8288651 Exploration of the use of lymph node silicosis for the diagnosis of pulmonary silicosis

<h3>Objective</h3> Lymph node silicosis may be diagnosed incidentally during investigations of lung and mediastinal diseases. This study explored the diagnostic accuracy of lymph node silicosis for pulmonary silicosis in deceased South African gold miners. <h3>Methods</h3> Pathologist-diagnosed lymph node and pulmonary silicosis, and occupational histories of miners with exclusive gold mining service and who had an autopsy examination for compensation from 1975 to 2018 were selected from the Pathology Automation (PATHAUT) database. We calculated sensitivity, specificity, positive and negative predictive values (PPV and NPV) and summary diagnostic accuracy measures for lymph node silicosis overall and by employment duration, a surrogate for respirable crystalline silica (RCS) exposure. Pulmonary silicosis was the reference standard. <h3>Results</h3> Of the 69 802 miners selected, 39.2% (n = 27373) had lymph node silicosis and 17.7% (n = 12345) had pulmonary silicosis. There were 10520 (15.1%) true positive, 1825 (2.6%) false negative, 40604 (58.2%) true negative and 16853 (24.1%) false positive pulmonary silicosis tests. Sensitivity was high (85.2%, 95% CI 84.6, 85.6) but specificity was lower (70.7%; 95% CI 70.3, 71.0). PPV was low (38.4%; 95% CI 37.9, 39.0) and NPV was high (95.7%; 95% CI 95.5, 95.9). Sensitivity increased with increasing years of employment. <h3>Conclusion</h3> Our findings support previous studies suggesting that lymph node silicosis may occur at lower RCS exposures and precedes pulmonary silicosis. The detection of lymph node silicosis in a worker serves as warning of RCS exposures and as an early indicator of potential pulmonary silicosis. However, the low PPV indicates that lymph node silicosis has limitations as a diagnostic test for pulmonary silicosis. The detection of lymph node silicosis in workers should prompt further investigations for pulmonary silicosis detection, workplace RCS exposure assessments and implementation of control and prevention measures, as appropriate.