Silicotuberculosis among Miners: A Scoping Review

Abstract

Background: Silicotuberculosis is both a Public Health and Occupational Health problem within the twenty-first century. Although diagnostic procedures used to screen for tuberculosis have evolved over the years, the Sputum Test remains the GOLD Standard, particularly in resource-limited settings. Studies have identified several risk factors associated with silicotuberculosis outcomes. However, the associated risk factors, mechanism of action related to silica dust exposure, and infection or activation of tuberculosis with host iron status remain unanswered, especially in the mine settings.

Objectives: This scoping review aims to map out the risk factors associated with silicotuberculosis and identify diagnostic techniques used in the screening of silicotuberculosis.

Methods: A systematic search to identify the available international evidence was conducted in the following databases: Medline, Cochrane Library, Embase, Cinahl, Georef, and grey literature sources. The search was limited to articles published in the English language and between 2000 to 2020. The reference lists of included articles were also searched for relevant articles. We included all primary studies conducted on miners exposed to silica dust. Diagnostic techniques to screen silicosis and tuberculosis were included with silicotuberculosis as the outcome. The abstracts and full articles were screened independently and in duplicates by two reviewers. One reviewer conducted the data entry. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses: Extension for Scoping Reviews (PRISMA-ScR) was adopted as a guide to present the study results.

Results: Twenty-eight articles met our inclusion criteria. Seventeen studies were from Southern Africa, and four studies from China. The study population consisted mainly of miners. Risk factors associated with tuberculosis outcomes reported by the reviewed studies included demographic factors (> 50 years of age, migrants from neighboring/foreign country, and race), lifestyle behavior (smoking, daily alcohol intake, and opium addiction), clinical factors (history of tuberculosis (TB) in the last five years, previous TB retreatment, site of diagnosed TB, positive QFT, silicosis characteristics, HIV CD4 counts, and respiratory symptoms) and occupational health and safety factors (cumulative respirable quartz, continuity of silica dust exposure, and exposure duration). A few studies used occupational history and differential diagnostics to diagnose silicotuberculosis. A few studies reported on NIOSH B readers in their methods of assessment. Several studies assessed silicotuberculosis outcome by the grading of silicotic nodules and a positive smear/culture result. A few studies highlighted latent tuberculosis, lung function loss, and the presence of mycobacterium tuberculosis-resistant strains among miners.

Conclusion: This scoping review highlights substantial gaps in the reviewed literature. It outlines a series of recommendations urgently needed to inform research and practice. Capacity building in developing countries is needed to prioritize training to certify physicians and invest in diagnostic tools that screen for latent tuberculosis. The findings highlight an urgent need for legal frameworks in low- and middle-income countries to establish adequate workers’ protection measures in small-scale mines. This scoping review identified a dearth of literature to explore risk factors that aggravate the consequences of silica dust exposure. Given the substantial deficit in studies assessing sex/gender differences within mine settings, there is an urgent research imperative for future studies to incorporate sex/gender analysis in investigating silico-tuberculosis among miners.