Viral Hepatitis (cont.)
What is chronic viral hepatitis?
Patients infected with hepatitis B and hepatitis C can develop chronic
hepatitis. Doctors define chronic hepatitis as hepatitis that lasts longer than
6 months. In chronic hepatitis, the viruses live and multiply in the liver for
years or decades. For unknown reasons, these patients' immune systems are unable to eradicate the
viruses. The viruses cause chronic inflammation of the liver. Chronic hepatitis
can lead to the development over time of extensive liver scarring (cirrhosis),
liver failure, and liver cancer. Liver failure from chronic hepatitis C infection is the
most common reason for liver transplantation in the United States. Patients with
chronic viral hepatitis can transmit the infection to others.
How is viral hepatitis diagnosed?
Diagnosis of viral hepatitis is based on symptoms,
physical findings as well as blood tests for liver enzymes, viral antibodies,
and viral genetic materials.
Symptoms and physical findings
Diagnosis of acute viral hepatitis often is easy, but
diagnosis of chronic hepatitis can be difficult. When a patient reports symptoms
of fatigue, nausea, abdominal pain, darkening of urine, and then develops jaundice, the diagnosis of
acute viral hepatitis is likely and can be confirmed by blood tests. On the
other hand, patients with chronic hepatitis due to hepatitis B and hepatitis C often have no
symptoms or only mild nonspecific symptoms such as chronic fatigue. Typically,
these patients do not have jaundice until the liver damage is far advanced.
Therefore, these patients can remain undiagnosed for years to decades.
Blood tests
There are three types of blood tests for evaluating patients with hepatitis:
liver enzymes, antibodies to the hepatitis viruses, and viral proteins or
genetic material (viral DNA or RNA).
Liver enzymes. Among the most sensitive and widely used blood tests for
evaluating patients with hepatitis are the liver enzymes, called
aminotransferases. They include aspartate aminotransferase (AST or SGOT) and
alanine aminotransferase (ALT or SGPT). These enzymes normally are contained within
liver cells. If the liver is injured (as in viral hepatitis), the liver cells
spill the enzymes into the blood, raising the enzyme levels in the blood
and signaling that the liver is damaged.
The normal range of values for AST is from 5 to 40 units per liter of serum (the liquid
part of the blood). The normal range of values for ALT is from 7 to 56 units per
liter of serum. Patients with acute viral hepatitis (for example, due to
hepatitis A or
hepatitis B) can develop very high AST and ALT levels (sometimes in the thousands of
units per liter range). These high AST and ALT levels will become normal in
several weeks or months as the patients recover completely from their acute
hepatitis. In contrast, patients with chronic hepatitis B and hepatitis C infection
typically have only mildly elevated AST and ALT levels, but these abnormalities
can last years or decades. Since most patients with chronic hepatitis are
asymptomatic (no
jaundice or nausea), their mildly abnormal liver enzymes are
often unexpectedly encountered on routine blood screening tests during yearly
physicals or insurance physicals.
Elevated blood levels of AST and ALT only means that the liver is inflamed, and
elevations can be caused by many agents other than hepatitis viruses, such as
medications, alcohol, bacteria, fungus, etc. In order to prove that a hepatitis
virus is responsible for the elevations, blood must be tested for antibodies to
each of the hepatitis viruses as well as for their genetic material.
Viral antibodies. Antibodies are proteins produced by white blood cells that
attack invaders such as bacteria and viruses. Antibodies against the hepatitis
A, B, and C viruses usually can be detected in the blood within weeks of
infection, and the antibodies remain detectable in the blood for decades
thereafter. Blood tests for the antibodies can be helpful in diagnosing both
acute and chronic viral hepatitis.
In acute viral hepatitis, antibodies not only help to
eradicate the virus, but they also protect the patient from future infections by
the same virus, that is the patient develops immunity. In chronic hepatitis,
however, antibodies and the rest of the immune system are unable to eradicate the virus. The viruses
continue to multiply and are released from the liver cells into the blood where
their presence can be determined by measuring the viral proteins and genetic
material. Therefore in chronic hepatitis, both antibodies to the viruses and
viral proteins and genetic material can be detected in the blood.
Examples of tests for viral antibodies are:
- anti-HAV (hepatitis A antibody)
- antibody to hepatitis B core, an antibody directed against the inner core
(nucleus) of the virus
(core antigen)
- antibody to hepatitis B surface, an antibody directed
against the outer surface envelope of the virus (surface antigen)
- antibody to hepatitis B e, an antibody directed
against the genetic material of the virus (e antigen)
- hepatitis C antibody-antibody against the C virus
Viral proteins and genetic material. Examples of tests for viral proteins and
genetic material are:
- hepatitis B surface antigen
- hepatitis B DNA
- hepatitis B e antigen
- hepatitis C RNA
Other tests. Obstruction of the bile ducts, from either gallstones or cancer,
occasionally can mimic acute viral hepatitis. Ultrasound testing can be used to
exclude the possibility of gallstones or cancer. For more information, please
read the Ultrasound article.
Next: How is viral hepatitis treated? »
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