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The Selection of Patients For X-ray Examinations:
Chest X-Ray Screening Examinations
WHO Collaborating Centers for:
More than one hundred years after the discovery of the tubercle bacillus by Robert Koch, tuberculosis is still a major disease in the world. But in the United States, cases and case rates have declined. New cases continue to be found, but most often in urban areas, with increasing numbers prevalent among recent immigrants.
Until 1972, the use of diagnostic x-ray screening was the unquestioned detection tool for the diagnosis of tuberculosis. Prior to that time, it was felt that properly conducted x-ray screening, including follow-up of the positive finding, would lead to prompt diagnosis and treatment. In New York City, for example, x-ray screening was widely conducted. The New York City Health Department code required screening of pregnant women, all persons working in maternity and newborn services, all food preparation employees, Parks Department employees, Board of Education employees, as well as persons contacting newly diagnosed tuberculosis patients. In addition, the Lung Association’s mobile buses traveled actively among communities offering free mass x-ray screening of the population. But the productivity of these examinations was later found to be extremely low. Most of the persons screened were asymptomatic and latent disease was very rarely detected.
In 1972, the Food and Drug Administration’s Bureau of Radiological Health issued a statement in cooperation with the Center for Disease Control, the American College of Chest Physicians, and the American College of Radiology recommending that community chest x-ray surveys among the general population not be used as a screening procedure for the detection of tuberculosis, other pulmonary disorders, and heart disease. The American Thoracic Society recommended that chest x-rays not be done as routine screening because the number of tuberculosis cases found is extremely small and these cases would come to medical attention by other methods (a careful history of symptoms, use of tuberculin skin test, and careful follow-up of people who have the disease). In 1974, the Ninth World Health Organization Committee on Tuberculosis concluded that radiography is an expensive screening procedure for tuberculosis, contributing only a small proportion of the cases discovered and having no significant effect on the subsequent occurrence of cases.
Part of the basis for these recommendations was the recognition that tuberculosis is a two-stage disease. The first stage consists of infection by the tubercle bacillus. This infection is a subclinical event that is contained by body defenses in approximately 90 to 95 percent of the cases. In the remaining five to ten percent, the disease may become manifest sometime during their life. The tuberculin skin test can detect tuberculosis in the preclinical stage, and then, utilizing known risk factors, therapeutic measures can be taken to protect against the development of manifest disease.
The second stage consists of clinically manifest tuberculosis, a condition that almost always is suggested by symptoms or other epidemiologic factors. The chest x-ray examination is limited in that it can only demonstrate clinically manifest tuberculosis.
Recognizing this limitation and the low prevalence of tuberculosis, the Chest X-ray Panel has recommended against routine x-ray screening for tuberculosis detection and control in five specific areas.
Chest X-Ray Examinations for Employment
Mandated chest x-ray examinations, as a condition of initial or continued employment, have not been shown to be of sufficient productivity to justify their continued use for tuberculosis detection (5).
Chest X-Ray Examinations in Long-Term Care Facilities
Because conventional tuberculin skin testing may not be a reliable screening method in older and/or chronically ill persons and because these individuals may be at high risk of having tuberculosis, the results of a recent chest x-ray examination should be obtained by the facility (10,12,13). Only if unavailable, a chest x-ray examination should be performed on admission. In the absence of clinical symptoms, repeated chest x-ray examinations have not been shown to be of sufficient clinical value or productivity to justify their continued use.
Repeated Chest X-Ray Examinations of Tuberculin Reactors
After an initial evaluation, which should include a chest x-ray examination, repeated chest x-ray examinations of individuals with significant tuberculin reactions, (without current disease), whether or not they have been treated with isoniazid, have not been shown to be of sufficient clinical value to justify their continued use (2,3).
Routine Follow-up of Tuberculosis Patients Who Have Completed Treatment
Repeated chest x-ray examinations of asymptomatic tuberculosis patients who have completed treatment have been shown to be of insufficient clinical value or productivity to justify their continued use (4,7,8,9,11).
Routine Periodic Chest X-Ray Examinations During Tuberculosis Treatment
Radiographic stability does not necessarily indicate success or failure of chemotherapy as reliably as the results of sputum smear and culture, and assessment of symptoms and clinical status (1,6). However, an occasional x-ray examination may have value in confirming bacteriologic and clinical findings and enhancing patient compliance.