Objectives: We compared the performance of a new interferon gamma release assay (IGRA) format assay, the ichroma™ COVID-19 IGRA (IGRA-SARS), with that of the widely used QuantiFERON SARS-CoV-2 ELISA kit (QFN-SARS) in vaccinated healthcare workers (HCWs). Additionally, we analyzed the long-term changes in IGRA results after the final vaccine dose. Methods: A total of 383 specimens from 281 HCWs were enrolled in this study, and the results of SARS-IGRA and QFN-SARS assays were compared. In addition, we performed the receive operator curve analysis to estimate the optimal cut-off value for IGRA-SARS. Results: For all specimens, IGRA-SARS and QFN-SARS showed 75.7% and 64.2% of the positive results, respectively. The absolute agreement between IGRA-SARS and QFN-SARS was 80.0%, and the Fleiss' κ value was 0.525, indicating moderate agreement. ROC curve analysis of the IGRA-SARS results showed a cut-off value of >0.254 IU/mL, which was consistent with the manufacturer's specifications. The positive rates of both IGRA assays decreased significantly after a postvaccination period of 6 months. Conclusions: IGRA-SARS showed acceptable performance in the detection of vaccine-induced immunity against COVID-19; however, harmonization of IGRA assays has not yet been achieved. Additionally, the significant decline of positive rates of IGRA after the last vaccination would support the necessity of booster vaccination after a postvaccination period of 6 months.
CITATION STYLE
Lim, Y. K., Kweon, O. J., Choi, Y., Kim, T. H., & Lee, M. K. (2023). Evaluation of ichromaTM COVID-19 interferon gamma release assay for detection of vaccine-induced immunity in healthcare workers. Clinical Chemistry and Laboratory Medicine, 61(3), 503–509. https://doi.org/10.1515/cclm-2022-0914
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