Hepatitis A Antibody, IgM (006734) (006734)

Differential diagnosis of hepatitis; the presence of IgM antibody to hepatitis A virus is good evidence for acute hepatitis A.

Hepatitis A virus is a picornavirus, and antibody is made to capsid proteins. Fecal excretion of HAV peaks before symptoms develop. If hepatitis A antibody is IgM, the hepatitis A infection is probably acute. IgM antibody develops within a week of symptom onset, peaks in three months, and is usually gone after six months. Hepatitis A antibody of IgG type is indicative of old infection, is found in almost 50% of adults, and is not usually clinically relevant. Many cases of hepatitis A are subclinical, particularly in children. Presence of IgG antibody to HAV does not exclude acute hepatitis B or other forms of hepatitis.

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