Table 2– Positive predictive value (PPV) of commercial interferon-γ release assays (IGRAs) for progression in those with latent Mycobacterium tuberculosis infection
First author [ref.]Study designParticipantsCountry (burden)IGRA(s) usedAge mean±sd# yrsPerformance of IGRA and TST testingFollow-up period monthsLater TB cases among untreated IGRA/TST positives n/N (PPV % (95% CI))Later TB cases among IGRA/TST-positives with confirmed relationship to index cases by RFLP n/N (%)
Clark 22Case–control201 immune-deficient HIV-1-positive adultsUK (low)T-SPOT®.TBMedian 40 (range 33–46)NA24T-SPOT®.TB: 2/20 (10 (0.012–0.32)); TST: NANA
Diel 20Cohort601 close contacts of AFB-positive TB cases (66 (10.9%) children <16 yrs)Germany (low)QFT-G-IT27.7±12.0 (range 1–56)Simultaneously with TST24 (mean)QFT-G-IT: 6/41 (14.6 (0.06–0.29)); 5/219 TST-positives >5 mm: (2.3 (0.007–0.052))QFT-G-IT: 2/6 (33.3); TST: 1/5 (20)
Aichelburg 19Cohort830 HIV-1-positive adultsAustria (low)QFT-G-IT39 (interquartile range 32–47)IGRA first, TST only if QFT-G-IT positive19 (mean)QFT-G-IT: 3/36+ (8.3 (0.018–0.22)); TST: NANA
Kik 21Cohort433 adult close immigrant contacts and BCG-vacc. Dutch-born contactsThe Netherlands (low)QFT-G-IT, T-SPOT®.TBNATST first, IGRA only if TST positive (at a cut-off ≥5 mm)§22ƒ (median)QFT-G-IT: 5/178 (2.8 (0.009–0.064)); T-SPOT®.TB: 6/181 (3.3 (0.012–0.07)); TST ≥10 mm: 9/288 (3.1 (0.014–0.058))##IGRAs: 3/3 (100)¶¶; TST: 6/6 (100)
  • TST: tuberculin skin test; TB: tuberculosis; RFLP: restriction fragment length polymorphism; NA: not assessed; AFB: acid-fast bacilli; QFT-G-IT: QuantiFERON®-TB Gold In-Tube assay; BCG: bacille Calmette–Guérin; vacc.: vaccinated. #: unless otherwise stated; : after subtraction of invalid results/indeterminates; +: among 44 QFT-G-IT-positive patients, seven were diagnosed with active TB during the first investigation and one was lost within the first 3 weeks of follow-up; §: conventional waiting period of 8 weeks was not respected for IGRAs or the TST; TST was repeated 8–12 weeks later if negative initially, but not the IGRA if the IGRA result was initially negative; ƒ: only 95 (53.4%) out of 178 of the QFT-G-IT-positive contacts and only 101 (55.8%) out of 181 of the T-SPOT®.TB-positive contacts were followed for 21 months; ##: as calculated by the authors of that study, although a TST was considered positive if induration diameter was ≥5 mm; ¶¶: six out of nine patients developing tuberculosis were culture-confirmed; two of them were negative by both IGRAs and, in one tuberculosis patient, culture-confirmed IGRA testing was not performed.