Coal Worker's Pneumoconiosis Workup
- Author: Farhan J Khan, MD; Chief Editor: Zab Mosenifar, MD, FACP, FCCP more...
Obtain a CBC count and perform a sputum culture (as needed) to exclude infective processes.
Historically, radiographs remain the main diagnostic tool. The International Labor Organization developed a 12-point classification for standardizing the diagnosis of coal worker’s pneumoconiosis. A standard set of radiographs reflecting the amount of coal retained in the lungs is used for comparison. The scale represents a continuum of dust accumulation with nodule formation from category 0/0 to 3/4. Generally, complicated coal worker’s pneumoconiosis appears on a background of category 3 or 4 simple coal worker’s pneumoconiosis.
Simple coal worker’s pneumoconiosis usually develops as small, rounded opacities first observed mostly in the upper lobes. These densities can be classified as follows:
P - Up to 1.5 mm in diameter
Q - 1.5-3 mm in diameter
R - 3-10 mm in diameter
The lung zones are identified as follows:
RUZ and LUZ - Right upper zone and left upper zone, respectively
RMZ and LMZ - Right mid zone and left mid zone, respectively
RLZ and LLZ - Right lower zone and left lower zone, respectively
Any nodular opacity greater than 1 cm in diameter on radiographs is considered complicated coal worker’s pneumoconiosis or progressive massive fibrosis. Subcategories for this group are as follows:
A - Any opacity 1-5 cm in diameter
B - Any opacity with a diameter of 5 cm that occupies less than a third of the lung
C - One or more opacities whose diameter exceeds a third of the total area of the lung
Of note, in a small study by Reichert and Bensadoun, positron emission tomography (PET) with F-18-fluorodeoxyglucose proved to be of limited value in the evaluation of coal worker’s pneumoconiosis and associated malignancy, yielding a high rate of false-positive results.
On pulmonary function test results, persons with simple coal worker’s pneumoconiosis do not show significant impairment of lung function or a decrease ventilatory capacity. A slight decrease in the alveolar-arterial pressure gradient can be observed, along with a minor reduction in diffusing capacity (P category) and minimal hypoxemia observed in categories 2 and 3 (secondary to physiological shunting). If present, focal emphysema can result in a slight increase in compliance of the lung and an increase in residual volume.
With regard to pulmonary function tests in persons with complicated coal worker’s pneumoconiosis, abnormalities are detected in stages B and C. Ventilatory capacity is reduced in proportion to the size of the conglomerate mass. Diffusing capacity is also decreased. If the mass is large enough to destroy significant vascularity, pulmonary hypertension ensues. Additionally, hypoxemia develops earlier and more frequently in miners who smoke.
In their 4-year longitudinal study, Bourgkard et al determined that "worsening x-ray findings and pneumoconiosis were more often observed in coal miners with micronodules on CT scans, wheezing, low values of maximal midexpiratory flow (MMEF) and forced expiratory flow (FEF25-75%), and high dust exposure at first examination." This finding suggests that the presence of micronodules on CT scans, altered scores on pulmonary function tests, and wheezing signify a worse 4-year prognosis and increased risk of progression to progressive massive fibrosis. CT scanning, therefore, might be a helpful screening tool to monitor progression to pneumoconiosis.
Vallyathan et al found that "in miners without coal worker’s pneumoconiosis antioxidants, cytokine and growth factors are maintained at baseline levels present in control subjects." In contrast, miners with simple coal worker’s pneumoconiosis exhibit markedly elevated bronchoalveolar lavage fluid concentrations of antioxidants, proinflammatory cytokines, and mediators, which increase fibroblast proliferation. The inability of the lungs to maintain a balance between oxidant burden and antioxidant defenses may play a crucial role in the genesis of the disease. Increased levels of interleukins 1 and 6, tumor necrosis factor-alpha, transforming growth factor-beta1, transforming growth factor-beta2, alpha1-proteinase inhibitor, and fibronectin were found in the bronchoalveolar lavage fluid of miners with radiographically defined coal worker’s pneumoconiosis.
The 6-minute walk test (6MWT), a simple to perform test can be done as an ancillary test to help quantify possible impairment due to CWP in addition to chest imaging and pulmonary function testing.
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