IGRA as a predictive factor of silent pulmonary changes in individuals following exposure to tuberculosis

We conducted a study on usefulness of the tuberculin skin test (TST) and the Quantiferon-TB Gold IT (QFT) tests as predictors of radiological changes after contact with tuberculosis.

The study group consisted of TB-exposed HCWs working in the Military Institute of Medicine (Warsaw, Poland). The usefulness of TST, QFT, and a combination of both tests was assessed for prediction of silent radiological findings.

83 previously TB-exposed participants were recruited. None of the participants had a history of active tuberculosis. Positive TST results were reported in 72 (86.8 %) participants, and positive QFTs were observed in 27 (32.5 %) cases. Chest radiographs revealed 23 findings specific for non-active tuberculosis in 18 (21.7 %) participants. The results of the QFTs were associated with the highest negative predictive value, positive predictive value, and positive likelihood ratio of silent chest X-ray findings suggestive of latent tuberculosis infection. Positive QFT was the only statistically significant variable that increases the odds ratio (OR-8.3) of the presence of typical of tuberculosis radiological changes in the lung.

A positive QFT result in an individual with no TB history who was exposed to tuberculosis in the past is associated with a significantly higher risk of clinically silent parenchymal lesions in lungs suggestive of previous tuberculosis.