Predictive value for progression to tuberculosis by IGRA and TST in immigrant contacts

Abstract

The authors determined the positive predictive value (PPV) for progression to tuberculosis (TB) of two interferon-c release assays (IGRAs), QuantiFERON-TB1 Gold In-tube (QFT-GIT) and T-SPOT.TB1, and the tuberculin skin test (TST) in immigrants contacts.Immigrant close contacts of sputum smear-positive TB patients were included when aged o16 yrs and their TST result was o5 mm 0 or 3 months after diagnosis of the index patient.Contacts were followed for the next 2 yrs for development of TB disease.Of 339 immigrant contacts with TST o5 mm, 324 and 299 had valid results of QFT-GIT and T-SPOT.TB1, respectively. Nine contacts developed active TB. One patient had not been tested with TST, while another patient had not been tested with QFT-GIT and T-SPOT.TB1. The PPV for progression to TB during this period was 9/28853.1% (95% CI 1.3-5.0%) for TST o10 mm, 7/ 18453.8% (95% CI 1.7-5.9%) for TST o15 mm, 5/17852.8% (95% CI 1.0-4.6%) for QFT-GIT and 6/ 18153.3% (95% CI 1.3-5.3%) for T-SPOT.TB1. Sensitivity was 100%, 88%, 63% and 75%, respectively.The predictive values of QFT-GIT, T-SPOT.TB1 and TST for progression to TB disease among immigrant close contacts were comparable.

Interferon- release assays for the diagnosis of latent Mycobacterium tuberculosis infection: a systematic review and meta-analysis

“…Furthermore, evidence on the actual predictive value of the IGRAs (i.e. the relationship between having a positive or negative IGRA result and developing or not developing tuberculosis) is emerging [19][20][21][22]. To further support public health programmes, a continuous assessment of the use of IGRA for the diagnosis of LTBI is, therefore, needed.…”

“…In the majority of the evaluated studies, it was not possible to compare the NPV estimates for IGRAs to that of the TST results [19,21,22,45,46]. In particular, in two studies performed on HIV-infected persons, TST-negative individuals were excluded from the follow-up [19,22].…”

“…In their study, KIK et al [21] included 433 close immigrant, adult contacts in the Netherlands, none of whom was immunosuppressed. QFT-G-IT or T-SPOT1.TB was performed only in TST-positive patients or in persons with a known prior TST result o10 mm (n517).…”

Latent tuberculous screening of recent migrants attending language classes: a cohort study and cost analysis

“…One paper 17 tested progression in patients who were TST+ before IGRA, giving a different prior probability in that cohort relative to other cohorts where this dual testing strategy was not done.…”

Spectrum of latent tuberculosis — existing tests cannot resolve the underlying phenotypes

“…Thus, none of the existing tests can accurately identify the subgroup that is at risk of progression to disease. This is borne out by the sobering fact that IGRAs have been shown to have only a modest predictive ability, and several studies show similar (and rather low) rates of progression among individuals with positive TST and IGRA results [2][3][4][5][6] . For example, the incidence rate of active disease in TB contacts with positive IGRA results was 9.2 per 1000 person-years (PY) in the Gambia 2 , 20.5 per 1000 PY in Turkey 4 and 7.7 per 1000 PY in Colombia 6 .…”