Table 2.
Consistency of IGRA during the 4-week study period stratified by baseline IGRA result
| Baseline IGRA result | Total no. of subjects | Overall trend |
|
|---|---|---|---|
| Consistent |
Inconsistent |
||
| n (%) | n (%) | ||
| QFT (IU/ml) | |||
| Total | 35 | 25 (71.4) | 10 (28.6) |
| <0.2 | 21 | 18 (85.7) | 3a (14.3) |
| 0.2–<0.35b | 2 | 1 (50.0) | 1a (50.0) |
| 0.35–0.7b | 5 | 1 (20.0) | 4c (80.0) |
| >0.7–<3.0 | 3 | 1 (33.3) | 2c (66.7) |
| ≥3.0 | 4 | 4 (100) | 0 |
| T-SPOT (SFC)d | |||
| Total | 35 | 32 (91.4) | 3 (8.6) |
| 0–3 | 24 | 24 (100) | 0 |
| 4–5b | 1 | 1 (100) | 0 |
| 6–8b | 2 | 1 (50.0) | 1c (50.0) |
| 9–29 | 2 | 1 (50.0) | 1c (50.0) |
| ≥30 | 6 | 5 (83.3) | 1c (16.7) |
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).
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.
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).
Maximum spot count either from the ESAT-6 or the CFP-10 panel (minus the negative control spot count), whichever was higher.