Asbestos Health Effects : Clinical Evaluation

by CDC

(Page 6 of 9)

History and Physical Examination

The medical evaluation of persons exposed to asbestos should include a thorough medical and occupational history, physical examination, chest radiograph, and pulmonary function tests. The same protocol has been recommended for evaluating an asymptomatic patient with a history of asbestos exposure. If indicated, more specialized radiologic and laboratory testing such as high-resolution computerized (axial) tomography scan (HRCT), bronchoalveolar lavage (BAL), or lung biopsy might be helpful. Pertinent historical information includes the source, intensity and duration of exposure, time elapsed since first exposure, and work history of household members. Asbestos accumulates in the body, and even relatively minor exposures can be important. Workplace dust measurements or estimates, and a cumulative fiber dose, as expressed in fiber-years per cubic centimeter, are important parameters of asbestos exposure (International Expert Meeting on Asbestos, Asbestosis, and Cancer 1997). Smoking history is clearly important.

Dry bibasilar rales, auscultated in the mid-axillary line, are the most common lung findings associated with asbestosis.

The physical examination should focus primarily on the patient's lungs, and particular attention should be paid to pulmonary auscultation. Fine inspiratory rales in the posterior and posterolateral lung bases, audible on deep inspiration, might be the earliest sign of interstitial fibrosis. These basilar crackles are characteristic in their sound ("fine," "cellophane," "Velcro," or "close to the ear") and occur in a bilateral basilar distribution. There is pan-inspiratory or end-inspiratory accentuation. The basilar crackles start at the bases at the midaxillary lines, spread to the posterior bases and, as disease progresses, to higher levels up from the bases. They can be difficult to distinguish from congestive heart failure (CHF) rales, but are distinct from bronchitis. The differential diagnosis can be difficult when CHF, chronic obstructive pulmonary disease, or other chronic lung disease is present, as these may be unrelated to asbestos exposure but might present similar symptoms. Generally, a chest radiograph is more sensitive than auscultation in asbestos-related disease.

Examination should also assess stigmata of other diseases that might confound the diagnosis of asbestosis. For instance, rheumatoid arthritis is sometimes associated with interstitial fibrosis. Chest-wall configuration, evidence of thoracic surgery, and cardiac status can also alter the differential diagnosis.

Signs and Symptoms

Asbestosis

Significant clinical syndromes include asbestosis, lung cancer, and mesothelioma.

Asbestosis can manifest as pleural or parenchymal fibrosis or both. Pleural asbestosis, more properly termed "asbestos-related pleural abnormalities," is the most common finding in asbestos-induced pulmonary disease and, as described previously, involves pleural thickening, often manifested as discrete pleural plaques. Pleural plaques can be seen radiologically as bilateral images of hyalin scar formation on either the visceral or, much more commonly, the parietal pleural surfaces. The specificity of pleural plaques is low on radiographs unless the plaques are well defined. The most common differential diagnosis is subpleural fat. Well-defined asbestos-related pleural plaques on radiographs include bilateral circumscribed plaques, bilateral calcification, and diaphragmatic plaques. Pleural plaques rarely cause symptoms. Diffuse pleural fibrosis, seen as visceral pleural thickening, can be associated with mild or, rarely, moderate or severe restrictive pulmonary defects, with dyspnea and restrictive changes on pulmonary function tests. There can be a benign pleural effusion.

Progressive dyspnea on exertion is a common symptom of asbestosis.

A patient with parenchymal asbestosis commonly develops fatigue, weight loss, and insidious onset of dyspnea on exertion. As the disease progresses, the dyspnea worsens, regardless of any further asbestos exposure. A dry cough typically occurs, but a productive cough, even in a nonsmoker, is not uncommon. Patients often describe a "tight" feeling in the chest. Common findings are bibasilar fine end-inspiratory crackles (32% to 64%) and clubbing of the fingers (32% to 42%) (which occurs at a later stage of the disease). In the advanced stages of the disease, signs of cor pulmonale are common. Functional disturbances can include gas exchange abnormalities (e.g., diffusing capacity), a restrictive pattern, and obstructive features due to small airway disease (International Expert Meeting on Asbestos, Asbestosis, and Cancer 1997). The interstitial disease is radiographically demonstrated as a reticular fibrosis located predominantly in the lower lung fields. Radiologic evidence is often not present until at least 5 years after exposure. The American Thoracic Society states that there is convincing evidence that an asbestos-related pulmonary abnormality can occur in the absence of definite radiologic change (American Thoracic Society 1986). The detection of asbestosis by standard films (chest radiography) should be guided by standard reading methods such as those of the International Labour Organization (ILO) classification system and read by certified B readers trained to use this classification system. Early changes not seen on chest radiography can be found using HRCT in selected cases.

About the Author

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The Centers for Disease Control and Prevention (CDC) is one of the 13 major operating components of the Department of Health and Human Services (HHS), which is the principal agency in the United States government for protecting the health and safety of all Americans and for providing essential human services, especially for those people who are least able to help themselves.