PT  - JOURNAL ARTICLE
AU  - D.I. Ling
AU  - M. Pai
AU  - V. Davids
AU  - L. Brunet
AU  - L. Lenders
AU  - R. Meldau
AU  - G. Calligaro
AU  - B. Allwood
AU  - R. van Zyl-Smit
AU  - J. Peter
AU  - E. Bateman
AU  - R. Dawson
AU  - K. Dheda
TI  - Are interferon-γ release assays useful for active tuberculosis in a high-burden setting?
AID  - 10.1183/09031936.00181610
DP  - 2011 Jan 01
TA  - European Respiratory Journal
PG  - erj01816-2010
4099  - http://erj.ersjournals.com/content/early/2011/02/24/09031936.00181610.short
4100  - http://erj.ersjournals.com/content/early/2011/02/24/09031936.00181610.full
AB  - Although intended for latent tuberculosis (TB), we hypothesized that in a high-burden setting: (i) the magnitude of response when using interferon-γ-release-assays (IGRAs) can distinguish active TB from other diagnoses, (ii) that IGRAs may aid in the diagnosis of smear-negative TB and (iii) that IGRAs could be useful as rule-out tests for active TB.We evaluated the accuracy of two IGRAs [QuantiFERON-TB Gold In-Tube (QFT-GIT) and TSPOT.TB] in 395 patients (27% HIV-infected) with suspected TB in Cape Town, South Africa.IGRA sensitivity and specificity (95% CI) were: QFT-GIT [76% (68,83) and 42% (36,49)] and TSPOT.TB [84% (77,90) and 47% (40,53)], respectively. Although IFN-γ responses were significantly higher in the TB versus non-TB groups (p<0.0001), varying the cutpoints did not improve discriminatory ability. In culture-negative patients, depending on whether those with clinically-diagnosed TB were included or excluded from the analysis, the NPV of QFT-GIT, TSPOT.TB and chest x-ray (CXR) in smear-negative patients varied between 85–89%, 87–92% and 98%, respectively. Overall accuracy was independent of HIV status and CD4 count.In a high-burden setting, IGRAs when used alone do not have value as rule-in or rule-out tests for active TB. In smear-negative patients, the CXR had better NPV even in HIV-infected patients.