Accuracy of QuantiFERON-TB Gold-PLUS Test for the Diagnosis of Mycobacterium tuberculosis infection in Children

Background. Compared to its predecessor QuantiFERON-TB Gold in Tube (QFT-IT), QuantiFERON-TB Gold Plus (QFT-Plus) contains an additional antigen tube (TB2), stimulating both CD4+ and CD8+ T-cells. The ability to discriminate CD4+ and CD8+ responses is suggested to be useful in differentiating stages of M. tuberculosis infection. While QFT-Plus has already been evaluated in adults, there are not enough data in children evaluated for suspected active tuberculosis (TB) or latent TB infection (LTBI).Methods. A prospective cross-sectional study was conducted among children aged 0 to 17 years who were evaluated for suspected active TB or screened for LTBI. All children underwent QFT-Plus and further clinical, radiological, microbiological analyses according to clinical scenario.Results. Of the 198 children enrolled, 43 (21.7 %) were tested because of suspicion of active TB: 12/43 (27.9%) were diagnosed with active TB, and among these 10/12 (83.3%) had a positive QFT-Plus assay. Of the 155 children screened for LTBI 18 (11.6%) had a positive QFT-Plus and 5 (2.5%) had an indeterminate result. TB1 and TB2 quantitative responses were not able to discriminate active disease from latent infection. The percent agreement between TB1 and TB2 was 100%.Conclusions. QFT-Plus assay showed good sensitivity for active TB and was particularly useful for the evaluation of children with suspected LTBI, giving a low rate of indeterminate results in this group. More studies are needed to properly evaluate QFT-Plus ability in discriminating active disease from latent infection.