Table 2.
Summary of tests and definitions used by community-based studies.
| Community-based study | Study location | Risk score used | Tests used | Cut-offs | Resister’ definition | Other definitions | LTBI definition |
|---|---|---|---|---|---|---|---|
| Cobat et al. (27) | Cape Town, South Africa | None. Risk is inferred from community exposure in a high incidence environment. | TST (2 TU, PPD RT23, Statens Serum Institut, Denmark) | TST: 0mm | TST = 0mm at baseline only. | TST > 0mm at baseline only. | |
| Gallant et al. (28) | Cape Town, South Africa | None. Risk is inferred from community exposure in a high incidence environment. | TST (2 TU, PPD RT23, Statens Serum Institut, Denmark) In-house IGRA |
TST: 5mm In-house IGRA: 63 pg/mL |
Double negatives at a single time point. TST < 5mm and IFN-γ response to BCG or PPD or ESAT-6 < 63 pg/mL. | TST ≥ 5mm, IFN-γ response to BCG or PPD or ESAT-6 > 63 pg/mL. | |
| Kroon et al. (29) | Cape Town, South Africa | None. Risk is inferred from community exposure in a high incidence environment. | TST (2 TU, PPD RT23, Statens Serum Institut, Denmark; 5 TU, PPD-S2, Tubersol, Sanofi Pasteur Limited, USA) QFT Gold Plus (QFT-Plus) |
TST: 5mm QFT-Plus: Criteria for negative QFT-plus result: 1) Nil ≤ 8.0, and 2) TB1 minus Nil <0.35 or ≥0.35 and <25% of Nil value, and 3) TB2 minus Nil <0.35 or 0.35 and <25% of Nil value, and 4) Mitogen minus Nil ≥ 0.5. Criteria for positive QFT-plus result either: 1) Nil ≤ 8.0, and 2) TB1 minus Nil ≥0.35 and ≥25% of Nil value, and 3) Any TB2 minus Nil 4) Any Mitogen minus Nil Or 1) Nil ≤ 8.0, and 2) Any TB1 minus Nil 3) TB2 minus Nil ≥0.35 and ≥25% of Nil value, 4) Any Mitogen minus Nil. |
HIV-1-infected persistently TB, tuberculin and IGRA negative (HITTIN): HIV+ persons who had experienced a period of very low CD4 counts, who had no symptoms or history of previous TB, had three consecutive negative IGRA readings, and a TST = 0mm. | HIV-1-infected IGRA positive tuberculin positive (HIT): HIV+persons who had experienced a period of very low CD4 counts, who had no symptoms or history of previous TB with two consecutive positive IGRA results and a TST ≥ 5mm. | |
| Mahomed et al. (30) | Worcester, South Africa | Risk was inferred from community exposure in a high incidence environment. A subset of participants reported current or prior household contact, mostly within three years of enrollment. | TST (2 TU, PPD RT23, Statens Serum Institut, Denmark) QFT-GIT |
TST: 5mm QFT-GIT: IFN-γ (TB Ag – Nil) at 0.35 IU/ml |
Focus of the study was on converters/incident TB cases. No definition of resister/nonconverter given. | Converters: IFN-γ (TB Ag – Nil) > 0.35 IU/ml and TST ≥ 5mm at baseline measurement. 50% had active follow-up (every 3 months), and 50% had passive follow-up (at 2 year visit). | |
| Nemes et al. (31) | Worcester, South Africa | Risk was inferred from community exposure in a high incidence environment. A subset of participants reported current or prior household contact, mostly within three years of enrollment. | QFT-GIT | QFT-GIT: IFN-γ (TB Ag – Nil) at 0.2, 0.35 and 0.7 IU/ml | Stringent nonconverters: IFN-γ (TB Ag – Nil) < 0.2 IU/ml at baseline, day 360, and day 720. |
Stringent QFT persistent positives: IFN-γ (TB Ag – Nil) > 0.7 IU/ml at baseline, day 360, and day 720. “Uncertain” converters: IFN-γ (TB Ag – Nil) < 0.35 IU/ml at baseline, and IFN-γ > 0.35 IU/ml at day 360, with at least one result within the uncertainty zone of 0.2-0.7 IU/ml. |
Stringent converters: IFN-γ (TB Ag – Nil) < 0.2 at baseline and > 0.7 at day 360). |
| Andrews et al. (32) | Worcester, Ceres & Robertson, South Africa | None. Risk is inferred from community exposure in a high incidence environment. | QFT-GIT | QFT-GIT: IFN-γ (TB Ag – Nil) at 0.35 and 4.0 IU/ml | Nonconverters: IFN-γ (TB Ag – Nil) < 0.35 IU/ml at baseline, day 336 and end of study. | Converters: IFN-γ (TB Ag – Nil) >4.00 IU/ml at baseline, day 336 and end of study. | |
| Simmons et al. (33) | North West Province, South Africa | None. Risk is inferred from work exposure in gold mines, a high incidence environment. | TST (2 TU, PPD RT23, Statens Serum Institut, Denmark) QFT-Plus |
TST: 0mm and 5mm QFT-Plus: Both antigen tube readings of IFN-γ (TB Ag – Nil) at 0.35 IU/ml |
"Uninfected" : Miners who had a negative QFT-Plus up to one year after baseline. A stricter definition was also used as those with a negative QFT-Plus and TST = 0 mm after one year of follow-up. | "TB infected": Miners who had a positive QFT-Plus up to one year after baseline. A stricter definition was also used as those with a postive QFT-Plus and a TST > 5mm after one year of follow up. | |
| Li et al. (34) | Beijing, China | None. Risk inferred from working at Beijing Chest Hospital ≥3 years | ELISPOT (T.SPOTTB; Oxford Immunotec) |
ELISPOT ≥24 spots for ESAT-6, CFP-10, or both |
“Highly exposed but uninfected” (HEBUI):
Negative ELISPOT at baseline only |
"Latent": Positive ELISPOT at baseline only |