Table 5. Performance of TST and IGRAs stratified by CD4 T-cell count in patients without active TB infection.
| Country (assay) | No. | CD4 (mean cells/mm3) | TST +/total tested (%) | TST not read (%) | ELISA based IGRA +/total tested (%) | Indeterminate ELISA IGRA (%) | TS.TB +/ total tested | Indeterminate TS.TB IGRA (%) |
|---|---|---|---|---|---|---|---|---|
| USA24 (QFTGT) | 294 | 364 | 19/205 (9) | 89 (30) | 25/294 (8) | 15 (5) | NA | - |
| <100 | 0/21 (0) | 0/31 (0) | 5 (16) | |||||
| 100–350 | 7/83 (8) | 6/111 (5) | 4 (4) | |||||
| >350 | 12/101 (12) | 19/152 (12) | 6 (4) | |||||
| Spain29 (QFTGT) | 75 | 461 | 9/75 (12) | 0 (0) | 5/75 (7) | 1/75 (1) | 7/75 (9) | 1/75 (1) |
| <200 | 0/20 (0) | 0/20 (0) | NS | 1/20 (5) | NS | |||
| >200 | 9/55 (16) | 5/55 (9) | NS | 6/55 (11) | NS | |||
| Spain30 (QFTGT) | 135 | 300 | 9/135 (7) | NA | 13/135 (10) | 2 (1) | ||
| <100 | 0/21 (0) | 0/21 (0) | 2/21 (10) | |||||
| 101–300 | 0/47 (0) | 3/47 (6) | ||||||
| 301–500 | 3/29 (10) | 4/29 (14) | ||||||
| >500 | 6/38 (16) | 6/38 (16) | ||||||
| South Africa39 (QFTG)* | 74 | 392 | 35/67 (52) | 7 (9) | 32/74 (43) | 5 (7) | 38/73 (52) | 1 (1) |
| <200 | NS | NS (26) | NS | 9 (44) | NS | |||
| <250 | NS | 12 (33) | NS | 13 (54) | NS | |||
| <350 | NS | 24 (33) | NS | 25 (48) | NS | |||
| >350 | NS | NS | NS | NS | NS | |||
| Uganda38 (QFTGT) | 109 | 283 | 42/89 (47) | 20 (18) | 74/109 (68) | 4 (4) | 59/109 (54) | 4 (4) |
| <100 | 1/8 (12) | 1/10 (10) | 1 (10) | 7/10 (70) | 0 (0) | |||
| 100–250 | 9/27 (33) | 22/33 (67) | 0 (0) | 19/33 (58) | 2 (6) | |||
| >250 | 32/54 (59) | 51/66 (77) | 3 (5) | 33/66 (50) | 2 (3) |
*Proportion (%) of positive IGRA individuals within CD4 count stratification, denominator not available.
TST: tuberculin skin test; IGRA: interferon-γ release assay; TB: tuberculosis; ELISA: enzyme linked immunosorbent assay; TS.TB: T-SPOT.TB; QFTGT: QuantiFERON Gold in Tube; NA: not available; NS: not stated in text; QFTG: QuantiFERON Gold.