Using IFN-gamma release assay to confirm tuberculin skin test improves the screening of latent tuberculosis infection in Italian healthcare workers.
BACKGROUND
Healthcare workers (HCWs) represent a tuberculosis (TB) risk group for a wide range of tasks in healthcare, even in countries with low TB incidence, like Italy. Latent Tuberculosis Infection (LTBI) screening programs are an important tool for TB prevention in these setting.


METHODS
A retrospective study under a LTBI screening program among HCWs at the Siena University Hospital (Italy), was conducted between September 2011 and July 2015. Tuberculin Skin Test (TST) was used as a first level examination; all TST-positive cases were tested with QuantiFERON-TB Gold In-Tube (QFT-GIT) test, together with a group of TST-negative subjects.


RESULTS
Among the 2136 HCWs screened, 144 (6.7 %) were TST-positive and therefore tested with QFT-GIT, confirming a positive result in 36 cases (25 %). Agreement between two tests was poor (k = 0.092; 95 %, Confidence Interval [CI]- 0.048-0.136, p = 0.002). Among TST-positive cases, discordant results occurred more frequently in BCG vaccinated than unvaccinated HCWs (86.3 %, p < 0.001). The probability of a QFT-GIT-positive result increased according to the TST diameter (p = 0.001). No putative risk factor was associated with LTBI occurrence.


CONCLUSIONS
The use of QFT-GIT test as a second step in TST-positive cases offers an appropriate tool for LTBI detection, especially among BCG-vaccinated HCWs.
Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena, Siena, Italy.
Raffaela
R
Olivieri
Medicina Preventiva e Sorveglianza Sanitaria, Dipartimento di Biotecnologie Mediche, Universita' degli Studi di Siena, Siena, Italy.
Sara
S
Scarnera
Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena, Siena, Italy.
Annalisa
A
Ciabattini
Medicina Preventiva e Sorveglianza Sanitaria, Dipartimento di Biotecnologie Mediche, Universita' degli Studi di Siena, Siena, Italy.
Giulia
G
De Vuono
Direzione Medica di Presidio, Azienda Ospedaliera Universitaria Senese, Siena, Italy.
Pietro
P
Manzi
Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena, Siena, Italy.
Gianni
G
Pozzi
Medicina Preventiva e Sorveglianza Sanitaria, Dipartimento di Biotecnologie Mediche, Universita' degli Studi di Siena, Siena, Italy.
Giuseppe
G
Battista
Laboratorio di Microbiologia Molecolare e Biotecnologia, Dipartimento di Biotecnologie Mediche, Università degli Studi di Siena, Siena, Italy.
Donata
D
Medaglini
Healthcare workers; Interferon-gamma release assays; LTBI; Tuberculosis