Performance of an Interferon-γ Release Assay-Based Test for Cell-Mediated Immunity to SARS-CoV-2

The study assessed the performance of an interferon-γ release assay (IGRA) for detecting cell-mediated immunity (CMI) to SARS-CoV-2 in 522 individuals, including 378 convalescent patients and 144 healthy controls. The IGRA test demonstrated good diagnostic performance, with sensitivity and specificity of 89% and 69% for spike peptides, and 89% and 87% for nucleocapsid peptides, respectively. It was found that baseline IFN-γ concentration improved specificity, though high white blood cell counts could confound results. The study suggests CMI testing, particularly with nucleocapsid peptides, could be useful for assessing past SARS-CoV-2 exposure. It also noted that severe COVID-19 symptoms were associated with higher IFN-γ production, antibody titers, and an increased risk of hair loss, highlighting the potential link between severe symptoms and transient hair loss post-infection. The study emphasizes the need for further research on T cell responses and the impact of virus re-exposure and vaccination on CMI testing.