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

, 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.