Diagnostic results and strategy for detecting active TB in the validation group.

<p>TB suspects were first tested with T-SPOT in step 1, then T-SPOT positive subjects were tested with long-term (72h) PPD-stimulated IFN-γ/IL-2 assays as step 2. The positive results of the two-step assay were defined when both test was positive and a negative result when either negative. The gold standard for ATB was based on positive <i>M</i>.<i>tuberculosis</i> culture or/and positive acid-fast bacillus smear (ATB group).The subjects without active TB were defined as NTB group.