VIDAS® TB-IGRA assay for diagnosing tuberculosis infection in people living with HIV: A preliminary study

Abstract

Background: The diagnosis of presumed latent tuberculosis (TB) infection (LTBI) is problematic in people living with HIV (PLWH) because of sub-optimal sensitivity and high indeterminate rates, especially in those with advanced immunosuppression. Better diagnostic tools for LTBI are needed in this sub-population.

Methods: We compared the sensitivity of VIDAS TB-IGRA, a fully automated RD1-specific new interferon-ϒ-release assay (IGRA), to QFT-Plus in 77 PLWH with active pulmonary TB who had varying CD4 counts. Sputum culture positivity served as the reference standard for active TB.

Results: The sensitivity of VIDAS TB-IGRA was similar to QFT-Plus overall [90.9% (70/77) vs 92.0% (69/75)], in those with CD4 <200 cells/mm³, [88.9% (40/45) vs 88.6% (39/44)], and in those with CD4 <100 [85.7% (18/21) vs 80.0% (16/20)]. However, VIDAS TB-IGRA had a higher sensitivity in those with CD4 <50 [92.3% (12/13) vs 75% (9/12)] and fewer indeterminate results overall [0 vs 2]. When the indeterminate results in this subgroup were regarded as negative, the comparative sensitivity was [92.3% (12/13) vs 69.2% (9/13)].

Conclusion: VIDAS TB-IGRA had a similar sensitivity to QFT-Plus in PLWH. Whether VIDAS TB-IGRA sensitivity is significantly better at lower CD4 counts remains to be confirmed in a larger study. These data have implications for the diagnosis of LTBI in those with advanced immunosuppression.

Keywords: Active TB; Diagnosis; Interferon-gamma release assay (IGRA); Latent TB infection; Tuberculosis.