IDSA Guidelines on Interferon-Gamma Release Assays for Latent Tuberculosis Infection

Key Guideline Recommendations

The IDSA/ATS/CDC guidelines consider QuantiFERON-TB Gold In-Tube and T-SPOT.TB to be equivalent interferon-gamma release assays (IGRAs) that can be used interchangeably for diagnosing latent tuberculosis infection, with no preference given to one IGRA over the other in official guidelines 1
The CDC states that both QuantiFERON-TB Gold In-Tube and T-SPOT.TB are FDA-approved IGRAs that may be used as aids in diagnosing M. tuberculosis infection, including both latent infection and active tuberculosis disease 2, 3

QuantiFERON-TB Gold In-Tube uses enzyme-linked immunosorbent assay (ELISA) methodology and measures the amount of interferon-γ in supernatant of whole blood cell suspension, with results available within 8-30 hours and requiring blood processing within 12 hours of collection 2, 5, 6
T-SPOT.TB uses enzyme-linked immunospot (ELISpot) methodology and counts the number of individual cells producing interferon-γ 2, 5

Both tests share key advantages over TST, including not being affected by prior BCG vaccination, requiring only one patient visit, and having no reader bias or placement errors 6, 7
The IDSA/ATS/CDC guidelines recommend performing an IGRA rather than tuberculin skin test (TST) in specific populations, including those likely to be infected with M. tuberculosis and having low or intermediate risk of disease progression, with a strong recommendation for individuals ≥5 years old 1, 4

Guidelines suggest considering dual testing with both IGRA and TST for patients at highest risk of progression to active TB, with a positive result from either test considered positive, increasing sensitivity at the cost of reduced specificity 1, 2, 8
Dual testing may also be considered for severely immunocompromised patients, with the goal of increasing sensitivity 1, 5, 7

The IDSA/ATS/CDC guidelines recommend selecting an IGRA based on local availability and laboratory capabilities, with both tests considered equivalent 1, 2
Consideration of T-SPOT.TB or QFT-GIT may be based on specific patient factors, such as severe immunocompromisation or high-dose corticosteroid use, although the guidelines do not provide a clear preference 1, 2, 4, 5