Interferon gamma release assay results and outcomes in COVID-19 patients

ABSTRACT

Introduction/Aim: The interferon gamma release assay (IGRA), used in diagnosing latent tuberculosis infections (LTBI), relies on the release of interferon gamma from T-cells exposed to M. tuberculosis specific peptides. An 'indeterminate' IGRA result is most commonly due an inadequate control (or 'mitogen') response, which may reflect underlying T-cell dysfunction, that is potentially associated with markers of severity in patients with COVID-19. The aim of this study was to determine associations and predictors of an indeterminate IGRA in hospitalised patients with COVID-19. Method(s) We performed a single centre, retrospective study on COVID-19 patients admitted to a tertiary referral hospital who had IGRA testing performed over a 5 months period. Demographics, markers of COVID-19 severity and other parameters were recorded, along with outcomes of COVID-19 infection. The primary outcomes included predictors of indeterminate IGRA results and associations with COVID-19 outcomes (severity, length of stay and mortality). Result(s) A total of 181 patients were included for analysis. Outcomes of IGRA testing included negative (n = 117) and indeterminate (n = 60) results. Patients with a positive IGRA (n = 4) were excluded from analysis. The odds of an indeterminate IGRA were increased with a higher severity grade of COVID-19 (OR 2.5;95% CI 1.3-4.9), immunosuppression at baseline (OR 2.3;95% CI 1.1-4.7) and when IGRA testing was done after immunosuppression for COVID-19 was commenced (OR 1.4;95% CI 1.1-1.8). A longer length of stay was more likely with an indeterminate IGRA compared to a negative result (OR 1.08;95% CI 1.03-1.14), No difference in mortality between the two IGRA subgroups was found. Conclusion(s) Our study demonstrates an indeterminate IGRA was associated with markers of disease severity and immunosuppression. In this cohort an indeterminate result was also associated with worse COVID-19 outcomes in hospitalised patients. This result could potentially be used as a prognostic marker for patients admitted with COVID-19.