Table 4.
Performance of T-SPOT.TB in detecting pulmonary tuberculosis patients with different acid-fast bacilli smear and/or Xpert MTB/RIF status.
| AFB smear/Xpert status (N)* | T-SPOT status | Sensitivity % (95% CI) | Positive/total | Specificity% (95% CI) | Negative/total | PPV % (95% CI) | NPV % (95% CI) | Specificity in NTM cases %(n/N) |
|---|---|---|---|---|---|---|---|---|
|
AFB+
(56) |
T-SPOTMDC | 84.1 (73.3-94.9) | 37/44 | 25 (0.5-49.5) |
3/12 | 80.4 (69.0-91.9) |
30 (1.6-58.4) |
60.0 (3/5) |
| TBAg/PHA≥0.3 | 20.5 (8.5-32.4) | 9/44 | 83.3 (62.3-104.4) |
10/12 | 81.8 (59.0-104.6) |
22.2 (10.1-34.4) |
100 (5/5) |
|
|
AFB-
(1,959) |
T-SPOTMDC | 80.7 (74.9-86.5) | 142/176 | 69.4 (67.2-71.5) |
1,237/1,783 | 20.6 (17.6-23.7) |
97.3 (96.4-98.2) |
100 (15/15) |
| TBAg/PHA≥0.3 | 29.0 (22.3-35.7) | 51/176 | 94.8 (93.8-95.9) |
1,691/1,783 | 35.7 (27.8-43.5) |
93.1 (92.0-94.3) |
100 (15/15) |
|
|
Xpert+
(262) |
T-SPOTMDC | 83.1 (77.5-88.6) | 147/177 | 31.8 (21.9-41.7) |
27/85 | 71.7 (65.5-77.9) |
47.4 (34.4-60.3) |
No NTM |
| TBAg/PHA≥0.3 | 29.9 (23.2-36.7) | 53/177 | 76.5 (67.5-85.5) |
65/85 | 72.6 (62.4-82.8) |
34.4 (27.6-41.2) |
No NTM | |
|
Xpert-
(1,753) |
T-SPOTMDC | 74.4 (61.4-87.5) |
32/43 | 71.0 (68.8-73.1) |
1,213/1,710 | 6.1 (4.0-8.1) |
99.1 (98.6-99.6) |
90.0 (18/20) |
| TBAg/PHA≥0.3 | 16.3 (5.2-27.3) |
7/43 | 95.7 (94.7-96.6) |
1,636/1,710 | 8.6 (2.5-14.8) |
97.9 (97.2-98.5) |
100 (20/20) |
|
|
AFB-/Xpert-
(1,748) |
T-SPOTMDC | 74.4 (61.4-87.5) |
32/43 | 71.0 (68.8-73.1) |
1,210/1,705 | 6.1 (4.0-8.1) |
99.1 (98.6-99.6) |
100 (20/20) |
| TBAg/PHA≥0.3 | 16.3 (5.2-27.3) |
7/43 | 95.7 (94.7-96.6) |
1,631/1,705 | 8.6 (2.5-14.8) |
97.8 (97.1-98.5) |
100 (15/15) |
|
|
AFB+/Xpert+
(51) |
T-SPOTMDC | 84.1 (73.3-94.9) | 37/44 | 0.0 (0.0-0.0) |
0/7 | 84.1 (73.3-94.9) |
0.0 (0.0-.00) |
No NTM |
| TBAg/PHA≥0.3 | 20.5 (8.5-32.4) |
9/44 | 71.4 (38.0-104.9) |
5/7 | 81.8 (59.0-104.6) |
12.5 (2.3-22.8) |
No NTM | |
|
AFB+/Xpert-†
(5) |
T-SPOTMDC | N/A | . | 60 (17.1-102.9) |
3/5 | 0 (0-0) |
100 (100-100) |
60 (3/5) |
| TBAg/PHA≥0.3 | N/A | . | 100 (100-100) |
5/5 | N/A | 100 (100-100) |
100 (5/5) |
|
|
AFB-/Xpert+
(211) |
T-SPOTMDC | 82.7 (76.3-89.1) |
110/133 | 34.6 (24.1-45.2) |
27/78 | 68.3 (61.1-75.5) |
54 (40.2-67.8) |
No NTM |
| TBAg/PHA≥0.3 | 33.1 (25.1-41.1) |
44/133 | 59.1 (44.6-73.6) |
26/44 | 71.0 (59.7-82.3) |
22.6 (15.0-30.3) |
No NTM |
A total of 2,044 patients had BALF and/or sputum AFB smear, culture, and Xpert assays, as well as peripheral blood mononuclear cell T-SPOT performed concurrently. For strict comparison of the performance of T-SPOT in patients with different AFB smear and Xpert status, only the first AFB smear, Xpert, and T-SPOT results were used in the analysis. Twenty-nine patients with invalid T-SPOT results (PHA spot forming cells <20) were excluded from the analysis, including 7 culture-confirmed MTB cases (1 AFB+/Xpert-, 4 AFB-/Xpert+, and 2 AFB-/Xpert-), 1 NTM cases with AFB+/Xpert-, and 21 culture-negative cases (1 AFB-/Xpert+ and 20 AFB-/Xpert-). Pulmonary tuberculosis was defined as at least one of the BALF and/or sputum specimens having one positive culture result for M. tuberculosis. *Number of patients with different AFB smear and Xpert status. †No tuberculosis cases. AFB, acid-fast bacilli; AFB+, AFB smear positive; AFB–, AFB smear negative; Xpert, Xpert MTB/RIF; Xpert+, Xpert positive; Xpert–, Xpert negative; PPV, positive predictive value; NPV, negative predictive value; NTM, nontuberculous mycobacteria; CI, confidence interval; N/A, not applicable; T-SPOT, T-SPOT.TB; BALF, bronchoalveolar lavage fluid; MTB, M. tuberculosis.