Study type: Blood collected in a gold-, red-, or red/gray-top tube for HAV, HBV, HCV, HDV, or HEV enzyme immunoassay and chemiluminescent immunoassay; related body system: Digestive and Immune systems. Blood collected in lavender-top [EDTA] or white-top [PPT EDTA] tubes for HCV molecular testing of viral DNA or RNA.

Hepatitis is a term used to describe inflammation of the liver. There are a variety of causes of hepatitis that include exposure to hepatotoxic substances such as alcohol or drugs or infection by a hepatitis virus. The resulting illness can range from a mild, self-limiting condition to a life-threatening disease. The disease may present as an acute illness or develop into a chronic condition. This study reviews the viral sources of hepatitis infections.

Vaccination against hepatitis A and hepatitis B can be administered to infants, children, and adults; there is also a combination Hep A/Hep B vaccine for adults. It is not known how long immunization against hepatitis A lasts, but studies have shown it to be effective for at least 10 yr. The hepatitis B vaccine provides lifelong immunity for most people.

HAV:The hepatitis A virus (HAV) is classified as a picornavirus. Its primary mode of transmission is by the fecal-oral route under conditions of poor personal hygiene or inadequate sanitation. The incubation period is about 28 days, with a range of 15 to 50 days. Onset is usually abrupt, with the acute disease lasting about 1 wk. Therapy is supportive, and there is no development of chronic or carrier states. Assays for total (immunoglobulin G [IgG] and immunoglobulin M [IgM]) hepatitis A antibody and IgM-specific hepatitis A antibody assist in differentiating recent infection from prior exposure. If results from the IgM-specific or from both assays are positive, recent infection is suspected. If the IgM-specific test results are negative and the total antibody test results are positive, past infection is indicated. The clinically significant assay—IgM-specific antibody—is often the only test requested. Jaundice occurs in 70% to 80% of adult cases of HAV infection and in 70% of pediatric cases.

HBV:The hepatitis B virus (HBV) is classified as a double-stranded DNA retrovirus of the Hepadnaviridae family. Its primary modes of transmission are parenteral, perinatal, and sexual contact. Serological profiles vary with different scenarios (i.e., asymptomatic infection, acute/resolved infection, coinfection, and chronic carrier state). The formation and detectability of markers is also dose dependent. The following description refers to HBV infection that becomes resolved. The incubation period is generally 6 to 16 wk. The hepatitis B surface antigen (HBsAg) is the first marker to appear after infection. It is detectable 8 to 12 wk after exposure and often precedes symptoms. At about the time liver enzymes fall back to normal levels, the HBsAg titer has fallen to nondetectable levels. If the HBsAg remains detectable after 6 mo, the patient will likely become a chronic carrier who can transmit the virus. Hepatitis Be antigen (HBeAg) appears in the serum 10 to 12 wk after exposure. HBeAg can be found in the serum of patients with acute or chronic HBV infection and is a sign of active viral replication and infectivity. Levels of hepatitis Be antibody (HBeAb) appear about 14 wk after exposure, suggesting resolution of the infection and reduction of the patient’s ability to transmit the disease. The more quickly HBeAg disappears, the shorter the acute phase of the infection. IgM-specific hepatitis B core antibody (HBcAb) appears 6 to 14 wk after exposure to HBsAg and continues to be detectable either until the infection is resolved or over the life span of patients who are in a chronic carrier state. In some cases, HBcAb may be the only detectable marker; hence, its lone appearance has sometimes been referred to as the core window. HBcAb is not an indicator of recovery or immunity; however, it does indicate current or previous infection. Hepatitis B surface antibody (HBsAb) appears 2 to 16 wk after HBsAg disappears. Appearance of HBsAb represents clinical recovery and immunity to the virus.

Onset of HBV infection is usually insidious. Most infected children and half of infected adults are asymptomatic. During the acute phase of infection, symptoms range from mild to severe. Chronicity decreases with age. HBsAg and HBcAb tests are used to screen donated blood before transfusion. HBsAg testing is often part of the routine prenatal screen. Vaccination of infants, children, and young adults is becoming a standard of care and in some cases a requirement.

HCV:The hepatitis C virus (HCV) causes the majority of bloodborne non-A/non-B hepatitis cases. There are six main genotypes, or strains, of the virus, and 50 subtypes of the virus have been identified. It is possible to be infected with more than one genotype at a time. The virus is a flavivirus and contains a single-stranded RNA core. Its primary modes of transmission are parenteral, perinatal, and sexual contact. The incubation period varies widely, from 2 to 52 wk. Onset is insidious, and the risk of chronic liver disease after infection is high. On average, antibodies to hepatitis C are detectable in infected individuals within 4 to 10 wk of infection by enzyme immunoassay screening methods and as early as 2 to 3 wk of infection by PCR methods. Once infected with HCV, 75% to 85% of patients will become chronic carriers. Infected individuals and carriers have a high frequency of chronic liver diseases such as cirrhosis and chronic active hepatitis, and they have a higher risk of developing hepatocellular cancer.

The transmission of hepatitis C by blood transfusion has decreased dramatically since it became part of the routine screening panel for blood donors. The possibility of prenatal transmission exists, especially in the presence of HIV coinfection. Therefore, this test is often included in prenatal testing packages. The test sequence begins with a qualitative immunoassay screening test for viral antibodies. Indeterminate or suspected false-positive results may be confirmed by the RIBA assay, which also detects viral antibodies. NAAT is the method used to document the presence of ongoing infection. Viral genotype testing is used to identify HCV RNA by RT PCR. Hepatitis C antibody testing should not be repeated on a patient who previously tested positive as the antibody will remain present and will therefore provide no clinical benefit; genotype and viral load testing (bDNA or RT PCR) are used to select and guide therapeutic interventions.

Molecular technologies are another approach to testing various specimen types; there are now numerous applications in the areas of pathogen identification (e.g., HCV), disease identification (e.g., oncology), and treatment development. Next-generation sequencing (NGS) is a category of molecular testing used to sequence DNA fragments. NGS technology is capable of sequencing DNA fragments from pathogenic organisms across a range in size from small sequences (single-nucleotide polymorphisms) to large sequences (thousands or billions). Multiplex assays are another type of molecular testing designed to simultaneously sequence DNA fragments from multiple pathogens to help identify mixed populations of infectious agents. The indications for NGS have expanded significantly, and it is now an important tool in the diagnosis/identification of pathogenic organisms. NGS also provides a means and/or the potential to perform prognostic epidemiologic studies, lineage tracing (cell lines), discovery of genetic variants with drug resistance mutations, development of individualized therapeutic regimens, and development of preventive measures (e.g., vaccines).

HDV:Symptoms of hepatitis D virus (HDV) infection are similar but often more severe than those of hepatitis B virus (HBV) infection. As with HBV, the primary modes of HDV transmission are parenteral, perinatal, and sexual contact. The virus contains a single-stranded RNA core. Replication of this virus requires the presence of the hepatitis B outer coat. Therefore, HDV infection can occur only with hepatitis B coinfection or superinfection. Onset is abrupt, after an incubation period of 3 to 13 wk. Because of its dependence on HBV, prevention can be accomplished by using the same pre-exposure and postexposure protective measures used for HBV.

HEV:The hepatitis E virus (HEV) is classified as a single-stranded RNA hepevirus with five separate genotypes. HEV is a major cause of enteric non-A hepatitis worldwide; about 20% of the U.S. population demonstrates presence of IgG antibody. Its primary mode of transmission is the fecal-oral route under conditions of poor personal hygiene or inadequate sanitation. The incubation period is about 28 days. IgM and IgG are detectable within 1 mo after infection. Onset is usually abrupt, with the acute disease lasting several weeks. Therapy is supportive, and patients usually recover, although the disease is quite debilitating during the acute phase. Hepatitis E infection can occasionally develop into a severe liver disease and may cause chronic infection in organ transplant or other immunocompromised patients. Assays for total (IgG and IgM) hepatitis E antibody and IgM-specific hepatitis E antibody help differentiate recent infection from prior exposure. If results from the IgM-specific or from both assays are positive, recent infection is suspected. If the IgM-specific test results are negative and the total antibody test results are positive, past infection is indicated. IgM remains detectable for about 2 mo; IgG levels persist for months to years after recovery.