Although the new interferon-gamma release assay QuantiFERON-TB Gold Plus® (QFT-Plus) had good sensitivity in children with pulmonary tuberculosis (TB) only, QFT-Plus had poor sensitivity in children with extra-pulmonary TB only, according to a study published in PLoS One. Further, findings indicated that positive QFT-Plus results may be associated with age, previous TB disease history, and TB-related chest radiography abnormalities.

QFT-Plus has shown reliable performance in adults, and the current study was designed to evaluate its performance in children. Data assessed were taken from patients suspected of having TB, who were aged between 2 months to 16.8 years, with QFT-Plus results and who had been admitted or screened at the National Lung Hospital in Ha Noi, Vietnam in 2017. Characteristics associated with positive QFT-Plus results were determined by performing multiple logistic regression modeling analyses. Researchers calculated overall sensitivity and sensitivity in pulmonary TB only, extra-pulmonary TB only, and both pulmonary TB and extra-pulmonary TB subgroups.

Of the 222 participants with available QFT-Plus results, 33 had confirmed cases of TB. Of these, 18 had QFT-Plus positive results and 15 had QFT-Plus negative results. Age, previous TB disease history, and confirmed TB were all significantly associated with positive QFT-Plus results with an area under the ROC curve of 0.77. Regardless of pulmonary TB or extra-pulmonary TB, the overall QFT-Plus sensitivity in children was 54.5%. QFT-Plus sensitivity in pulmonary TB only patients was 84.2% compared with 14.3% in extra-pulmonary TB only patients and 14.3% in both pulmonary tuberculosis and extra-pulmonary TB patients.

Limitations included a potential classification bias, a potential for findings to not be generalizable, and a potential for misdiagnosis.

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Study investigators concluded, “Although the QFT-Plus assay had rather good sensitivity in the subgroup of patients with exclusive [pulmonary tuberculosis], the assay had poor sensitivity in [extra-pulmonary tuberculosis] patients. Our findings also indicated that the patient’s age, history of previous [tuberculosis] disease, and [tuberculosis]-related abnormalities on chest radiography may be associated with a positive QFT-Plus result.”

Reference

Nguyen DT, Phan H, Trinh T, et al. Sensitivity and characteristics associated with positive QuantiFERON-TB Gold-Plus assay in children with confirmed tuberculosis [published online March 4, 2019]. PLoS One. doi: 10.1371/journal.pone.0213304