Diagnosis

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Hepatitis A

Blood tests are required to diagnose hepatitis A, or HAV. The presence of IgM (anti-HAV antibodies) in the blood confirms that you have an acute infection. After the acute infection resolves, IgG antibodies provide protection from future infections and remain in your blood indefinitely. The vaccine produces anti-HAV IgG antibodies.

Hepatitis B

Many people infected with acute hepatitis B, or HBV, as adults-about 50 percent-have no symptoms, such as jaundice (skin or eyes turning yellow), fatigue, joint pain or malaise. And most infected adults-more than 95 percent-will develop antibodies and clear the infection on their own. Two to 6 percent of adults do not clear the acute infection and develop what is known as chronic infection. They carry the virus and can infect others for the rest of their lives. As many as 1.25 million Americans have chronic HBV infection and can infect others, according to the U.S. Centers for Disease Control and Prevention (CDC).

Acute hepatitis B is diagnosed by detection of IgM antibodies to the hepatitis B core antigen (IgM anti-HBc). HBsAg is positive in both acute and chronic infection. These markers of infection develop in the blood at the time symptoms appear. This can get confusing because testing positive for antibodies doesn't necessarily mean you are infected. Patients who clear hepatitis B have IgG antibodies against hepatitis B core antigen (IgG anti-HBc) and hepatitis B surface antigen (anti-HBsAg) and lack HBsAg. People who have been vaccinated for HBV only test positive for the antibody for surface antigen (anti-HBs). Persistence of HBsAg in the blood over 12 months indicates chronic infection, which can cause serious liver damage over time.

Hepatitis C

Hepatitis C, or HCV, is a virus that takes several forms or genotypes, and it mutates (changes) frequently. There are at least six HCV genotypes (specific strains of the virus) and many subtypes. Approximately 90 percent of patients with acute hepatitis C lack jaundice (yellowing of the eyes and skin), although nearly half will experience nonspecific flu-like symptoms. As liver disease progresses, over 10 to 20 years, those who develop cirrhosis may develop liver-specific symptoms, such as jaundice, itching, dark urine, fluid retention, gastrointestinal bleeding (vomiting blood or blood in the bowel movement), or changes in mood or mental function (encephalopathy). It is uncommon to diagnose HCV in its acute phase; the vast majority of "newly-diagnosed" cases have chronic hepatitis C.

If left untreated, HCV can eventually cause cirrhosis of the liver and liver cancer. About 50 to 85 percent of people infected will develop chronic infection. Those encouraged to seek testing, even if they have no symptoms, include:

• injection drug users, even those with remote past histories

• persons who received blood transfusions or solid organ transplants before 1992

• persons who received clotting factors before 1992 (mostly hemophiliacs)

• dialysis patients

• people with undiagnosed liver problems

• infants born to mothers with HCV (at age 12 to 18 months)

• health care workers exposed on the job

HCV infection is typically suspected if the antibody to HCV is found in a patient with elevated liver enzymes. Active infection is confirmed via detection of HCV RNA, the genetic material of the intact virus, in blood.

In 2001, the U.S. Food and Drug Administration (FDA) granted marketing approval for two polymerase chain reaction (PCR)-based hepatitis C tests. These highly sensitive assays are designed to directly detect the presence of the hepatitis C virus in patients who have evidence of liver disease and antibody evidence of HCV, and are suspected to be actively infected with the virus. Marketed by Roche Diagnostics, the Amplicor HCV Test, version 2.0, and the COBAS Amplicor HCV Test, version 2.0 are the first qualitative nucleic tests to be approved for use in hospitals and licensed laboratories.