Prevalence and Correlates of Latent Tuberculosis Infection Among Healthcare Workers at the University Hospital in Monterrey, Mexico

Abstract Background: Healthcare workers (HCWs) are at an increased risk of developing tuberculosis (TB) infection due to frequent exposure to patients infected with Mycobacterium tuberculosis (M.tb). Most HCWs who become infected develop latent tuberculosis infection (LTBI). Therefore, periodic screening for LTBI in this population is a crucial public health strategy and necessary for infection control in high TB burden countries. Objective: This study seeks to determine the prevalence and associated risk factors of LTBI among HCWs by using QuantiFERON-TB Gold Plus (QFT) and Tuberculin Skin Test (TST). Methods: A cross-sectional study of HCWs (n = 178) was conducted at the University Hospital of the Autonomous University of Nuevo León (UANL) in Monterrey, Mexico from 2017 to 2019. Medical students, resident physicians, social service interns, practicing nurses, nursing students, and administrative staff rotating or working in the emergency department or internal medicine ward were approached for recruitment. Participants who met the eligibility criteria were tested at baseline using both QFT and TST, and those who tested positive were considered to have LTBI. Negative tests were repeated at a follow-up encounter over the following 4 – 18 months. Demographic information was verbally collected. Logistic regression models were used to test for associations between independent variables and results of baseline and follow-up test results. Results: A total of 178 participants were included in this study. At baseline, the prevalence of LTBI was 59.6% (n = 106). Higher risk of LTBI at baseline was associated with males (OR: 2.0 [95% CI: 1.1 – 4.7]) and practicing nurses (OR: 2.9 [95% CI: 1.1 – 8.1]). Participants who had either a negative TST or QFT result at baseline (n = 91) followed up for a repeat test. Over the following 4 – 18 months, the cumulative incidence was 31.9% (n = 29). The agreement between the two tests was 0.42 using kappa coefficients, with greater likelihood for a QFT- TST+ result (OR: 2.2 [95% CI: 1.3 – 3.9]) via McNemar's test. Conclusion: This study showed that there was a high prevalence and incidence of LTBI among HCWs at the University Hospital at UANL in Monterrey, Mexico from 2017 to 2019. Our results suggest that higher LTBI prevalence may be associated with more frequent patient interactions. Active surveillance via periodic screening of TB infection in HCWs is essential to reduce future nosocomial TB incidences, especially in high TB burden countries.