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Hepatitis E virus (HEV) causes an acute, usually self-limited infection. This small, non-enveloped 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 IgM is the serologic marker of choice for diagnosis of acute HEV infection.
Diagnosis of acute or recent (<6 months) hepatitis E infection
Positive results suggest the presence of acute or recent (in the preceding 6 months) hepatitis E infection. Reflex testing with HEVML / Hepatitis E Virus IgM Antibody Confirmation, Serum will be performed automatically.
Negative results indicate absence of acute or recent hepatitis E infection. If clinical suspicion persists, submit new specimen for retesting in 1 to 2 weeks.
Borderline results may be seen in: 1) acute hepatitis E infection with rising level of anti-hepatitis E virus (HEV) IgM; 2) recent hepatitis E infection with declining level of anti-HEV IgM; or 3) cross-reactivity with nonspecific antibodies (ie, false-positive results). Reflex testing with HEVML / Hepatitis E Virus IgM Antibody Confirmation, Serum will be performed automatically.
Despite having a high specificity rate, the positive predictive value of the hepatitis E virus (HEV) IgM antibody screening test may be low (ie, relatively high frequency of false-positive test results) due to low prevalence of acute hepatitis E in the patient population being screened. HEV IgM antibody confirmatory test would be helpful and necessary to determine the true infection status of patients with reactive HEV IgM antibody screening test results.
A negative test result does not exclude the presence of recent hepatitis E infection, especially in immunocompromised patients. Repeat testing of serum for anti-HEV IgM in 2 to 4 weeks may be necessary for diagnosis of acute in such patients.
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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