Test detects IgM HEV antibody, high titers of IgG anti-HEV, or increasing titers of total HEV antibody by enzyme immunoassays (EIAs) in patients with acute viral hepatitis. The titer of IgM anti-HEV declines rapidly but are detectable for 5 to 6 mths. IgG HEV-antibodies persist and are detected in people without previously recognized hepatitis. To diagnose HEV in these patients, the presence of IgG antibodies should be coupled with the appropriate clinical and epidemiologic presentation.