Related Experiment Video
Updated: May 15, 2026
A Multiplex Serological Assay for the Detection of Antibody Responses to Arboviruses
Published on: November 4, 2025
Investigation into low-level anti-rubella virus IgG results reported by commercial immunoassays
Wayne Dimech1, Nilukshi Arachchi, Jingjing Cai
1NRL, Melbourne Australia, Victoria, Australia. wayne@nrl.gov.au
Insights
Commercial anti-rubella virus IgG assays show poor standardization despite calibration against a WHO standard. This study reveals significant variability in results, questioning the relevance of current quantification methods for rubella virus IgG.
Area of Science:
- Immunology
- Virology
- Clinical Diagnostics
Background:
- Commercial anti-rubella virus IgG assays have been calibrated to a WHO International Standard since the 1980s, with results reported in IU/ml.
- Despite this standardization effort, concerns exist regarding the consistency and comparability of results across different commercial immunoassays (CIAs).
Purpose of the Study:
- To evaluate the concordance and correlation of quantitative results from multiple commercial anti-rubella virus IgG immunoassays (CIAs).
- To assess the diagnostic performance (sensitivity and specificity) of CIAs compared to a reference standard.
- To investigate the impact of long-term calibration on the standardization of rubella virus IgG quantification.
Main Methods:
- Five different commercial immunoassays (CIAs) were used to test 100 patient samples each, yielding 500 quantitative results.
- Results were compared against an in-house enzyme immunoassay (IH-EIA) calibrated with the WHO standard.
- Samples were also screened using hemagglutination inhibition assay (HAI) and immunoblot (IB) assays to establish a reference negative/positive status.
Main Results:
- Concordance between CIA qualitative results and the assigned status varied significantly, ranging from 50.0% to 97.8%.
- Receiver operating characteristic analysis showed estimated sensitivity and specificity ranging from 70.2% to 100%.
- Poor correlation (R(2) from 0.002 to 0.413) was observed between quantitative CIA results and the IH-EIA, indicating a lack of standardization.
Conclusions:
- Commercial anti-rubella virus IgG assays exhibit poor standardization, with significant variability in quantitative results despite using the same international standard.
- The current level of standardization challenges the clinical relevance of quantifying anti-rubella virus IgG using existing commercial assays.
- Reevaluation of the necessity and methodology for quantifying anti-rubella virus IgG may be warranted for the scientific community.
Abstract:
Since the 1980s, commercial anti-rubella virus IgG assays have been calibrated against a WHO International Standard and results have been reported in international units per milliliter (IU/ml). Laboratories testing routine patients' samples collected 100 samples that gave anti-rubella virus IgG results of 40 IU/ml or less from each of five different commercial immunoassays (CIA). The total of 500 quantitative results obtained from 100 samples from each CIA were compared with results obtained from an in-house enzyme immunoassay (IH-EIA) calibrated using the WHO standard. All 500 samples were screened using a hemagglutination inhibition assay (HAI). Any sample having an HAI titer of 1:8 or less was assigned a negative anti-rubella virus antibody status. If the HAI titer was greater than 1:8, the sample was tested in an immunoblot (IB) assay. If the IB result was negative, the sample was assigned a negative anti-rubella virus IgG status; otherwise, the sample was assigned a positive status. Concordance between the CIA qualitative results and the assigned negative status ranged from 50.0 to 93.8% and 74.5 to 97.8% for the assigned positive status. Using a receiver operating characteristic analysis with the cutoff set at 10 IU/ml, the estimated sensitivity and specificity ranged from 70.2 to 91.2% and 65.9 to 100%, respectively. There was poor correlation between the quantitative CIA results and those obtained by the IH-EIA, with the coefficient of determination (R(2)) ranging from 0.002 to 0.413. Although CIAs have been calibrated with the same international standard for more than 2 decades, the level of standardization continues to be poor. It may be time for the scientific community to reevaluate the relevance of quantification of anti-rubella virus IgG.
