QuantiFERON-TB Gold Plus CLIA vs. T-SPOT.TB in patients with immunosuppressive conditions

<bold>Introduction:</bold> Guidelines recommend Interferon-gamma release assays (IGRAs) for diagnostic testing for latent tuberculosis infection (LTBI) in immunocompromised patients or those at increased risk of tuberculosis. We compared QuantiFERON-TB Gold Plus™ CLIA (QFT) and T-SPOT.TB™ (TSTB) in patients with immunosuppressive conditions. <bold>Methods:</bold> From September 2022 to December 2023 we included 3748 patients (1894 female [50.53%], 1854 male [49.46%]). QFT and TSTB were carried out according to the manufacturer’s instructions. Cohen’s Kappa (κ) was used to agreement assess. <bold>Results:</bold> <fig><object-id>erj;64/suppl_68/PA1478/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig> The percentage of patients with a positive-IGRA result was 13.39% (502/3748). Positive rates were 12.05% and 9.9% for QFT and TSTB, respectively. Figures for indeterminate results were 1.76% and 2.6% Overall agreement between QFT and TSTB was 93% (3486/3748), κ= 0.811 [95% CI 0.779-0.844]; whereas in IGRA-positive results was 63.4% (321/502, k=0.629 [95% CI 0.568–0.690]. With regard to QFT and TSTB discrepancies (262/3748[6.99%]), the percentage of results QFT-positive/TSTB-negative or indeterminate and TSTB-positive/QTF-negative or indeterminate were 26.09% and 9.9% <bold>Conclusions:</bold> In spite of substantial strength of agreement achieved, the amount of indeterminate and discordant results that could lead to misdiagnosis of LTBI evidence the benefit of implementing two IGRAs simultaneously to maximize sensitivity in patients at increased risk of tuberculosis.