X-ray
In the early stages, it is difficult to make a radiological diagnosis, as the pleura is often only visible with milky diffuse thickening. As soon as the plaques have reached a size of at least 5 mm, they can be visualized radiologically. Calcifications in the plaques are generally easier to visualize.
Along the parietal pleura, plaques can be detected by calcifications, especially in the area of the lower lung fields, the diaphragm and the mediastinum. Their distribution is irregular and can be unilateral or bilateral.
Changes in the area of the diaphragm are characteristic. However, the sinus is never affected.
The sensitivity of the conventional X-ray image is, however, quite low (approx. 28 %). The specificity is significantly higher at 80 % to 100 %. False-positive results were found in 20 %, because radiologically plaques are not so easily distinguished from subpleural fat deposits.
HRCT
The HRCT (High-Resolution-CT) is the most sensitive examination method for the detection of plaques. It also allows the differentiation between plaques and subpleural fat accumulation.
Lung function
In the lung function, a slight reduction of the vital capacity is usually observed.
Disturbances of gas exchange and diffusion capacity are not found.
Laboratory
The usual laboratory values show no abnormalities, in particular no signs of inflammation. Occasionally there is a reduced activity of T-lymphocytes and an increase in antinuclear antibodies (ANA).
Thoracoscopy
It is by far the most sensitive of all examination techniques. However, the indication for thoracoscopy should only be given if the diagnosis remains unclear despite the exhaustion of all non-invasive methods.
It is not at all uncommon for pleural plaques to be a chance finding during a thoracoscopy performed for other reasons.
Lavage
In the lavage, asbestos corpuscles are found in 50 % of the plaque-bearing bodies. However, these are not present in such high concentrations as in pulmonary asbestosis.