Table 2. Test characteristics.
| Type of IGRA (in-house or commercial); M tuberculosis antigens or peptides* |
IGRA cutoff † | TST cutoff(s) | Blinding to IGRA results |
|
|---|---|---|---|---|
| Doherty et al (2002)30 | WBA, ELISA (in house); PPD, ESAT 6 | 100 pg/mL | · · | Yes |
| Hill et al (2008)32 | ELISPOT (in house); ESAT6, CFP-10 | ~32 SFC | ≥10 mm | ‡NS |
| Bakir et al (2008)27 | ELISPOT (in house); ESAT6, CFP-10 | ~20 SFC | ≥5 mm | Yes |
| Aichelburg et al (2009)26 | WBA, ELISA (QFT-Gold in tube); ESAT6; CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL | · · | No |
| Kik et al (2009)35 | ELISPOT (T-SPOT.TB); ESAT6, CFP-10 | ≥8 SFU after negative well subtraction (~20 SFC) |
(inclusion criterion) | NS |
| Kik et al (2009)35 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/ml (~14 pg/mL) | ||
| Del Corral et al (2009)28 | WBA, ELISA (in house); CFP-10, CFP, Ag85A, Rv2031c | 22 pg/mL | ≥10 mm and ≥5 mm |
‡NS |
| Lienhardt et al (2010)37 | ELISPOT (in house); ESAT6, CFP-10 | ≥20 SFC after negative well subtraction and ≥32 SFC |
≥10 mm | Yes |
| Yoshiyama et al (2010)39 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL (~14 pg/mL) | · · | No |
| Leung et al (2010)36 | ELISPOT (T SPOT-TB); ESAT6, CFP-10 | ≥6 SFU (~20 SFC) | ≥5 mm, ≥10 mm, and ≥15 mm |
Yes |
| Harstad et al (2010)31 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL ( ~14 pg/mL) | (inclusion criterion) | No |
| Diel et al (2010)29 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL ( ~14 pg/mL) | ≥5 mm, ≥10 mm | No |
| Jonnalagadda et al (2010)33 | ELISPOT (T.SPOT.TB); ESAT6, CFP-10 | ≥6 SFU (~20 SFC) | · · | Yes |
| Joshi et al (2011)34 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL (~14 pg/mL) | ≥10 mm | §Yes |
| Mahomed et al (2011)38 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL (~14 pg/mL) | ≥10 mm | No |
| Costa et al (2011)40 | WBA, ELISA (QFT-Gold in tube); ESAT6, CFP-10, Rv2654c (p38–55) | ≥0·35 IU/mL (~14 pg/mL) | ≥0 mm | ¶No |
CFP=culture filtrate protein. ESAT=early secreted antigenic target. HIC=high-income country. LIC=low-income country, MIC=middle-income country, NS=not stated. TST=tuberculin skin test. PPD=purified protein derivative. WBA=whole-blood assay.
All measured interferon-gamma. Studies done in Turkey,27 Colombia,28 and South Africa38 described serial testing: interferon-γ release assay (IGRA) repeated at 6 months of follow-up, at 2 months of follow-up, and repeated for individuals with suspected tuberculosis, respectively.
Unit conversions given are equivalent to cutoffs defined in original papers: Hill et al32 (positive well with eight spot-forming units [SFU]> negative well; one pool of overlapping peptides must be positive); Bakir et al27 (≥5 mean spot-forming cells [SFC] in duplicate wells than negative wells and if number of SFCs was twice the mean of negative control wells). Incubation time was more than 24 h in the studies done in Ethiopia (120 h) and Colombia (168 h).
Although not reported, study investigators confirmed that clinicians were blinded to IGRA results.
Cases were not diagnosed by researchers, but health-care workers were aware of IGRA results.
Clinicians were not blinded to IGRA-positive results.