Screening for Tuberculosis and Tuberculous Infection in High-Risk Populations Recommendations of the Advisory Committee for Elimination of Tuberculosis
Screening high-risk populations for tuberculosis and tuberculous infection and providing appropriate treatment are crucial to achieving the nation's goal of eliminating tuberculosis by the year 2010 (1).
Tuberculosis is caused by bacteria (Mycobacterium tuberculosis complex, which includes M. tuberculosis, M. bovis, and M. africanum) that are transmitted from an infectious source to susceptible persons primarily through the air (e.g., through coughing). Most individuals who become infected do not experience clinical illness; infected individuals are usually asymptomatic and noninfectious. The only evidence of infection may be a reaction to a tuberculin skin test. Infection can persist for years, however, and infected persons remain at risk of contracting clinically apparent disease, especially if the immune system becomes impaired.
Investigators have estimated that greater than 90% of persons reported to have clinically apparent disease are those who have harbored tuberculosis (TB) infection for at least a year or more; the remaining 10% have an immediate progression of a recently acquired infection (CDC, unpublished data). The number of persons with latent infection in the United States is estimated to range from 10 million to 15 million (CDC, unpublished data).
Certain groups may have a higher incidence of tuberculosis than the general population because 1) the group may have a higher prevalence of infection or 2) the group may have a higher risk of disease for any given prevalence of infection. Screening and preventive therapy programs should be particularly effective for persons in these groups. This document describes these high-risk groups and provides recommendations for screening them for tuberculosis and tuberculous infection. HIGH-RISK GROUPS
On the basis of published reports in the medical literature and CDC surveillance data, the Advisory Committee for Elimination of Tuberculosis (ACET) recommends that the following groups be screened for tuberculosis and tuberculous infection.
priority groups for screening. The changing epidemiology of tuberculosis is such that groups that are now high priority may decline in risk over time, and groups not now identified to be high priority may subsequently be identified at risk. Local public health officials should identify groups of persons in the community among whom tuberculosis and transmission of infection occur. This will require collecting and analyzing data (e.g., residence, occupation, and indicators of socioeconomic status) on newly reported cases that are not now routinely collected and/or analyzed. These data will enable health departments to target screening and treatment programs to locally defined high-risk populations and areas.
Responsibility for conducting screening will vary, depending upon local circumstances. For some groups, the local health department should assume responsibility for conducting the screening. For others, the health department should alert other appropriate officials (e.g., hospital infection control officers, employers, shelter operators) of the need for screening and should offer to assist in training and evaluation. GENERAL COMMENTS ON SCREENING
Screening is done to identify infected persons at high risk of disease who would benefit from preventive therapy, and to find persons with clinical disease in need of treatment. Therefore, appropriate follow-up, after initial screening, is essential. In addition, screening programs provide 1) epidemiologic data for assessing the extent of the tuberculosis problem and its trends, 2) data for assessing the value of continued screening, and 3) the opportunity to educate the public about tuberculosis.
To the extent possible, members of high-risk groups and their health-care providers should be involved in the design, implementation, and promotion of screening programs. Implementation may be enhanced by using health department or other staff (including volunteers) who have linguistic and cultural familiarity with the population at risk. Screening Methods
A detailed discussion of current screening methods for tuberculous infection and tuberculosis can be found in the American Thoracic Society/CDC publication "Diagnostic Standards and Classification of Tuberculosis" (2).
Tuberculin skin testing is the standard method of identifying persons infected with M. tuberculosis. The intracutaneous administration of 5 units of purified protein derivative (PPD) tuberculin (Mantoux test) is the best means of detecting infection, although multiple-puncture devices may be used for screening large, low-risk populations.
Chest radiography or sputum smear examinations are the screening methods of choice only when the objective is intended to identify persons with current pulmonary disease and when the administration of preventive therapy to infected persons is not possible (e.g., among the homeless). In all screening programs, patients with signs and/or symptoms suggesting pulmonary or pleural tuberculosis should have a standard posterior-anterior chest radiograph, regardless of the tuberculin skin test result. Radiographic abnormalities suggestive of tuberculosis have been described in medical literature; however, tuberculosis may produce almost any form of pulmonary radiographic abnormality, especially in immunosuppressed persons (2). RECOMMENDATIONS FOR SPECIFIC HIGH-RISK GROUPS Persons with HIV Infection and Intravenous Drug Users
Recommendations for screening individuals with HIV infection and intravenous drug abusers to determine the presence of tuberculous infection have been published (3).
Tuberculin testing for persons with HIV infection should be conducted at the following sites:
Administrators of these facilities should ensure that the recommended screening is completed. Contacts of Infectious Cases
Because close contacts of persons with tuberculosis are at extremely high risk of infection and disease, they should be identified within 3 days and examined within 7 days after the infectious index case has been diagnosed. Comprehensive guidelines for identifying, examining, and managing contacts of persons with infectious tuberculosis have been published (4). State and local health departments are responsible for ensuring that these monitoring activities are completed. Persons with Other Medical Risk Factors
Health-care providers should tuberculin test all patients with medical risk factors that substantially increase the risk of tuberculosis. These medical risk factors include:
In addition, persons with an abnormal chest radiograph an abnormal chest radiograph that shows fibrotic lesions consistent with old healed tuberculosis should be skin tested. Medically Underserved Low-Income Populations
The incidence of tuberculosis is closely related to socioeconomic status, with the highest rates occurring among persons in low-income groups (5). Special control strategies formulated in consultation with, and targeted toward, these low-income groups and their service providers (e.g., health, welfare, and housing) are needed.
Tuberculosis prevention and control efforts among lower socioeconomic groups present special problems because these groups usually have less access to care, have less formal education, are more likely to have coexisting diseases, lack shelter or transportation, have higher rates of substance abuse, and experience more obstacles in complying with medical recommendations. Nevertheless, screening programs have demonstrated success in reaching these groups. These programs have been conducted among welfare recipients in New York City (6) and among the urban poor in Vancouver, British Columbia (7).
Tuberculosis screening recommendations for the homeless have been published (8). For these persons, screening consists of a chest radiograph (and possibly a sputum smear) to determine current disease. Tuberculin skin testing programs that identify infected persons without current disease should be undertaken only if the group is stable (i.e., the diagnostic evaluation can be completed and a course of prescribed therapy can be initiated). In most circumstances, the local government or an agency funded by the government must assume responsibility for conducting these screening programs.
Low-income groups may also be identified through occupational screening programs. These programs may be voluntary or mandated by law or regulation. Unskilled laborers, migrant farm workers, and lower paid health-care workers are occupational groups that include a large percentage of low-income persons.
Food handlers may also be an important group to screen for tuberculosis. Such screening is not done to protect customers of food establishments since M. tuberculosis is not transmitted through contaminated food and is unlikely to be spread in food establishments. However, many food handlers are from medically underserved low-income populations and/or foreign-born persons from countries with a high prevalence of tuberculosis (9).
Screening for tuberculous infection among various occupational groups can be done upon employment at the worksite or at other community sites. Screening migrant farm workers for tuberculous infection is best done near home sites rather than at temporary work locations so that preventive therapy can be more easily completed by those found to be infected. The Foreign-Born
Tuberculosis is a problem among persons who come to the United States from high-prevalence countries. (Most countries in Africa, Asia, and Latin America are high-prevalence countries.) Foreign-born persons at risk include not only immigrants (legal and illegal) and refugees but also workers and students. Because disease rates among the foreign-born are highest in the first few years after arrival in the United States, a special effort should be made to screen new immigrants (10). Children and Adolescents
Children and adolescents who are infected with M. tuberculosis are more likely to have been recently infected and, therefore, are at high risk of disease. If clinical tuberculosis develops, a serious form (e.g., meningitis or miliary disease) is more likely to occur. Furthermore, tuberculin-positive children and adolescents, with their long life expectancy, have a high cumulative risk of developing tuberculosis sometime during their lifetime. The recommended frequency of tuberculin skin testing depends upon the risk of new infection. However, annual testing is generally recommended for children in high-risk populations, such as the foreign-born and low-income groups. Screening in Other High-Risk Environments
High-risk environments are settings in which persons with infectious tuberculosis are more likely to live, the environmental characteristics (e.g., size, type of ventilation) are conducive to transmission, and large numbers of susceptible persons may be located. These environments include prisons and jails (11), nursing homes/facilities and other long-term facilities for the elderly (12), and health-care facilities (including residential mental health facilities) (13). Persons who work in these settings must be educated about the risk of transmission, the signs and symptoms of tuberculosis, and the proper procedures for minimizing the risk of transmission. Prisons and jails
Recommendations for screening, treatment, and prevention in correctional facilities have been published (11). Routine tuberculin skin testing of inmates on admission to prisons should be mandatory. Persons with symptoms compatible with pulmonary tuberculosis must have sputum and chest radiographic examinations regardless of skin-test results.
Prison authorities have primary responsibility for implementing these programs, but health departments can and should play an important advisory and regulatory role. Health departments should routinely monitor and evaluate tuberculosis control activities in prisons. Nursing homes/facilities for the elderly
Among all racial and ethnic groups and both sexes, tuberculosis case rates increase with increasing age. Nursing home residents have an incidence of disease from two to seven times higher than demographically similar persons living in other settings. Recent studies have documented unsuspected transmission of tuberculous infection in nursing homes/facilities that presents a risk to workers as well as to residents (12). Health-care facilities
The risk to hospital workers, other institutional health-care workers, and home health-care workers is lower today than in the prechemotherapy era. The principal contributors to reducing infectiousness are a lower incidence of tuberculosis in the population and the potency of modern chemotherapy regimens. However, the risk to health-care workers may still be substantial. The main risk is exposure to patients with unsuspected tuberculosis. This poses a particular problem when the clinical presentation is atypical, as is often the case when elderly patients or patients with HIV infection are involved. Procedures that induce coughing, such as sputum induction and aerosolized pentamidine treatments, may present a particular hazard to health-care workers (3).
Tuberculin skin testing upon employment should be mandatory for all persons who work in these environments. Health administrators and infection control departments in hospitals are responsible for ensuring that these recommendations are implemented. Repeat screening of persons in risk groups
The need for repeat skin testing should be determined by the likelihood of exposure to infectious tuberculosis. All tuberculin-negative individuals in high-risk groups should be retested if exposure to an infectious case occurs. In some institutional and group-living environments (e.g., hospitals, prisons, nursing homes, shelters for the homeless), the risk of exposure is probably high enough to justify repeat testing at 6- to 24-month intervals. Local health officials should make these decisions by using locally generated data. ROLE OF HEALTH DEPARTMENTS
Health departments should identify and establish working relationships with persons providing health-care services to high-risk populations and should assist them in developing and instituting screening programs appropriate for the situation. Specifically, health departments should:
Assist in training staff to perform, read, and record tuberculin skin tests; to evaluate positive tuberculin reactors for clinical tuberculosis and preventive therapy; to provide preventive therapy and monitor for compliance and adverse drug reactions; and to educate clients regarding the need for preventive therapy. The health department or facility may wish to certify staff who complete this training.
Identify medical consultants who can assist with diagnosing and managing tuberculosis cases and suspects and, as needed, managing persons on preventive therapy.
Assist with arrangements, upon request, for referring and following persons on preventive therapy who develop clinical tuberculosis or adverse drug reactions.
Assist in evaluating screening programs. Recommend continuation or discontinuation of screening programs on the basis of their effectiveness.
Review surveillance data to identify additional population subgroups for whom screening programs should be developed.
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2. American Thoracic Society/CDC. Diagnostic standards and classification of tuberculosis. Am Rev Respir Dis (in press).
3. CDC. Tuberculosis and human immunodeficiency virus infection: recommendations of the Advisory Committee for the Elimination of Tuberculosis. MMWR 1989;38:236-50.
4. American Thoracic Society/CDC. Control of tuberculosis. Am Rev Respir Dis 1983;128:336-42.
5. Hinman AR, Judd JM, Kolnik JP, Daitch PB. Changing risks in tuberculosis. Am J Epidemiol 1976;103:486-97.
6. Friedman LN, Sullivan GM, Bevilaqua RP, Loscos R. Tuberculosis screening in alcoholics and drug addicts. Am Rev Respir Dis 1987;136:1188-92.
7. Grzybowski S, Allen EA, Black WA, Chao CW, Enarson DA, Isaac-Renton JL, Peck SHS, Xie HJ. Inner-city survey for tuberculosis: evaluation of diagnostic methods. Am Rev Respir Dis 1987;135:1311-5.
8. CDC. Tuberculosis control among homeless populations. MMWR 1987;36:257-60.
9. Judson FN, Sbarbaro JA, Tapy JM, Cohn DL. Tuberculosis screening: evaluation of a food handlers' program. Chest 1983;83:879-82. 10. Rieder HL, Cauthen GM, Kelly GD, Bloch AB, Snider DE. Tuberculosis in the United States. JAMA 1989;262:385-9. 11. CDC. Prevention and control of tuberculosis in correctional institutions: recommendations of the Advisory Committee for the Elimination of Tuberculosis. MMWR 1989;38:313-20,25. 12. Stead WW, Lofgren JP, Warren E, Thomas C. Tuberculosis as an endemic and nosocomial infection among the elderly in nursing homes. N Engl J Med 1985;312:1483-7. 13. Patterson WB, Craven DE, Schwartz DA, Nardell EA, Kasmer J, Noble J. Occupational hazards to hospital personnel. Ann Intern Med 1985;102:658-80.
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