News Author: Laurie Barclay, MD
CME Author: Désirée Lie, MD, MSEd

Sept. 16, 2004 — The American Thoracic Society (ATS) updated the 1986 criteria for diagnosing and treating patients with nonmalignant disease related to asbestos, according to a report in the Sept. 15 issue of the American Journal of Respiratory and Critical Care Medicine. These conditions include asbestosis, pleural thickening or asbestos-related pleural fibrosis (plaques or diffuse fibrosis), "benign" (nonmalignant) pleural effusion, and airflow obstruction.

"Asbestos has been the largest single cause of occupational cancer in the United States and a significant cause of disease and disability from nonmalignant disease," write Tee L. Guidotti, MD, MPH, from George Washington University Medical Center in Washington, D.C., and colleagues. "To this demonstrable burden of asbestos-related disease is added the burden of public concern and fear regarding risk after minimal exposure."

The purpose of these guidelines is to assist the physician in arriving at a specific diagnosis leading to an individual treatment plan. Although subclinical disease may not be sufficiently advanced to be detected on histology, imaging, or functional studies, the association of nonmalignant disease with risk of malignancy warrants careful attention to diagnosis and monitoring for development of malignant disease, particularly lung cancer and pleural or peritoneal mesothelioma. However, most patients with nonmalignant asbestos-related disease do not develop cancer.

On Dec. 12, 2003, the ATS Board of Directors adopted this official statement covering diagnostic criteria and guidelines for documenting asbestos as a hazard, asbestos in lung tissue, clinical evaluation and indicator symptoms, occupational and environmental history, physical examination, conventional imaging, computed tomography (CT), bronchoalveolar (BAL) lavage, pulmonary function tests (PFT), disease outcomes, asbestosis, pleural abnormalities, chronic airway obstruction, implications of diagnosis for patient treatment, and actions required before the appearance of disease and after diagnosis.

As stated in 1986, the diagnosis of nonmalignant asbestos-related disease should be based on the essential criteria of a compatible structural lesion, evidence of exposure, and elimination of other plausible conditions.

Each of these criteria may be met by one of several findings or tests, including future testing modalities if and when they are validated. Because high-resolution CT (HRCT) has greatly increased the sensitivity of detection, it has recently become a standard imaging procedure. Evidence for exposure is still based on the occupational history, the demonstration of asbestos fibers or bodies, or pleural plaques. Conditions in the differential diagnosis are better understood than previously, such as idiopathic pulmonary fibrosis, or less common, such as tuberculosis, facilitating diagnosis.

If the three criteria described above suggest asbestos-related disease, there is also an additional requirement for functional impairment assessment, which is largely unchanged from 1986. This assessment should rate the impairment based on ATS criteria incorporated into the American Medical Association guides.

After diagnosing nonmalignant asbestos-related disease, the authors recommend notifying the patient, informing him or her of work-related illness and compensation options, and reporting occupational disease to the appropriate authority, as required by law.

Tertiary prevention should include smoking cessation, withdrawal from further excessive asbestos exposure, immunization against pneumococcal pneumonia and influenza, and management of concurrent respiratory and other diseases.

For optimal monitoring, patients should have a chest film and PFTs every three to five years, periodic screening for colon cancer, and observation and elevated index of suspicion, but not screening for lung cancer, mesothelioma, and gastrointestinal cancers other than colon cancer. Symptomatic disease mandates development of a patient-specific treatment plan.

"These criteria and the guidelines that support them are compatible with the Helsinki criteria, developed by an expert group in 1997, which represents substantial consensus worldwide," the authors write. "The guidelines supporting these criteria will undoubtedly change again in future, but the present guidelines should provide a reliable basis for clinical diagnosis for some years to come."

Am J Respir Crit Care Med. 2004;170:691-715

Learning Objectives for This Educational Activity

Upon completion of this activity, participants will be able to:

• List the possible manifestations of nonmalignant diseases related to asbestos.
• Describe the 2004 updates to the 1986 diagnostic criteria for asbestos-related nonmalignant diseases created by the ATS.

Clinical Context

Asbestos is the single largest cause of occupational cancer in the U.S. and a significant cause of disability from nonmalignant disease. Asbestos is a commercial industrial term that refers to hair-like long fibers of certain minerals, including chrysotile, crocidolite, and amosite asbestos. It is still a hazard for 1.3 million U.S. workers involved in building maintenance and was a hazard, until recently, for those working with brake linings, flooring, cement, paint, textiles, and insulation.

Nonmalignant diseases related to asbestos exposure include asbestosis, pleural thickening or fibrosis, benign pleural effusion, and airflow obstruction. Asbestosis is pulmonary parenchymal fibrosis with or without pleural thickening, developing many years after asbestos exposure. For example, 20 years after cessation of exposure, a prevalence of 20% of parenchymal opacities was documented with intense exposures as short as one month, as reported by Ehrlich and colleagues in the April 1992 issue of the British Journal of Industrial Medicine. Asbestosis tends to occur in the lower lung fields and is associated with restrictive impairment.

This statement from the ATS updates 1986 guidelines for the diagnosis and initial management of asbestos-related nonmalignant disease.

Study Highlights

• Demonstration of functional impairment is not required for the diagnosis of nonmalignant asbestos-related disease.
• Identification of asbestos fibers in lung tissue is not required for diagnosis because a systematic analysis for asbestos fibers is not generally available. Light microscopy is inadequate and scanning-transmission electron microscopy is usually needed.
• Asbestos bodies can be identified and quantified in lung tissue and BAL specimens. Transbronchial lung biopsy is less reliable compared with BAL or open lung biopsy.
• Nonmalignant diseases presenting similarly to asbestos-related disease should be ruled out in the workup.
• Symptomatic assessment includes history of insidious onset of dypsnea, nonproductive cough, positive ATS-DLD-78A ATS respiratory questionnaire, which predict diminished ventilatory capacity.
• Persistence of new-onset respiratory symptoms is correlated with accelerated loss of lung function and predicts future risk.
• Exposure history is usually more than 15 years before presentation. Diagnosis is based on duration, intensity, time of symptom onset, and setting of exposure. Short heavy exposures of one month to a year can result in asbestosis.
• Pertinent physical examination findings are basilar rales characterized by end-inspiratory crackles.
• The plain chest x-ray using the International Classification of Radiographs for Pneumoconiosis (or International Labor Organization [ILO] classification) is useful for diagnosis of asbestosis and asbestos-related pleural disease. The ILO profusion score correlates with mortality risk, reduced diffusion capacity, and diminished ventilatory capacity.
• Conventional CT is now replaced by HRCT at 2-cm intervals for evaluation because it is more sensitive for detecting parenchymal disease.
• The extent of asbestos plaque formation does not correlate with cumulative asbestos exposure and cannot be used to estimate exposure.
• If sputum analysis is negative, asbestos bodies in BAL may be needed to document exposure. In the absence of asbestosis, the presence of asbestos bodies indicates exposure, not disease.
• Lung function tests should include spirometry with flow-volume loop documented. The tests should discriminate between restrictive, obstructive, and mixed impairment. Restrictive impairment is most common and can occur with pleural disease. Isolated obstructive impairment is unusual.
• Exercise testing is generally not required.
• The College of American Pathologists recommends a histologic grading system based on alveolar involvement, ranging from mildest (grade I) to most severe (grade IV). Extent of disease is graded from A to C (or I to III) based on number or proportion of bronchioles involved.
• Asbestosis is more prevalent and more advanced in cigarette smokers (current and former) because of reduced clearance of asbestos from lung. Smoking does not affect the presentation of asbestos-related pleural fibrosis.
• Regression of asbestosis is rare and progression is more common.
• Pleural thickening is determined by duration from first exposure, and the International Classification of Radiographs for Pneumoconiosis provides classification for thickening based on indices of exposure and lung function measures.
• The plain chest x-ray is sensitive for locating plaques, whereas HRCT is not a practical screening method. Plaques are associated with significant reduction in lung function averaging 5% forced vital capacity even when interstitial fibrosis is absent.
• Slow progression of plaques is typical, and they are associated with greater risk of mesothelioma due to greater exposure burden rather than malignant degeneration.

Pearls for Practice

• Nonmalignant asbestos-related diseases include asbestosis, pleural thickening and plaques, pleural effusion, and airflow obstruction, all of which contribute to early disability and mortality.
• Essential diagnostic criteria include a compatible structural lesion, evidence of exposure, and exclusion of other plausible causes. HRCT has increased the sensitivity of detection and is a standard method of imaging for asbestosis

*** POSTED SEPTEMBER 22, 2004 ***