QuantiFERON-TB Gold In-Tube test conversions and reversions among tuberculosis patients and their household contacts in Addis Ababa: a one year follow-up study

Mulugeta Belay, Mengistu Legesse, Daniel Dagne, Adane Mihret, Yonas Bekele, Girmay Medhin, Gunnar Bjune, Fekadu Abebe

BackgroundQuantiFERON-TB Gold In-Tube® (QFT) test is used for the diagnosis of latent tuberculosis (TB) infection. Besides, QFT test could allow tracking changes in immune response among TB patients and their contacts. In high TB burden settings, reports on QFT conversions and reversions among TB patients and their contacts are limited. As part of a major project to study immune responses to TB infection, we investigated QFT test conversions and reversions among smear positive pulmonary TB patients and their household contacts over 12 months.MethodsWe followed a total of 107 HIV negative participants (33 patients and 74 contacts) in Addis Ababa. We did QFT test at baseline and 12 months later according to the manufacturer¿s instructions.ResultsAt baseline, 25/33 (75.8%) of the patients and 50/74 (67.6%) of the contacts were QFT positive. At 12 months, 2 more patients (1 test negative and 1 indeterminate) became test positive. Besides, 11/24 (45.8%) test negative contacts became positive. Only one patient and one contact who were test positive at baseline became test negative 12 months later. At 12 months, the proportions of test positives for patients and contacts were, therefore, 78.8% and 81.1%, respectively. Among contacts, the proportion of test positives at 12 months was significantly higher compared to the proportion at baseline (McNemar, p¿=¿0.006); similarly, the median IFN-¿ response significantly increased at 12 months compared with the baseline level (Wilcoxon matched-pairs signed rank test, p¿=¿0.01). Patients, however, had comparable median IFN-¿ levels at baseline and 12 months later (p¿=¿0.56).ConclusionNearly half of QFT negative household contacts at baseline became positive at 12 months. This suggests that repeated screening of QFT negative contacts may be needed for epidemiological studies and interventions of latent TB in an endemic setting. A large longitudinal study may be needed to confirm our observations.