Figure 1.
Study flow diagram of screening and testing for latent tuberculosis infection.
At recruitment demographic data, past medical history, previous TB disease, BCG vaccination status and recent TB exposure were all recorded. TST = tuberculin skin test; QFT-GIT = QuantiFERON Gold in-Tube.
Table 1.
Concordance between TST, T-SPOT.TB and QFT-GIT results stratified by study visit and BCG vaccination status.
Figure 2.
The relationship between IGRA response and TST induration.
The distribution of positive IGRAs (pre- and post-TST) by size of TST induration. TST = tuberculin skin test; QFT-GIT = QuantiFERON Gold in-Tube.
Figure 3.
The relationship between the magnitude of IFN-γ response among individuals positive by both IGRAs at baseline.
Solid line represents linear correlation. QFT-GIT = QuantiFERON Gold in-Tube; IFN-γ = interferon-gamma; ESAT-6 = early secretory antigenic target-6; CFP-10 = culture filtrate protein-10; IU = international units; SFC = spot forming cells.
Figure 4.
IGRA responses before and after TST administration.
(A) IFN-γ responses detected by QFT-GIT in individuals who became positive following TST; (B) SFC numbers in response to ESAT-6 and CFP-10 in individuals who became positive by T-SPOT.TB following TST; (C) SFC numbers in response to ESAT-6 and CFP-10 in individuals who became negative by T-SPOT.TB following TST. Uncertainty zone (grey shaded area); threshold for QFT-GIT positivity (dashed line); upper and lower thresholds for T-SPOT.TB conversion (solid lines). TST = tuberculin skin test; QFT-GIT = QuantiFERON Gold in-Tube; IFN-γ = interferon-gamma; ESAT-6 = early secretory antigenic target-6; CFP-10 = culture filtrate protein-10; IU = international units; SFC = spot forming cells.
Table 2.
Frequency of IGRA conversions and reversions following TST administration and stratified by baseline QFT-GIT and T-SPOT.TB responses.
Figure 5.
IGRA responses following LTBI treatment in individuals positive by IGRA at any stage of the study.
(A) SFC numbers detected to ESAT-6 by T-SPOT.TB; (B) SFC numbers detected to CFP-10 by T-SPOT.TB; bars = medians; (C) IFN-γ responses detected by QFT-GIT in individuals who were initially positive at day 0 compared to day 200 (left) and IFN-γ responses detected by QFT-GIT in individuals who were positive at day 7 compared to day 200. In each case samples from the same individual at these two times are linked by bars. QFT-GIT = QuantiFERON Gold in-Tube; IFN-γ = interferon-gamma; ESAT-6 = early secretory antigenic target-6; CFP-10 = culture filtrate protein-10; IU = international units; SFC = spot forming cells; Rx = treatment.
Table 3.
Proposed groups classified by IGRA response following TST administration, with suggested possible immune mechanisms.