Lab Work for Asbestos Exposure
For individuals with suspected asbestos exposure, the essential "lab work" consists of pulmonary function testing (spirometry with flow-volume loop, all lung volumes, and carbon monoxide diffusing capacity) rather than traditional blood or fluid laboratory tests. 1 Imaging studies—particularly chest radiography initially, followed by high-resolution CT when indicated—serve as the primary diagnostic modalities, with bronchoalveolar lavage reserved for rare cases requiring documentation of fiber burden. 1
Initial Diagnostic Approach
Pulmonary Function Testing (Required for All Suspected Cases)
Complete pulmonary function testing should include: 1
- Spirometry with hard copy flow-volume loop for permanent medical records 1
- All lung volumes to detect restrictive patterns 1
- Carbon monoxide diffusing capacity (DLCO), which is commonly reduced and often the most sensitive indicator of early asbestosis, though relatively nonspecific 1
The classic finding in asbestosis is restrictive impairment, though mixed restrictive-obstructive patterns are frequently seen. 1 Care must be taken to discriminate effects from asbestosis versus COPD versus obesity-related restriction. 1
Imaging Studies (Primary Diagnostic Modality)
Chest radiography serves as the initial imaging study for all asbestos-exposed individuals, providing inexpensive and rapid assessment of pleural and parenchymal abnormalities. 2 However, chest radiographs lack sensitivity for early disease detection. 1
High-resolution CT (HRCT) should be obtained when: 1
- Chest radiographic findings are equivocal 1
- Experienced readers disagree about plain film abnormalities 1
- Diminished pulmonary function exists with otherwise normal chest radiographs 1
- Extensive pleural abnormalities obscure parenchymal interpretation 1
HRCT is substantially more sensitive than chest radiography for detecting both parenchymal fibrosis and pleural disease. 1 Among asbestos-exposed individuals with unremarkable chest radiographs (ILO score 0/0 or 0/1), 34% were identified by HRCT as having findings suggestive of asbestosis, with correlating decrements in pulmonary function. 1
Technical specifications for HRCT: 1
- Obtain images at 2-cm intervals 1
- Always include prone views to distinguish dependent atelectasis from true parenchymal fibrosis 1
- Look for bilateral findings including intralobular interstitial thickening, subpleural opacities, parenchymal bands, and honeycombing in advanced disease 1
Bronchoalveolar Lavage (Rarely Indicated)
BAL should be performed only in rare cases where diagnosis hinges on demonstrating asbestos bodies and fibers to document exposure, and only after negative sputum analysis. 1 Sputum analyses miss almost half of occupationally exposed individuals who have positive BAL findings. 1
Interpretation of BAL Results
Asbestos body counts correlate with exposure severity: 1
- >1 AB/ml indicates high probability of substantial occupational exposure 1
- >100 AB/ml: 60% have asbestosis; others have pleural plaques, mesothelioma, or lung cancer 1
- Log mean values by diagnosis: 1
- Asbestosis: 120 AB/ml
- Pleural plaques: 5 AB/ml
- Mesothelioma or lung cancer: 8 AB/ml
- Exposed with normal chest X-ray: 4 AB/ml
Fiber analysis by electron microscopy can be performed on BAL cells digested with bleach, with fibers expressed per 10 alveolar macrophages. 1 Amphibole fiber recovery correlates well with lung burden, but chrysotile does not due to translocation and dissolution. 1
Common Pitfalls to Avoid
Do not rely on chest radiography alone for screening or early detection—it lacks sensitivity, particularly for early interstitial disease. 1 The American College of Chest Physicians consensus found that chest radiographs are not a sensitive method for diagnosing asbestos-related interstitial disease. 1
Do not confuse pleural plaques with indicators of exposure severity—plaque extent does not correlate with cumulative asbestos exposure and cannot estimate exposure levels. 1
Do not overlook the need for prone HRCT views—failure to obtain these can result in misinterpreting dependent atelectasis as parenchymal fibrosis. 1
Do not order BAL routinely—it is reserved for rare diagnostic dilemmas where fiber documentation is essential and should only follow negative sputum analysis. 1
Surveillance Timing
Begin monitoring when time since initial exposure reaches 10 years, with chest films and pulmonary function studies every 3-5 years. 3 Asbestosis typically becomes evident only after an appreciable latency period, often two decades under current exposure conditions. 3