TABLE 1.
COMPARISON OF TESTS FOR LATENT TUBERCULOSIS INFECTION
| TST | QFT | T-SPOT.TB | |
|---|---|---|---|
| Relative sensitivity (drops with decreasing CD4+ T-cell count) | ++ | ++* | +++* |
| Specificity | + (for BCG vaccinated); +++ (for non-BCG) | +++ | +++ |
| Benefit of treating positives by IPT | Yes† | Unclear† | Unclear† |
| Reproducibility | + | +++ | +++ |
| Costs | + | +++ | +++ |
| Laboratory infrastructure required | No | Yes | Yes |
| Need for repeat visit | Yes | No | No |
| Trained personnel required | + | ++ | +++ |
Definition of abbreviations: IGRA = IFN-γ release assay; IPT = isoniazid preventive therapy; LTBI = latent tuberculosis infection; QFT = QuantiFERON-TB Gold In-Tube test; TST = tuberculin skin test.
Adapted from Reference 61.
+, indicates a comparison with other tests in Table 1.
Data are based on studies of persons with active TB disease, which may or may not correlate with persons having LTBI. Data are suggestive that QFT has a sensitivity similar to TST, while T-SPOT.TB may have increased sensitivity compared to TST, and the sensitivity of all three tests decreases with decreasing CD4+ T-cell count. However, prospective studies are needed in subjects with HIV to confirm that these findings can be applied to evaluating risk and initiating IPT.
There are no prospective trials of IGRAs evaluating the benefit of IPT.