Elevated Rates of Indeterminate Results on QuantiFERON-TB Gold Plus in COVID-19 Patients

Interferon gamma release assays are used to screen various patient populations for latent tuberculosis infection. In this issue of the Journal of Clinical Microbiology, J. D. Ward, C. Cornaby, and J. L. Schmitz (J Clin Microbiol 59:e00811-21, 2021, https://doi.org/10.1128/JCM.00811-21) investigated an increased indeterminate rate in the QuantiFERON-TB Gold Plus assay among COVID-19 patients that was independent of immunosuppressive agents and lymphopenia. In their study, COVID-19 patients with indeterminate QuantiFERON-TB Gold Plus results trended toward decreased survival as well as increased serum interleukin-6 (IL-6) and IL-10 levels, although the differences were not statistically significant. They suggest that this pattern of cytokine expression supports an impairment of Th1, specifically interferon gamma production, in critically ill COVID-19 patients, as indicated by indeterminate QuantiFERON-TB Gold Plus results. Clinicians should be aware of the increased rate of indeterminate QuantiFERON-TB Gold Plus results in critically ill COVID-19 patients.