TABLE 7.
COMPARISON OF THE QUANTITATIVE RESULTS OF DISCORDANT AND CONCORDANT SPECIMENS
| Quantitative TST Result |
Quantitative QFT-GIT Result |
Quantitative T-Spot Result |
|||||||||
| Test Results | N | 0–4 mm | 5–9 mm | 10–14 mm | ≥15 mm* | <0.35 | 0.35–0.99 | ≥1† | ≥ 4 Spots | 5–7 Spots‡ | ≥8 Spots§ |
| All tests negative | 1,713 | 1,676 (97.8%) | 30 (1.8%) | 7 (0.4%) | 0 | 1,713 (100%) | 0 | 0 | 1,693 (98.8%) | 20 (1.2%) | 0 |
| One test positive | 69 | 35 (50.7%) | 19 (27.5%) | 14 (20.3%) | 48 (69.6%) | 16 (23.2%) | 5 (7.3%) | 53 (76.8%) | 1 (1.5%) | 15 (21.7%) | |
| TST only | 33 | 0 | 18 (54.6%) | 14 (42.4%) | 33 (100%) | 0 | 0 | 32 (97%) | 1 (3%) | 0 | |
| QFT-GIT only | 21 | 21 (100%) | 0 | 0 | 0 | 16 (76.2%) | 5 (23.8%) | 21 (100%) | 0 | 0 | |
| T-Spot only | 15 | 14 (93.3%) | 1 (6.7%) | 0 | 15 (100%) | 0 | 0 | 0 | 0 | 15 (100%) | |
| Two tests positive | 11 | 1 (9.1%) | 1 (9.1%) | 4 (36.4%) | 5 (45.5%) | 5 (45.5%) | 3 (27.3%) | 3 (27.3%) | 1 (9.1%) | 1 (9.1%) | 9 (81.8%) |
| TST and QFT-GIT | 2 | 0 | 0 | 1 (50%) | 1 (50%) | 0 | 1 (50%) | 1 (50%) | 1 (50%) | 1 (50%) | 0 |
| TST and T-Spot | 5 | 0 | 0 | 1 (20%) | 4 (80%) | 5 (100%) | 0 | 0 | 0 | 0 | 5 (100%) |
| QFT-GIT and T-Spot | 4 | 1 (25%) | 1 (25%) | 2 (50%) | 0 | 0 | 2 (50%) | 2 (50%) | 0 | 0 | 4 (100%) |
| All three tests positive | 10 | 0 | 0 | 2 (20%) | 8 (80%) | 0 | 3 (30%) | 7 (70%) | 0 | 0 | 10 (100%) |
Definition of abbreviations: QFT-GIT = QuantiFERON-TB Gold In-Tube test; T-Spot = T-SPOT.TB test; TST = tuberculin skin test.
*
χ2 (trend) for 15 mm compared with the other groups = 725.7; P < 0.0001.
†
χ2 (trend) for 1 compared with the other groups = 578.0; P < 0.0001.
‡
The 22 borderline T-Spot results were added into this analysis to have results for the five to seven spots category. A borderline T-Spot test result was coded as negative for the purpose of this analysis.
§
χ2 (trend) for eight spots compared with the other groups = 1005.2; P < 0.0001.