Carbon monoxide and nitric oxide diffusion capacity of formerly exposed asbestos workers with high-resolution computed tomography in a cross-sectional study

Asbestos exposure can induce pulmonary fibrosis known as asbestosis, and pleural thickening, as well as various cancers. Although lung diffusion capacity (DL) including nitric oxide (NO) is assumed to be more sensitive than carbon monoxide (CO), its added value in assessment of pneumoconiosis has not been investigated yet. 371 formerly exposed workers visiting the outpatient clinic for assessment including pulmonary function testing with DL and low-dose high resolution computed tomography between 2018 and 2021 were included. Subgroups were formed depending on findings in low-dose high resolution computed tomography classified according to ICOERD. Receiver operating characteristic curve (ROC) analysis revealed some diagnostic accuracy for DLNO (AUC = 0.73; 95% confidence interval 0.64-0.82) and DLCO (AUC = 0.70; 95% confidence interval 0.60-0.79) regarding asbestosis, but not per unit alveolar volume. DLCO and DLNO correlated strongly with a decreasing score of irregular opacities according to ICOERD (ρ = - 0.87, ρ = - 0.85) but DLNO was also susceptible to emphysema. Although tendencies of a more sensitive detection of diffusion capacity impairment were observed, DLNO was not clearly superior to DLCO in assessment of asbestosis. Based on our findings and considering the lack of availability of DLNO in clinical routine, DLNO does not seem to have added value for clinical assessment of formerly asbestos exposed workers. Future studies should further investigate DLNO including healthy controls and confounders such as emphysema and smoking.