Hepatitis E Virus (HEV)
At a Glance
Hepatitis E is a single-stranded RNA virus spread primarily by fecal-contaminated water in endemic areas but is occasionally person to person, via food or transfusion. Endemic areas include Asia, Africa, the Middle East, and Central America, but the seroprevalence in one U.S. study was 21%. Clinical hepatitis with hepatitis E virus (HEV) is much rarer than this would suggest, and it is unclear whether this seroprevalence is due to a large number of asymptomatic infections, test nonspecificity, or both. The incubation period is 15-60 days.
HEV causes a self-limited acute infection; chronic infections do not occur in normal hosts. Compared with hepatitis A virus (HAV), HEV infections tend to be more severe with potential for prolonged cholestasis in a majority of patients. Jaundice and some combination of malaise, anorexia, nausea, vomiting, abdominal pain, fever, and hepatomegaly are usual.
Fulminant disease occurs more frequently than with HAV, and there is a case-fatality rate of 5-3%. HEV infection in pregnancy is particularly dangerous, with mortality of 15-25% described, as well as poor fetal outcomes.
Chronic HEV has been described in transplant and other immunosupressed patients.
Although no formal guidelines exist for testing, it is reasonable to test patients who recently returned from an endemic area who develop acute hepatitis within 60-90 days of their return. Since there appears to be some domestic transmission of disease in the industrial world as well, patients with acute hepatitis in whom no more-common etiology is identified may also be tested.
What Tests Should I Request to Confirm My Clinical Dx? In addition, what follow-up tests might be useful?
The primary tests available in the United States for HEV are HEV IgM and IgG serologies. HEV RT-PCR testing can be obtained from specialized reference laboratories. HEV IgM may not be positive during initial presentation but becomes positive 1 week to 2 months after onset of illness. HEV IgG appears shortly after the IgM response.
Are There Any Factors That Might Affect the Lab Results? In particular, does your patient take any medications - OTC drugs or Herbals - that might affect the lab results?
No medications are described to interfere with these tests.
Patients' early in infection may have negative serological markers, and antibody development may take weeks to months.
As with many serological tests, false positives occur. An isolated IgM in a patient who never develops an IgG response is most likely a false positive.
Hepatitis E Tests
|Test||Clinical Use and Interpretation|
|Elevated liver indicators; aspartate aminotransferase (AST) alanine aminotransferase (ALT) bilirubins, alkaline phosphatase||Markers of hepatic injury; not specific to HEV but indicate hepatitis is present|
|Hepatitis E IgM||Used for primary diagnosis; positive early in infection, but may not be positive on presentation; declines slowly after acute infection over a period of months|
|Hepatitis E IgG||Becomes positive shortly after HEV IgM; stays positive for years; HEV IgM should turn positive in infected patients with positive HEV IgM|
|Hepatitis E RNA by PCR||Limited availability; usually positive on presentation; virus can be detected in either serum or stool; useful for acute diagnosis in critically-ill patients and for assessment of immunosupressed patients with positive serology and ongoing hepatic disease|
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