Characteristics of immune diagnostic tests for tuberculosis.
| Test Characteristics | TST | QFT-GIT | T-SPOT TB |
|---|---|---|---|
| Internal control | No | Yes | Yes |
| Mtb-specific antigen | No | Yes | Yes |
| Test substrate | skin | Whole blood | PBMC |
| Time required for results, h | 72 | 16–20 | 16–20 |
| Cells involved | Neutrophils, CD4, CD8 that transmigrate out of capillaries into the skin. Role of Treg [CD4+CD25highFoxP3+] (10–12) | CD4 T cells in vitro with effector memory and central memory phenotype | CD4 T cells in vitro with effector memory and central memory phenotype |
| Cytokines involved | IFN-γ, TNF-α, TNF-β (10, 11) | IFN-γ | IFN-γ |
| Overall sensitivity for TB infection | |||
| HIV-uninfected | 77% (32) | 70–80% (32) | 80–91% (32) |
| Overall specificity for TB infection | 59%/97% (32, 33) | 96% (32) | 93% (32) |
| Overall specificity for active TB | — | 79% (33) | 59% (33) |
| Criteria for conversion established by evidence | Yes | No | No |
| Cutoff established depending on age, immune suppression, BCG vaccination status | Yes | No | No |
| Ability to detect those at high risk of developing active TB | Weak (32, 37) | Weak (32, 37, 38) | Weak (32, 37, 38) |
Values in parentheses are reference numbers. TB: tuberculosis; BCG: bacillus Calmette Guerin; IFN: interferon; TNF: tumor necrosis factor; TST: tuberculin skin test; QFT-GIT: QuantiFERON TB Gold in tube; PBMC: peripheral blood mononuclear cells; HIV: human immunodeficiency virus.