hepatic and biliary disorders
Hepatitis B, Acute
Diagnosis of Acute Hepatitis B
Serologic testing In the Initial diagnosis of acute hepatitis , viral hepatitis should be differentiated from other disorders causing jaundice (see figure If acute viral hepatitis is suspected, the following tests are done to screen for hepatitis viruses A, B, and C: IgM antibody to HAV (IgM anti-HAV) Hepatitis B surface antigen (HBsAg) IgM antibody to hepatitis B core (IgM anti-HBc) Antibody to hepatitis C virus (anti-HCV) and hepatitis C RNA (HCV-RNA) polymerase chain reaction If any of the hepatitis B tests are positive, further serologic testing may be necessary to differentiate acute from past or chronic infection (see table Hepatitis B Serology* ). If serology suggests hepatitis B, testing for hepatitis B e antigen (HBeAg) and antibody to hepatitis B e antigen (anti-HBe) is usually done to help determine the prognosis and to guide antiviral therapy. If serologically confirmed HBV infection is severe, antibody to hepatitis D virus (anti-HDV) is measured. Hepatitis B has at least 3 distinct antigen-antibody systems that can be tested: HBsAg Hepatitis B core antibody (HBcAb) HBeAg HBsAgcharacteristically appears during the incubation period, usually 1 to 6 weeks before clinical or biochemical illness develops, and implies infectivity of the blood. It disappears during convalescence. However, HBsAg is occasionally transient. The corresponding protective antibody (anti-HBs) appears weeks or months later, after clinical recovery, and usually persists for life; thus, its detection indicates past HBV infection and relative immunity. In 5 to 10% of patients, HBsAg persists and antibodies do not develop; these patients develop chronic hepatitis B. HBcAbreflects antibody to the viral core. Hepatitis B core antigen (HBcAg) is detectable in infected liver cells but not in serum except by special techniques. Antibody to HBcAg (anti-HBc, or HBcAb) usually appears at the onset of clinical illness; thereafter, titers gradually diminish, usually over years or life. Its presence with anti-HBs indicates recovery from previous HBV infection. Anti-HBc is also present in chronic HBsAg carriers, who do not mount an anti-HBs response. In acute infection, anti-HBc is mainly of the IgM class, whereas in chronic infection, IgG anti-HBc predominates. IgM anti-HBc is a sensitive marker of acute HBV infection and occasionally is the only marker of recent infection, reflecting a window between disappearance of HBsAg and appearance of anti-HBs. HBeAgis a protein derived from the viral core (not to be confused with hepatitis E virus). Present only in HBsAg-positive serum, HBeAg tends to suggest more active viral replication and greater infectivity. In contrast, presence of the corresponding antibody (anti-HBe) suggests lower infectivity. Thus, e antigen markers are more helpful in prognosis than in diagnosis. Chronic liver disease develops more often among patients with HBeAg and less often among patients with anti-HBe. HBV-DNAcan be detected in the serum of patients with active HBV infection. Liver tests are needed if they were not previously done; they include serum alanine aminotransferase (ALT), aspartate aminotransferase (AST), and alkaline phosphatase. Other tests should be done to evaluate liver function; they include serumalbumin, bilirubin, and prothrombin time/international normalized ratio (PT/INR). 