Wallach's Interpretation of Diagnostic Tests: Pathways to Arriving at a Clinical Diagnosis (182 page)

   Anti-HAV-IgG positive: Remote infection/immune

   Anti-HAV-IgG is usually detectable for life after resolution of acute HAV infection and indicates immunity to HAV infection.

   Anti-HAV-total may be predominantly IgG or IgM, depending on infection status. A negative anti-HAV-total effectively excludes acute HAV but does not distinguish recent from past infection, for which anti-HAV-IgM test is needed. Tests for anti-HAV-total (minimum detection approximately 100 mU/mL) may be insensitive for detection of protective anti-body after HAV vaccine (minimum protective antibody concentration is <10 mU/mL).

   Nonspecific elevation of IgM is common in acute HAV infection.

   
HEV

   HEV infections are caused by an unenveloped, single-stranded RNA virus of the Caliciviridae family and are clinically similar to HAV infections.

   HEV infection is most common in developing countries with inadequate sanitation and limited access to clean water supplies, including countries in Asia, Africa, and Central America; symptomatic infection is rare in the United States and usually occurs in persons with recent travel to an endemic region.

   HEV infections are transmitted by the fecal–oral route. The symptoms of acute HEV infection are similar to those of acute hepatitis caused by other viruses; specific testing is needed to establish HEV infection.

   Asymptomatic infection occurs in approximately 60–90% of patients during outbreaks. Symptomatic infections are most common in young adults (20–40 years); acute liver failure may occur in 1–2% of patients overall but in 10–20% of pregnant women with HEV infection. A cholestatic presentation (duration of infection >3 months), with prolonged jaundice, fatigue, and pruritus, occurs more frequently in HEV infections compared to HAV, but infection eventually resolves completely.

   
HEV diagnosis

   Diagnostic testing is performed by special reference laboratories, like the CDC.

   Anti-HEV-IgM positive: Acute infection.