Hepatitis B Virus Surface Antigen (HBsAg) EIA

The Alinity s HBsAg assay is a chemiluminescent microparticle immunoassay (CMIA) used for the qualitative detection of hepatitis B surface antigen (HBsAg) in human serum and plasma specimens on the Alinity s System.

The Alinity s HBsAg assay is intended to screen individual human donors, including volunteer donors of whole blood and blood components, and other living donors for the presence of HBsAg. The assay is also intended for use in testing serum and plasma specimens to screen organ donors when specimens are obtained while the donor’s heart is still beating, and in testing serum specimens to screen cadaveric (non-heart-beating) donors. It is not intended for use on cord blood specimens.

About Hepatitis B Surface Antigen

Hepatitis B virus (HBV) is the causative agent of hepatitis B. An estimated 257 million individuals are living with hepatitis B virus infection. More than 887 000 people die annually of HBV-related liver disease. Globally, chronic hepatitis B is a major cause of liver cirrhosis and hepatocellular carcinoma.^{1, 2} HBV belongs to the hepadnavirus family and is a partially double-stranded DNA virus. It consists of a central core nucleocapsid containing viral DNA, DNA polymerase, and a surrounding envelope consisting of HBsAg, which is expressed during HBV infection. Additionally, HBV-infected cells produce spherical or long filamentous particles that consist of excess HBsAg.³ The virus is divided into multiple major serotypes (e.g., adr, adw, ayr, ayw) based on antigenic determinants present on the envelope proteins, and into at least 8 genotypes (A–H) according to overall nucleotide sequence variation of the genome.

Differences among genotypes can affect the disease severity, course and likelihood of complications, response to treatment, and possibly vaccine protection.^2-5

HBV, unlike other DNA viruses, replicates through a reverse transcription step. The reverse transcription process lacks proofreading capability; therefore, HBV is subject to a mutation rate more than 10 times higher than the mutation rate of other DNA viruses. Surface antigen gene mutations may cause changes in the antigenic structure of HBsAg, resulting in reduced recognition by some antibodies to HBsAg.^6-11 HBV is transmitted through sexual, parenteral, and perinatal routes. Transmission may also occur through transfusion of HBV contaminated blood and blood products. After infection with HBV,

HBsAg is the first antigenic marker, appearing 1 to 12 weeks after exposure and 2 to 6 weeks before the onset of clinical symptoms. HBsAg persists during this acute phase and clears late in the convalescence period. Failure to clear HBsAg within 6 months indicates a chronic hepatitis B infection.^{2, 3}

This assay is for the qualitative detection of HBsAg in human serum and plasma using chemiluminescent microparticle immunoassay (CMIA) technology.

Sample, anti-HBs coated paramagnetic microparticles, and anti-HBs acridinium-labeled conjugate are combined to create a reaction mixture and incubated. The HBsAg present in the sample binds to the anti-HBs coated microparticles and to the anti-HBs acridinium labeled conjugate. The mixture is washed. Ancillary wash buffer is added and incubated. Following a wash cycle, Pre-Trigger and Trigger Solutions are added. The resulting chemiluminescent reaction is measured as relative light units (RLU). There is a direct relationship between the amount of HBsAg in the sample and the RLU detected by the system optics.

The presence or absence of HBsAg in the sample is determined by comparing the chemiluminescent RLU in the reaction to the cutoff RLU determined from an active calibration.

Test performed by Eurofins DPT, 6933 S. Revere Parkway, Centennial, CO 80112.

This test has been cleared or approved for diagnostic use by the U.S. Food and Drug Administration. See package insert for more information.