Newly Developed Immunoassay Evaluated for Infectious Diseases

Although a diagnosis of infectious diseases is essential for timely treatment, the performance of diagnostic tests has been hardly evaluated due to variable results that are influenced by multiple factors in different conditions.

Immunoassays are bioanalytical methods to measure the concentration of an analyte through the reaction of an antigen and an antibody. Most diagnostic tests of infectious diseases are performed in a qualitative manner. By applying a cutoff or ordinal scale to the quantitative results, converted qualitative results reveal discontinuous and reduced information and the result near the cutoff shows high uncertainty.

Medical Laboratory Scientists at Seoul National University Hospital (Seoul, Korea) evaluated the precision, linearity, correlation, and carryover of the analytical performances for the Alinity i by comparison with ARCHITECT i2000SR system (Abbott Laboratories, Abbott Park, IL, USA). For evaluation of compatibility, a total of 800 samples were derived from healthy adults and patients with positive results for various infectious diseases from December 2018 to December 2019.

A total of 16 analytes were selected: HAV Ab IgG(signal/cutoff (S/CO)), HBsAg (S/CO), HBeAg (S/CO), anti‐HBc (S/CO), anti‐HBe (S/CO), anti‐HBs (mIU/mL), anti‐HCV (S/CO), HIV Ag/Ab (S/CO), EBV VCA IgM (S/CO), EBV VCA IgG (S/CO), EBV EBNA IgG (S/CO), CMV IgM (relative light units, RLU), CMV IgG (AU/mL), Toxoplasma IgG (IU/mL), Rubella IgG (IU/mL), and Syphilis TP (S/CO). Among them, anti‐HBs (mIU/mL), CMV IgG (AU/mL), Toxoplasma IgG (IU/mL), and Rubella IgG (IU/mL) are quantitative tests, and the remaining analytes are qualitative tests.

The team reported that for low, medium, and high level of four quantitative analytes (anti‐HBs, CMV IgG, Toxoplasma IgG, and Rubella IgG), the percent coefficient of variation (%CV) of repeatability and intermediate precision were between 0% and 4.18%. For four quantitative analytes (anti‐HBs, CMV IgG, Toxoplasma IgG, and Rubella IgG), all correlation coefficients (r2) for these analytes were ≥ 0.99, representing excellent linearity ranges. In the method comparison between the Alinity i and ARCHITECT i2000SR system, all quantitative analytes showed a very strong correlation (r ≥ 0.994) based on Deming regression. All carryover rate for quantitative and qualitative analytes were less than 1.0% (−0.11% ~ 0.21%).

The authors concluded that the Alinity i system characterized had an excellent performance by ensuring reliable measurements for clinical laboratories and would be suitable as a routine immunoassay analyzer for screening infectious diseases. The study was published on December 7, 2020 in the Journal of Clinical Laboratory Analysis.