QuantiFERON-TB Gold Plus Conversion Among Healthcare Workers: A Retrospective Cohort Study on Occupational and Metabolic Factors

Background: Healthcare workers (HCWs) remain at risk of occupational exposure to Mycobacterium tuberculosis. Although workplace-related risk factors have been extensively investigated, the contribution of host metabolic factors to tuberculosis infection (TBI) susceptibility remains poorly understood. This study evaluated QuantiFERON-TB Gold Plus (QFT-Plus) conversion and its association with demographic, occupational, and metabolic risk factors. Methods: A retrospective cohort study was conducted among 3309 HCWs undergoing annual routine occupational health surveillance at Policlinico Tor Vergata in Rome (Italy) from 2017 to 2025. Data included age, sex, job category, night-shift work, departmental risk level, and biochemical parameters (lipid profile, blood glucose, and vitamin D levels). Associations with QFT-Plus conversion were assessed using univariate analyses, binary logistic regression, and multivariate Cox regression models. Results: During follow-up, 87 participants (2.6%) experienced QFT-Plus conversion. In univariate analysis, age ≥ 40 years (3.98% vs. 1.50%; p < 0.001) and hypercholesterolemia (3.8% vs. 2.1%; p = 0.004) were significantly associated with conversion. However, neither variable remained statistically significant in multivariate analyses (age: p = 0.734; hypercholesterolemia: p = 0.834). Occupational factors, including job category, night-shift work, and assignment to high-risk departments, were not significantly associated with QFT-Plus conversion. Likewise, hyperglycemia and vitamin D deficiency showed no significant associations. Conclusions: QFT-Plus conversion incidence was low, supporting the effectiveness of current hospital infection control measures in this low-incidence setting. No demographic, occupational, or metabolic factor emerged as an independent predictor of conversion. These findings should be interpreted considering the limited number of conversion events and the multifactorial nature of TBI susceptibility.