Relations between vital capacity, CO diffusion capacity and computed tomographic findings of former asbestos-exposed patients: a cross-sectional study

Abstract

Background: Asbestos-related lung diseases are one of the leading diagnoses of the recognized occupational diseases in Germany, both in terms of their number and their socioeconomic costs. The aim of this study was to determine whether pulmonary function testing (spirometry and CO diffusion measurement (D LCO)) and computed tomography of the thorax (TCT) are relevant for the early detection of asbestos-related pleural and pulmonary fibrosis and the assessment of the functional deficiency. Methods: The records of 111 formerly asbestos-exposed workers who had been examined at the Institute for Occupational and Maritime Medicine, Hamburg, Germany, with data on spirometry, D LCO and TCT were reviewed. Workers with substantial comorbidities (cardiac, malignant, silicosis) and/or pulmonary emphysema (pulmonary hyperinflation and/or TCT findings), which, like asbestosis, can lead to a diffusion disorder were excluded. The remaining data of 41 male workers (mean 69.8 years ±6.9) were evaluated. The TCT changes were coded according to the International Classification of High-resolution Computed Tomography for Occupational and Environmental Respiratory Diseases (ICOERD) by radiologists and ICOERD-scores for pleural and pulmonary changes were determined. Correlations (ρ), Cohens κ and accuracy were calculated. Results: In all 41 males the vital capacity (VC in % of the predicted value (% pred.)) showed only minor limitations (mean 96.5 ± 18.0%). The D LCO (in % pred.) was slightly reduced (mean 76.4 ± 16.6%; median 80.1%); the alveolar volume related value (D LCO /VA) was within reference value (mean 102 ± 22%). In the TCT of 27 workers pleural asbestos-related findings were diagnosed whereof 24 were classified as pulmonary fibrosis (only one case with honey-combing). Statistical analysis provided low correlations of VC (ρ = − 0.12) and moderate correlations of D LCO (− 0.25) with pleural plaque extension. The ICOERD-score for pulmonary fibrosis correlated low with VC (0.10) and moderate with D LCO (− 0.23); D LCO had the highest accuracy with 73.2% and Cohens κ with 0.45. D LCO /VA showed no correlations to the ICOERD-score. The newly developed score, which takes into account the diffuse pleural thickening, shows a moderate correlation with the D LCO (ρ = − 0.35, p < 0.05).

Restrictions of VC and DLCO in relation to asbestos-related computed tomographic findings quantified by ICOERD-based parameters

“…The relevant scores for the presence of asbestos-typical findings, as also confirmed in previous studies, are the scores for irregular/linear opacities (fibrosis score, Score A) and pleural plaques (pleural plaques score, Score B) [ 10 ]. In addition to the categories described, it is possible for the evaluator to mark additional pathological findings on the ICOERD sheet.…”

“…The number of pack-years ranges from 0 to 71 (median 34 years). The dose of asbestos exposure was not recorded because previous studies have not found a relationship between exposure duration and lung function values or only rough dose–response relationships [ 10 , 32 ]. The evaluation of occupational histories reveals that patients were exposed to asbestos in 22 different occupations.…”

“…Therefore, it is postulated that in all subgroups, asbestos-related changes contribute to the limitations of D LCO , which is reflected in the negative correlation of D LCO with Score C in the overall collective. A previous study, which excluded patients with concomitant diseases such as emphysema or heart failure, detected a significant reduction in D LCO associated with inhalation of asbestos fibre dust [ 10 ].…”

“…For this purpose, subjects were classified as healthy or diseased according to radiological signs of pulmonary fibrosis or pleural plaques in CT. Findings with an ICOERD Score A ≥ 2 were considered fibrosis, and the presence of pleural plaques was considered confirmed with a Score B ≥ 1 [ 10 ]. Pulmonary function values were assessed according to exceeding or falling below the LLN (lower limit of normal).…”

“…The measurement of diffusion capacity (D LCO ) is also suitable for the early recognition of changes detectable in HR-TCT after exposure to asbestos. D LCO is a sensitive parameter for detecting asbestos-related fibrosis, whereas the transfer coefficient D LCO /VA (Krogh factor, KCO) is less informative [ 10 , 11 ]. In addition to pulmonary fibrosis and pleural plaques, other radiologic changes of the subpleural lung parenchyma, such as SC, PB, or RA, may also be associated with pulmonary function restrictions [ 10 ].…”