Performance Of The Quantiferon (R)-Tb Gold In-Tube Assay In Tuberculin Skin Test Converters: A Prospective Cohort Study

OBJECTIVE : To investigate diagnostic agreement of the QuantiFERON (R)-TB Gold In-Tube (QFT-GIT) test in adult tuberculin skin test (TST) converters in a high tuberculosis (TB) burden setting.SETTING AND DE SIGN: We performed a case-cohort study from 2014 to 2016 in Uganda among residents who were not infected with Mycobacterium tuberculosis. Participants were followed up for 1 year, when they were retested to determine TST conversion. All TST converters and a random sample of participants from baseline were offered QFT-GIT testing.RESULTS : Of 368 enrolled participants, 61 (17%) converted their TST by 1 year. Among 61 converters, 42 were tested using QFT-GIT, 64% of whom were QFT-GIT-positive. Of 307 participants with a persistent negative TST, 48 were tested using QFT-GIT, 83% of whom were QFT-negative. Overall concordance of TST and QFT-GIT was moderate (kappa = 0.48, 95% CI 0.30-0.66). Converters with a conversion of >= 15 mm had a higher proportion of concordant QFT-GIT results (79%) than converters with increments of 10-14.9 mm (52%).CONCLUSION: Concordance between TST and QFT-GIT was moderate among TST converters in this urban African population. These findings call for improved tests that more accurately measure conversion to tuberculous infection.