Table 2.

Consistency of IGRA during the 4-week study period stratified by baseline IGRA result

Baseline IGRA resultTotal no. of subjectsOverall trend
ConsistentInconsistent
n (%)n (%)
QFT (IU/ml)
    Total3525 (71.4)10 (28.6)
    <0.22118 (85.7)3a (14.3)
    0.2–<0.35b21 (50.0)1a (50.0)
    0.35–0.7b51 (20.0)4c (80.0)
    >0.7–<3.031 (33.3)2c (66.7)
    ≥3.044 (100)0
T-SPOT (SFC)d
    Total3532 (91.4)3 (8.6)
    0–32424 (100)0
    4–5b11 (100)0
    6–8b21 (50.0)1c (50.0)
    9–2921 (50.0)1c (50.0)
    ≥3065 (83.3)1c (16.7)
  • a All conversions were unstable (increase across the diagnostic threshold of 0.35 IU/ml from a baseline IFN-γ concentration of <0.35 IU/ml and subsequent permanent decrease to below 0.35 IU/ml for the QFT).

  • b The ranges from 0.2 to 0.7 IU/ml and 4 to 8 SFC represent proposed borderline zones for the interpretation of repeated QFT and T-SPOT results, respectively.

  • c All reversions were definite (permanent decrease below 0.35 IU/ml from a baseline IFN-γ concentration of ≥0.35 IU/ml for the QFT, and permanent decrease below 6 SFC from an SFC count of ≥6 SFC for the T-SPOT).

  • d Maximum spot count either from the ESAT-6 or the CFP-10 panel (minus the negative control spot count), whichever was higher.