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Diagnosis of past exposure to hepatitis E virus
See Testing Algorithm for the Diagnosis of Hepatitis E in Special Instructions.
Hepatitis E virus (HEV) causes an acute, usually self-limited infection. This small, nonenveloped RNA virus is from animal reservoir (eg, hogs) to humans via the fecal-oral route. HEV is endemic in Southeast and Central Asia, with several outbreaks observed in the Middle East, northern and western parts of Africa, and Mexico. In developed countries, HEV infection occurs mainly in persons who have traveled to disease-endemic areas. Transmission of HEV may also occur parenterally, and direct person-to-person transmission is rare. Clinically severe cases occur in young to middle-aged adults. Unusually high mortality (approximately 20%) occurs in patients infected during the third trimester of pregnancy. Although there is no carrier state associated with HEV, immunocompromised patients may have prolonged periods (eg, months) of viremia and virus shedding in the stool.
In immunocompetent patients, viremia and virus shedding in the stool occur in the pre-icteric phase, lasting up to 10 days into the clinical phase. After an incubation period ranging from 15 to 60 days, HEV-infected patients develop symptoms of hepatitis with appearance of anti-HEV IgM antibody in serum, followed by detectable anti-HEV IgG within a few days. Anti-HEV IgM may remain detectable up to 6 months after onset of symptoms, while anti-HEV IgG usually persists for many years after infection. Anti-HEV IgG is the serologic test of choice to determine past exposure to HEV.
Positive results indicate past or resolved hepatitis E infection.
Negative results indicate absence of previous exposure to hepatitis E virus (HEV).
Borderline results may be seen in: 1) acute or recent hepatitis E infection with rising level of anti-HEV IgG, or 2) cross-reactivity with nonspecific antibodies (ie, false-positive results). Repeat testing of serum for anti-HEV IgG in 4 to 6 weeks is recommended to determine the definitive HEV infection status.
A negative test result does not exclude the presence of recent hepatitis E infection (<2 month duration), especially in immunocompromised patients. Repeat testing for anti-hepatitis E virus (HEV) IgM and anti-HEV IgG in 1 to 2 months is necessary for diagnosis of recent hepatitis E.
Performance characteristics of this assay have not been established for serum specimens that are icteric, lipemic, hemolyzed, or contain particulate matter.
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