Low agreement between SARS-CoV-2 T-cell assays in immunocompromised individuals
T-cell responses are an important component of immunity against SARS-CoV-2, especially in people with compromised immune systems where antibody responses may be suboptimal. Commercial interferon-γ release assays (IGRAs) have become available to measure SARS-CoV-2–specific T-cell responses, but their reliability in such populations remains uncertain.
Audigé and colleagues assessed the agreement between two commercial T-cell assays—Euroimmun SARS-CoV-2 IGRA and Roche Elecsys IGRA SARS-CoV-2—in 81 participants from the Swiss HIV Cohort Study and the Swiss Transplant Cohort Study (62 samples from people with HIV [PWH] and 111 from solid organ transplant [SOT] recipients).
Across 173 blood samples, the two assays showed low overall agreement (Cohen’s κ = 0.20; overall percent agreement = 66%). Invalid results were frequent, particularly with the Euroimmun test (22% of samples) compared with Roche (8%). When excluding invalid results, agreement improved modestly (κ = 0.43; agreement = 90%). Invalid results were most common in recently transplanted SOT recipients, often due to failed positive controls, suggesting an influence of immunosuppression on assay performance.
In summary, this study found low concordance and frequent invalid results between two widely used SARS-CoV-2 T-cell assays in immunocompromised individuals. These findings highlight the need for optimization and validation of T-cell tests in vulnerable populations, where accurate assessment of cellular immunity is particularly important.