Enhancing tuberculosis surveillance in quarry workers: identifying vulnerable subgroups

Abstract

Background: Stone quarry workers and others exposed to silica are especially vulnerable to tuberculosis (TB). Silicosis is a known risk factor for TB disease, but other common comorbidities and habits such as diabetes and alcohol and tobacco consumption may increase risk. We aimed to estimate the risk of TB infection among stone quarry workers and to identify associated factors. Methods: An annual TB infection screening strategy using interferon-gamma release assay (IGRA) was implemented in 2018 for quarry workers in two high-incidence municipalities in Portugal. Workers with a first negative IGRA test were followed up and stratified by age group, preconditions including silicosis, diabetes and hypertension, and alcohol and tobacco abuse. Incidence rates and adjusted risks for TB infection were quantified using Cox regression hazard rates. Result: From 2018 to 2022, 997 stone quarry workers were screened for TB. Of those, 347 were negative in their first and performed at least one additional IGRA test, being included in the analysis. The overall rate of infection was 3.2 per 100 person-year. Silicosis, diabetes, and age above 45 years were independent risk factors for TB infection [adjusted hazard ratio (aHR) 2.9 (95% CI: 1.4–5.9), 2.9 (1.1–7.7), and 2.73 (1.1–6.6) respectively]. Conclusions: Silicosis and diabetes seem to be independent risk factors for TB infection and should be targeted to reduce the burden of TB further. We suggest periodic screening of TB infection in people with silicosis, but more broadly in all those exposed to silica, especially if they also have other comorbidities such as diabetes.