SETTING: A chest disease centre in Istanbul, Turkey. OBJECTIVE: The diagnostic accuracy of interferon-gamma-based assays for Mycobacterium tuberculosis infection may be improved by using lower cut-off values for the tuberculin skin testing (TST), QuantiFERON-TB Gold (QFT) and T-SPOT.TB (T-SPOT) assays. DESIGN: Three assays, TST, QFT and T-SPOT, were evaluated for their diagnostic performance with respect to different cut-off values. This evaluation was carried out in a comparative study involving 100 patients with untreated culture-confirmed cavitary pulmonary tuberculosis (TB) and 47 healthy subjects. RESULTS: The sensitivities of the assays were: TST 70%, QFT 78% and T-SPOT 83.5%, while their specificities were TST 35%, QFT 89.4% and T-SPOT 84.8%. Both QFT and T-SPOT were significantly more specific than TST (both P < 0.001), but were similiar to each other (P = 0.5). Receiver operating characteristic analysis revealed that a cut-off value of 0.818 IU/ml for QFT maximises specificity without significant loss of test sensitivity. Using lower cut-off values for T-SPOT and TST, however, also increased the sensitivity of the assay but resulted in a significant decrease in specificity. CONCLUSION: Lower cut-off values for TST, QFT and T-SPOT increased the sensitivity of each assay, but only with a lower cut-off value for QFT could specificity be maintained.
SETTING: A chest disease centre in Istanbul, Turkey. OBJECTIVE: The diagnostic accuracy of interferon-gamma-based assays for Mycobacterium tuberculosis infection may be improved by using lower cut-off values for the tuberculin skin testing (TST), QuantiFERON-TB Gold (QFT) and T-SPOT.TB (T-SPOT) assays. DESIGN: Three assays, TST, QFT and T-SPOT, were evaluated for their diagnostic performance with respect to different cut-off values. This evaluation was carried out in a comparative study involving 100 patients with untreated culture-confirmed cavitary pulmonary tuberculosis (TB) and 47 healthy subjects. RESULTS: The sensitivities of the assays were: TST 70%, QFT 78% and T-SPOT 83.5%, while their specificities were TST 35%, QFT 89.4% and T-SPOT 84.8%. Both QFT and T-SPOT were significantly more specific than TST (both P < 0.001), but were similiar to each other (P = 0.5). Receiver operating characteristic analysis revealed that a cut-off value of 0.818 IU/ml for QFT maximises specificity without significant loss of test sensitivity. Using lower cut-off values for T-SPOT and TST, however, also increased the sensitivity of the assay but resulted in a significant decrease in specificity. CONCLUSION: Lower cut-off values for TST, QFT and T-SPOT increased the sensitivity of each assay, but only with a lower cut-off value for QFT could specificity be maintained.
Authors: D I Ling; M Pai; V Davids; L Brunet; L Lenders; R Meldau; G Calligaro; B Allwood; R van Zyl-Smit; J Peter; E Bateman; R Dawson; K Dheda Journal: Eur Respir J Date: 2011-02-24 Impact factor: 16.671
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Authors: John Z Metcalfe; Adithya Cattamanchi; Eric Vittinghoff; Christine Ho; Jennifer Grinsdale; Philip C Hopewell; L Masae Kawamura; Payam Nahid Journal: Am J Respir Crit Care Med Date: 2009-10-01 Impact factor: 21.405
Authors: Lance Turtle; Tim Kemp; Geraint R Davies; S Bertie Squire; Nick J Beeching; Michael B J Beadsworth Journal: Eur J Intern Med Date: 2012-02-07 Impact factor: 4.487