Making IGRA testing easier: First performance report of QIAreach QFT for tuberculosis infection diagnosis

Making IGRA testing easier: First performance report of QIAreach QFT for tuberculosis infection diagnosis Tuberculosis (TB), with around 1.4 million deaths, is one of the most important leading killer for infectious diseases in the world.Moreover, a quarter of the world population is estimated to live with TB infection (TBI).1,2 TBI is considered the reservoir of active TB, therefore, diagnosing and treating TBI is a crucial component of the End TB Strategy to achieve TB control.3 So far, the diagnosis of TBI is based on tuberculin skin test and on interferon (IFN)-g release assays (IGRAs) such as T-SPOT.TB and Quantiferon-TB Plus (QFT-Plus). 4 However, costs, complexity, and supply chain requirements hamper the implementation of current tests for TBI in decentralized settings.Therefore, there is an urgent need for accelerating the scale-up of such assays to inform test-and-treat algorithms for TBI. 5 The QIAreach QFT test is a novel and simplified version of QFT-Plus.Indeed, it uses a single tube corresponding to the TB2 tube of the QFT-Plus.However, unlike QFT-Plus, the test provides a qualitative result through a fluorescence lateral flow reader, which is transportable, easy to use and does not need highly trained personnel.6,7 The assay time to result (TTR) is around 20 minutes.Therefore, the QIAreach QFT test has the potentials to be a point-of-care test.The paper of Fukushima et al 7 aimed to evaluate the accuracy of the QIAreach QFT test for the detection of TBI compared to the commercial QFT-Plus test in both immunocompetent and immunocompromised individuals.The authors evaluate the tests' clinical performance in patients with active TB, used as a surrogate for TBI.Compared to QFT-Plus, which was used as reference standard, QIAreach QFT showed a 99% overall concordance and an optimal accuracy with 100% sensitivity and 98% specificity, similar to QFT-Plus 4. Interestingly, QIAreach QFT also scored positive in samples with IFN-g level falling in the so-called uncertainty zone of the QFT-Plus.8 IFN-g level inversely correlated with TTR, suggesting that the TTR may be used as a surrogate marker for the IFN-g concentrations.The QIAreach QFT test also scored positive in individuals with CD4 counts <200 cells/ml, thus showing potential for immunocompromised individuals.