each milliliter (mL) of a person’s blood. “It is reported as copies/mL, or more recently as IU/mL, or international units per milliliter,” explains Dr. Paul Thuluvath, director of the Institute of Digestive Health and Liver Disease at Mercy Medical Center in Baltimore. Converting IU/mL to copies /mL is complicated because several different assays can be used to measure viral load. According to Hepatitis C Support Project’s “HCSP Fact Sheet,” 1 IU can equal between 0.9 copies and 5 copies of the hepatitis C virus, depending on which test was used.
“Most labs give both values, and in the future it may be given only as IU/mL,” says Dr. Philip Rosenthal, medical director of the pediatric liver transplant program at University of California, San Francisco. “Viral load refers to the number of viral particles or amount actually present in the blood or other body fluids. Obviously, the more viral particles present in the blood or fluid, the more likely the virus can be spread to another person.”
The number does not stay constant, however. “It fluctuates and is not considered absolute,” says Dr. Silvia Degli-Esposti, hepatologist and gastroenterologist at the perinatal hepatitis program at the Women and Infants Hospital in Providence, R.I.
One of the first steps following the initial diagnosis of either hepatitis B or C is establishing a beginning viral load. It is typically done through specific blood tests known as quantitative HCV RNA or HBV DNA. This number helps determine what – if anything – is going to happen next.
Knowing the numbers
“Viral load is a measure of the severity of the viral infections,” says Dr. Rosenthal. “The higher the viral load, the more virus that is present and the more chance for the virus to cause harm or injury.”
For those with HBV, knowing the viral load is an essential element in deciding on treatment strategy. An HBV patient’s viral load “could be billions or many millions,” says Dr. Thuluvath. “When it is less than 10,000 IU/mL, the standard practice is not to treat it. We monitor the levels during treatment. Viral loads in HCV could be many thousands or millions.” Treatment for either virus is assessed by a decrease in viral loads; it’s a key to judging overall treatment response – hopefully all the way to where the virus is undetectable.
The viral loads in hepatitis B and C are different. Dr. Ned Snyder, chief of clinical gastroenterology and hepatology at the University of Texas Medical Branch in Galveston, explains, “In hepatitis B, there is a close correlation between the height of the viral load and prognosis. The higher the viral load, the more likely one is to develop cirrhosis or hepatocellular carcinoma (primary liver cancer). Also there are minimal levels of the virus below which treatment in most cases is not necessary.
“On the other hand, the viral load in chronic hepatitis C has nothing to do with prognosis,” Dr. Snyder continues. “There is no correlation between the level of virus and the state of the disease. One may have 100,000 IUs and cirrhosis, and someone with 5 million IUs may have minimal disease. In hepatitis C, the viral load is primarily useful in guiding treatment. The goal of treatment is to make the viral load undetectable and have it remain undetectable after treatment is completed.”
The viral load in hepatitis C has a direct connection to treatment success. Research indicates that for a patient with a high hepatitis C viral load, pegylated interferon and ribavirin are only about 40 percent effective, while those with low viral loads have an effectiveness rate closer to 56 percent. The success of various treatments also depends on other factors including the amount of liver damage already present when the diagnosis is made and how long the person has had the virus, as well as the person’s weight, age and ethnicity.
While liver damage can be significantly influenced by lifestyle choices and diet, the viral load for hepatitis B and C patients is not. “Unfortunately, there is not much patients can do themselves to alter their viral load,” Dr. Snyder says. “Milk thistle and other herbs have not been shown to make a difference.” So although they do not change the viral load, Dr. Rosenthal reminds patients to avoid “medications, herbs or drugs such as alcohol that are known to be hepatotoxic” because they increase the damage being done to the liver.
Other tips
What other information should patients and their families know about viral load? Drs. Rosenthal, Snyder, Thuluvath and Degli-Esposti suggest the following:
For either virus, the higher the viral load, the more likely the virus can be transmitted to another person.
By Tamra B. Orr
Most of us carry around a long list of important numbers in our heads, ready to be pulled out whenever they are needed. We remember our social security numbers, telephone numbers, addresses and zip codes, birth dates and others such as checking account numbers or lock combinations. For patients living with chronic hepatitis B or C, there is another number that joins the ranks: their viral load. It’s a number they usually learn soon after they are diagnosed with the condition, and over the years, although the number typically goes up and down, it remains an important one to remember.
Simply put, a viral load is the amount of virus found in each milliliter (mL) of a person’s blood. “It is reported as copies/mL, or more recently as IU/mL, or international units per milliliter,” explains Dr. Paul Thuluvath, director of the Institute of Digestive Health and Liver Disease at Mercy Medical Center in Baltimore. Converting IU/mL to copies /mL is complicated because several different assays can be used to measure viral load. According to Hepatitis C Support Project’s “HCSP Fact Sheet,” 1 IU can equal between 0.9 copies and 5 copies of the hepatitis C virus, depending on which test was used.
“Most labs give both values, and in the future it may be given only as IU/mL,” says Dr. Philip Rosenthal, medical director of the pediatric liver transplant program at University of California, San Francisco. “Viral load refers to the number of viral particles or amount actually present in the blood or other body fluids. Obviously, the more viral particles present in the blood or fluid, the more likely the virus can be spread to another person.”
The number does not stay constant, however. “It fluctuates and is not considered absolute,” says Dr. Silvia Degli-Esposti, hepatologist and gastroenterologist at the perinatal hepatitis program at the Women and Infants Hospital in Providence, R.I.
One of the first steps following the initial diagnosis of either hepatitis B or C is establishing a beginning viral load. It is typically done through specific blood tests known as quantitative HCV RNA or HBV DNA. This number helps determine what – if anything – is going to happen next.
Knowing the numbers
“Viral load is a measure of the severity of the viral infections,” says Dr. Rosenthal. “The higher the viral load, the more virus that is present and the more chance for the virus to cause harm or injury.”
For those with HBV, knowing the viral load is an essential element in deciding on treatment strategy. An HBV patient’s viral load “could be billions or many millions,” says Dr. Thuluvath. “When it is less than 10,000 IU/mL, the standard practice is not to treat it. We monitor the levels during treatment. Viral loads in HCV could be many thousands or millions.” Treatment for either virus is assessed by a decrease in viral loads; it’s a key to judging overall treatment response – hopefully all the way to where the virus is undetectable.
The viral loads in hepatitis B and C are different. Dr. Ned Snyder, chief of clinical gastroenterology and hepatology at the University of Texas Medical Branch in Galveston, explains, “In hepatitis B, there is a close correlation between the height of the viral load and prognosis. The higher the viral load, the more likely one is to develop cirrhosis or hepatocellular carcinoma (primary liver cancer). Also there are minimal levels of the virus below which treatment in most cases is not necessary.
“On the other hand, the viral load in chronic hepatitis C has nothing to do with prognosis,” Dr. Snyder continues. “There is no correlation between the level of virus and the state of the disease. One may have 100,000 IUs and cirrhosis, and someone with 5 million IUs may have minimal disease. In hepatitis C, the viral load is primarily useful in guiding treatment. The goal of treatment is to make the viral load undetectable and have it remain undetectable after treatment is completed.”
The viral load in hepatitis C has a direct connection to treatment success. Research indicates that for a patient with a high hepatitis C viral load, pegylated interferon and ribavirin are only about 40 percent effective, while those with low viral loads have an effectiveness rate closer to 56 percent. The success of various treatments also depends on other factors including the amount of liver damage already present when the diagnosis is made and how long the person has had the virus, as well as the person’s weight, age and ethnicity.
While liver damage can be significantly influenced by lifestyle choices and diet, the viral load for hepatitis B and C patients is not. “Unfortunately, there is not much patients can do themselves to alter their viral load,” Dr. Snyder says. “Milk thistle and other herbs have not been shown to make a difference.” So although they do not change the viral load, Dr. Rosenthal reminds patients to avoid “medications, herbs or drugs such as alcohol that are known to be hepatotoxic” because they increase the damage being done to the liver.
Other tips
What other information should patients and their families know about viral load? Drs. Rosenthal, Snyder, Thuluvath and Degli-Esposti suggest the following:
For either virus, the higher the viral load, the more likely the virus can be transmitted to another person.
Viral loads should always decrease with appropriate treatment.
It is not useful to monitor hepatitis C viral loads when you are not receiving any treatment.
High viral loads do not necessarily indicate severe disease in hepatitis C.
The HCV RNA or viral load will vary significantly from month to month in patients not receiving interferon/ribavirin, but this does not mean anything.
Do not panic if you hear the viral load is in six or seven figures as this is the usual range with hepatitis C.
In hepatitis B, high viral loads may predispose patients to liver cancer even in the absence of cirrhosis.
In adults with chronic hepatitis B, there is some evidence to suggest that the longer the viral load is high, the more the risk of development of hepatocellular carcinoma.
The field of hepatitis B has changed markedly in recent years, and many generalist physicians are not aware of some of the new concepts and treatments in hepatitis B.
Viral loads can be complicated and confusing for many of us. Dr. Degli-Esposti says, “Explaining viral loads to patients is one of the hardest things I do. They rarely ever understand exactly what I am trying to convey to them.” Instead, our viral load is just one more number we tuck away on our individual internal lists and recall whenever it’s time for a new test. But understanding the significance of that number can help us make informed treatment decisions.
http://www.liverhealthtoday.org/viewarticle.cfm?aid=392
http://www.liverhealthtoday.org/viewarticle.cfm?aid=392
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