HEPATITIS BE VIRUS ANTIGEN

Code
000.0000
Name
HEPATITIS BE VIRUS ANTIGEN
Category
None
Department
Send-Out
Start Date
Expiration Date
Synonyms
HEP BE AG
CPT Codes
87350
Site
SBMF
Reference Test
44080
ATLAS Test Code

Specimen Information

Type

Gold, SST

Volume

1.0 ml

Transport Info

Centrifuge and immediately transfer serum to separate plastic tube
Refrigerated

Fasting Required?
False
Patient Instructions

Reference Range

Negative

Methodology

Enzyme Immunoassay (EIA)

Clinical Significance

Diagnosis and monitoring of both acute and chronic infections due to hepatitis B virus.

The laboratory diagnosis and monitoring of both acute and chronic infections due to hepatitis B virus (HBV) involves the use of several of the following tests: hepatitis B surface antigen (HBsAg), the e antigen (HBeAg), antibody to the core antigen (anti-HBc), antibody to the e antigen (anti-HBe), and antibody to the surface antigen (anti-HBs). Immunity conferred by the HBV vaccine can also be assessed by measuring levels of anti-HBs (although the CDC does not recommend post-vaccination testing). Groups of HBV tests are recommended for the following clinical situations: (1) suspected acute viral hepatitis, HBsAg, IgM anti-HBc; (2) chronic hepatitis, HBsAg, anti-HBc, and anti-HBs; and (3) monitoring chronic HBV infection, HBsAg, HBeAg, anti-HBs, anti-HBe, and quantitative or qualitative HBV DNA. The result pattern of these tests are particularly helpful in differentiating acute hepatitis, chronic hepatitis, and the chronic carrier state. The pattern of reactivity is reflective of the natural course of infection. HBsAg usually becomes detectable 2 weeks to 2 months before clinical symptoms, and as little as 2 weeks after infection. It is usually present for 2 to 3 months. Five to 10 percent of patients will have persistent HBsAg levels beyond 6 months (chronic carrier, chronic hepatitis). The EIA test will detect 100 pg/mL or more of HBsAg. All positive HBsAg are further tested using the HBsAg confirmation test. About 5% of positive HBsAgs are false positives and will not neutralize in the confirmatory assay. Anti-HBc IgM first becomes detectable at about the same time as clinical symptoms appear and serum transaminases rise. It will usually persist for several months and occasionally up to a year. Anti-HBc IgG appears soon after IgM and will persist for years, ultimately disappearing in some patients. IgM may be present in cases of chronic hepatitis. The appearance of anti-HBs usually follows the disappearance of HBsAg. It persists for years and is associated with relative or absolute immunity. In patients who have received the HBV vaccine, this antibody should be the only one to appear in responders. Response depends strongly on age, sex, obesity, and general health. About 95% of healthy, thin women in their 20's will develop antibodies after a three-dose course. Twenty-five to 50 percent of non-responders will ultimately seroconvert after a repeat course. Assessing responsiveness in vaccinees is only recommended in selected subgroups (e.g., those with high prevalence of infection or health care workers). Levels less than 10 IU/L are considered negative and non-protective. The HBeAg appears in close association with HBsAg, but normally does not persist as long. Its presence is generally associated with higher infectivity, but it is of limited usefulness diagnostically. The development of anti-HBe coincides with the disappearance of e antigen. This is usually after the appearance of anti-HBc and before that of anti-HBs. Anti-HBe often disappears, but its persistence has been associated with chronic hepatitis and the chronic carrier state. It does not confer protection. The typical case of acute HBV hepatitis will be characterized by the presence of HBsAg and anti-HBc IgM. The latter is particularly helpful in HBsAg-negative cases. It is not recommended to rely solely on surface antigen determinations for diagnosing acute infection. In the antigen-negative cases, the presence of IgM and total anti-HBc and the presence of HBV DNA, in the absence of anti-HBs, will help to confirm the acute case. In chronic hepatitis, HBsAg will be present together with anti-HBc, but without anti-HBs. HBeAg may or may not be present. The newest tests in the assessment of HBV infections are the qualitative and quantitative measures of HBV DNA by molecular methods (PCR or probe or both). In the qualitative assay, a highly conserved region of the surface gene of HBV is detected at a level as low as 200 copies of the viral genome per mL. This assay may be of use in confirming infection in patients with equivocal HBsAg results. The quantitative test employs an RNA probe and has a detection limit of 0.02 pg/mL or 5,000 copies/mL, making it less sensitive than the qualitative assay. It is useful in monitoring therapeutic responsiveness in chronically infected patients. Approximately 1% of blood donors will have a positive anti-HBc and negative HBsAg. These donors should be further evaluated by measuring anti-HBs. Most of these donors will have a negative anti-HBs (see Draelos, et al.). Vaccinating donors with this pattern of results showed that the anti-HBc was a cross-reacting antibody.

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