Axsym microparticle enzyme immunoassay

HBV DNA levels were measured with quantitative PCR assay (PG Company, Shenzhen, China). The test detection range is 500 to 1.0 × 10⁹ IU/mL. HBsAg was quantified using the Architect platform (Abbott Laboratories, Chicago, IL) per the manufacturer's instructions, and it was calibrated using the WHO standard for HBsAg. HBeAg levels were measured using the AxSYM microparticle enzyme immunoassay (Abbott). The AxSYM assay measures the ratio of the sample (S) to the cut-off (Co) (S/Co ratio), and an S/Co ratio ≥1.0 is defined as HBeAg-positive. Detection of HBV genotypes was performed as previously described.^{15 (link)} Other serum biochemical parameters were determined using a biochemistry analyzer within 1 week prior to liver biopsy.

We identified records through Territory Pathology (Northern Territory public pathology laboratory), which covers all Northern Territory Government health care facilities including correctional facilities. All serological testing was performed at a single central lab located at Royal Darwin Hospital. Records of testing for hepatitis B and hepatitis C serology between 2003 and 2017 were generated by the pathology information system by searching for all results in which the location of testing was specified to a correctional facility in the Northern Territory. Serology for hepatitis B and hepatitis C was performed using Abbot AxSYM™ Microparticle Enzyme Immunoassay between 2003 and May 2007, and the Abbot Architect i2000SR-Chemiluminescent Microparticle Immunoassay between May 2007 and 2017. Hepatitis B and hepatitis C viral loads are performed in another state, and we did not have access to this data. Most serological testing was performed at another pathology provider (other than Territory Pathology) between 2007 and 2010 and we did not have access to the results from this provider.

Anti-CD3, anti-CD4, and anti-perforin monoclonal antibodies were purchased from Becton Dickinson (Franklin Lakes, NJ). Anti-CD28 monoclonal antibodies were purchased from Beckman Coulter (Fullerton, CA). The simultaneous presence of CD3, CD4, CD28, and perforin was evaluated on peripheral blood mononuclear cells using four-color flow cytometry (FACSCalibur, BD) and analyzed using the CellQuest software (BD). The cut-off value for percentage of CD4⁺CD28^null cells in our lab is established at 5%. In addition, we tested the presence of CD25 and killer cell immunoglobulin-like receptors (KIR2DS1 and KIR2DS2) (BD).
Antibodies against hHSP60 were determined as described previously [21 (link)]. Results are expressed as anti-hHSP60 levels in arbitrary units (AU)/mL. The cut-off value for this test was previously established at 80 AU/mL [21 (link)].
Anti-CMV antibodies were determined using the axSYM microparticle enzyme immunoassay (Abbott Laboratories, Abbott Park, IL). Results are expressed as anti-CMV levels in AU/mL. The cut-off value for this test is 15 AU/mL.