Diagnostic value of T-SPOT.TB interferon-γ release assays for active tuberculosis
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- Published online on: April 30, 2015 https://doi.org/10.3892/etm.2015.2463
- Pages: 345-351
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Abstract
The aim of the present study was to evaluate the diagnostic value of interferon-γ release assays for the detection of active tuberculosis (ATB) in patients previously vaccinated with Bacillus Calmette‑Guérin (BCG). In total, 540 patients underwent the T‑SPOT.TB test, including 295 patients with active pulmonary TB (PTB), 52 patients with active extrapulmonary TB (EPTB), 11 individuals with inactive TB and 182 non‑TB cases. Simultaneously, 186 patients with ATB, including PTB and EPTB cases, and 125 non‑TB patients underwent tuberculin skin tests (TST). Associations between the sensitivity of the T‑SPOT.TB assays and lung lesion severity, positive smear grade, disease site and the duration of anti‑TB treatment were evaluated. The sensitivity and specificity values of the T‑SPOT.TB assay for diagnosing ATB were 76.66 and 76.37%, respectively, and the positive rate in the inactive TB test results was significantly lower (23.63%; P<0.001). The diagnostic sensitivity was higher in the PTB cases when compared with the EPTB cases (P=0.01). Furthermore, the diagnostic sensitivity of the ATB cases undergoing anti‑TB treatment was significantly lower when compared with the cases not undergoing treatment (P=0.002), and the sensitivity gradually decreased with the treatment duration (P=0.01). In addition, a statistically significant difference was identified in the specificity between the T‑SPOT.TB assay and the TST (76.37 vs. 51.15%; P<0.001), whereas the sensitivity values did not differ significantly (76.66 vs. 75.56%). Therefore, the results indicated that the T‑SPOT.TB assay is a promising diagnostic test for active PTB in a BCG‑vaccinated population, and should replace the TST. As the administration of anti‑TB treatment resulted in a lower sensitivity to the diagnostic test, the T‑SPOT.TB assay may also be suitable for the assessment of treatment outcomes.
