Prevalence of tuberculosis skin test positivity among healthcare workers: results of an observational study

Background. Tuberculosis is an infectious disease caused by the bacillus Mycobacterium tuberculosis. Healthcare workers (HCWs) are at risk of becoming infected and, in turn, becoming contagious. The aim of our study was to assess the prevalence of latent tuberculosis infection (LTBI) among HCWs and to identify associated factors, with the goal of defining the specific residual risk within work environments. Methods. The data from the health surveillance of HCWs between January 2017 and January 2020 were collected at the Policlinico Umberto I Hospital in Rome and used to assess the prevalence of LTBI through purified protein derivative (PPD) and interferon-gamma release assay (IGRA) tests (QuantiFERON®-TB Gold). Results. Out of 3,102 HCWs, the PPD was positive in 431 subjects (13.9%); however, out of 479 operators undergoing TB Gold, 42.8% were positive. The risk of testing positive for LTBI increased with age, particularly in the nursing profession and, in subjects over 50, among technicians. Conclusions. Our study identified a relatively high prevalence of LTBI, confirming that the risk among HCWs is higher than in the general population. Furthermore, the PPD test, despite having low specificity, can be considered a first-level screening tool in Italian hospitals, with positive results requiring confirmation by IGRA tests.