[Comparison of tests results between T-SPOT.TB and QuantiFERON-TB Gold In-Tube in a contact investigation]

We compared T-SPOT.TB (T-SPOT) and QuantiFERON-TB Gold In-Tube (QFT-GIT) test results in a contact investigation.

The index case was a male lecturer at a vocational school in Tokyo. Chest X-ray examinations and T-SPOT tests were performed on all 397 contacts, and QFT-GIT was performed on a subset of these contact subjects.

Chest X-ray examination showed no evidence of tuberculosis in any subjects. Among 389 contacts that underwent T-SPOT testing, 5 showed a positive reaction, 3 showed borderline reactions (1 positive borderline and 2 negative borderline), and 381 were negative. Among 56 contacts tested using both QFT-GIT and T-SPOT, 4 were positive, 1 was borderline, and 51 were negative by QFT-GIT. By T-SPOT, 2 contacts were positive, 1 was borderline positive, and 53 were negative. Preventive chemotherapy was indicated for the 5 positive and 1 borderline positive contacts identified by the T-SPOT test.

Chest X-ray examination and the T-SPOT test did not identify the TB outbreak.

The majority of contact subjects were negative by both tests, suggesting that both have a high specificity in contact investigations. However, the moderate concordance rate indicates that further testing is necessary to fully evaluate these tests.