Value of adding an IGRA to the TST to screen for latent tuberculous infection in Greek health care workers
OBJECTIVE: To evaluate the value of adding an interferon-gamma release assay (IGRA) to the tuberculin skin test (TST) for detecting latent tuberculous infection (LTBI) in a Greek university hospital among health care workers (HCWs) predominantly vaccinated with bacille Calmette-Guérin (BCG).
DESIGN: Of 788 HCWs enrolled, 68.1% were BCG-vaccinated. A TST 10 mm was considered positive and was followed by the QuantiFERON-TB® Gold In-Tube assay (QFT-GIT) in a two-step strategy.
RESULTS: Of the enrolled HCWs, 36.4% were TST-positive, of whom only 14.4% were IGRA-positive. Agreement between the tests was poor (κ = 0.019; 95%CI −0.014–0.05, P = 0.355). Both TST and IGRA positivity increased with TST diameter, from 5.7% in TST 10–14 mm to 48.8% in TST 20 mm. TST-positive, IGRA-negative results were most likely in younger, recently BCG-vaccinated HCWs (84.6% in those aged 20–29 years) and less likely in older HCWs (45% in those aged 50–59 years). The two-step strategy would have been more cost saving compared to the TST-only approach if adherence to LTBI treatment in our cohort had been 24%.
CONCLUSIONS: Poor overall agreement between TST and QFT-GIT was found. Use of IGRA as a second step in TST-positive cases offers an appropriate tool for LTBI detection among BCG-vaccinated HCWs in low-TB-incidence settings.
Document Type: Research Article
Affiliations: 1: Departments of Pulmonary Medicine 2: Family Medicine 3: Microbiology, University Hospital of Ioannina, Ioannina, Greece
Publication date: September 1, 2014
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