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Screening for Tuberculosis and Tuberculosis Infection in High-Risk Populations Recommendations of the Advisory Council for the Elimination of Tuberculosis

The following CDC staff member prepared this report:

Alan B. Bloch, M.D., M.P.H. Division of Tuberculosis Elimination National Center for Prevention Services

in collaboration with the

Advisory Council for the Elimination of Tuberculosis


This report from the Advisory Council for the Elimination of Tuberculosis updates and replaces previous recommendations for screening for tuberculosis (TB) and TB infection among high-risk populations. {MMWR 1990;39(No. RR-8): 1-7}. In particular, these recommendations a) emphasize that screening for TB infection should not be given preference over higher priority TB prevention and control activities, especially identifying and completely treating all persons who have active TB as well as conducting prompt, effective contact investigation; b) provide more detailed recommendations for screening specific high-risk groups; c) provide a detailed description of the tuberculin skin test; and d) revise CDC's previous recommendations regarding anergy testing. This report is for public health policymakers, administrators, program directors and managers as well as health-care providers and others who provide care or services to persons at increased risk for TB infection and disease.


Tuberculosis (TB) is caused by bacteria (Mycobacterium tuberculosis complex, which includes M. tuberculosis, M. bovis, and M. africanum) transmitted from an infectious source to susceptible persons primarily through the air (e.g., through coughing) (1). Most infected persons do not experience clinical illness, but are usually asymptomatic and noninfectious. The only evidence of infection may be a reaction to a tuberculin skin test. However, infection can persist for years, and infected persons can remain at risk for developing clinical TB, especially if the immune system becomes impaired. The estimated number of persons having latent TB infection in the United States ranges from 10 million to 15 million (CDC, unpublished data).

Because of a higher prevalence of infection or a higher risk for disease for any given prevalence of infection among certain groups, the incidence of TB may be higher among these groups than among the total population. Screening and preventive therapy programs are important for persons in these high-risk groups.


Three basic strategies are critical to the prevention and control of TB. The first priority is identifying and completely treating all persons who have active TB (2,3). The second priority is contact investigation (i.e., finding and evaluating persons who have had contact with TB patients, determining if they have TB infection or disease, and treating them appropriately) (4). Contact investigations are important for identifying persons who have active TB and infected persons at high risk for developing TB. The third priority is screening populations at high risk for TB to locate persons infected with TB and giving complete therapy to prevent the infection from progressing to active, contagious disease (3,5). This screening also may identify cases of active disease.

Although screening high-risk populations for TB infection and providing preventive therapy are crucial to achieving the nation's goal of eliminating TB (6), completion of TB therapy and contact investigation should have priority over screening. Decisions to screen particular groups should be based on local epidemiologic data and made in consultation with local health jurisdictions to ensure appropriate follow-up, evaluation, and management of persons having TB infection or disease. Health-care agencies or other facilities should consult with the local health department before starting a skin-testing program to ensure that adequate provisions are made for the evaluation and treatment of persons whose tuberculin skin tests are positive. Tuberculin skin-testing programs that identify infected persons without current disease should be undertaken only if the diagnostic evaluation and a course of prescribed therapy can be initiated and completed.

Because most state and local TB control programs that report high TB morbidity have inadequate resources to screen all persons in high-risk groups and treat those persons who are infected, involvement of other health-care providers in screening and preventive treatment activities is important. These health-care providers can augment the limited resources of health departments by conducting appropriate screening efforts. This collaboration will necessitate additional efforts to train health-care workers in the administration, reading, and interpretation of the tuberculin skin test and in the appropriate use of preventive therapy. Priorities for screening activities should be determined by assessment of available resources and the probability of infection and disease among groups in the community.

Groups that have the highest priority in all areas of the country include contacts of persons who have suspected or confirmed TB and patients who have human immunodeficiency virus (HIV) infection or risk for HIV infection. In particular areas of the country, other groups at high risk may include persons who inject illicit drugs, persons who have certain medical risk factors, foreign-born persons recently arrived from countries with a high incidence or prevalence of TB, and residents of congregate settings where risk for transmitting M. tuberculosis is increased (e.g., correctional facilities, long-term care facilities, and homeless shelters). Screening persons in low-risk groups is not likely to be cost-effective and should be discontinued.


Based on published reports in the medical literature and CDC surveillance data, the Advisory Council for the Elimination of Tuberculosis (ACET) recommends that the following groups be screened for TB and TB infection:

  1. close contacts (i.e., those sharing the same household or other enclosed environments) of persons known or suspected to have TB;

  2. persons infected with HIV;

  3. persons who inject illicit drugs or other locally identified high-risk substance users (e.g., crack cocaine users);

  4. persons who have medical risk factors known to increase the risk for disease if infection occurs (see Persons Having Other Medical Risk Factors);

  5. residents and employees of high-risk congregate settings (e.g., correctional institutions, nursing homes, mental institutions, other long-term residential facilities, and shelters for the homeless);

  6. health-care workers who serve high-risk clients;

  7. foreign-born persons, including children, recently arrived (within 5 years) from countries that have a high TB incidence or prevalence;

  8. some medically underserved, low-income populations;

  9. high-risk racial or ethnic minority populations, as defined locally; and

  10. infants, children, and adolescents exposed to adults in high-risk categories.

    Flexibility is needed in defining high-priority groups for screening.

The changing epidemiology of TB indicates that the risk for TB among groups currently considered high priority may decrease over time, and groups currently not identified as at risk subsequently may be considered as high priority. Local public health officials should identify community groups among whom TB and transmission of infection occur. Identification of these groups requires collecting and analyzing a) data on newly reported cases available as part of TB surveillance (e.g., residence, occupation, race/ethnicity, country of origin, and status of HIV infection, injecting drug use, homelessness, and congregate settings), b) data not routinely collected and/or analyzed (e.g., indicators of socioeconomic status), and c) data from tuberculin screening programs (e.g., at correctional institutions and health-care facilities). These data will enable health departments and other local facilities to target screening and treatment programs to locally defined high-risk populations and areas.

Using surveillance information, local or state TB programs should take the lead in determining groups to be screened. Responsibility for conducting screening will vary, depending on local circumstances. For some groups, the local health department should conduct the screening. For others, the health department should discuss the need for screening with other appropriate persons (e.g., correctional facility staff, hospital infection control officers, and shelter operators) and offer assistance in training, evaluation, and, if necessary and possible, provision of supplies. In some areas, gaining the commitment of private health-care providers and community health centers to screen and provide follow-up for the high-risk patients they serve will be vital.


Screening persons other than members of high-risk groups is not recommended because screening low-risk persons diverts resources from other priority activities and because many positive tests in low-risk persons do not represent TB infection. The goal of screening programs must be clearly defined: screening is usually conducted to identify infected persons who are at high risk for disease and who would benefit from preventive therapy or to find persons who have clinical disease and need treatment. Screening programs also can provide a) epidemiologic data for assessing TB and its trends in a community, b) data for assessing the value of continued screening, and c) baseline data to help with assessment if subsequent exposure occurs (e.g., for nursing home residents and employees in some occupations). Screening programs should not be undertaken unless necessary facilities for patient evaluation and treatment are identified and made available and unless patients found to be positive are likely to complete preventive therapy.

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 (6-8). Implementation may be enhanced by using health department or other staff (including trained volunteers) who have linguistic and cultural familiarity with the population at risk.


Tuberculin skin testing is the standard method for identifying persons infected with M. tuberculosis (1). The Mantoux test (i.e., the intracutaneous administration of five units of purified protein derivative {PPD} tuberculin) best detects infection. Because they are less specific than the Mantoux test, multiple puncture devices should not be used to screen high-risk populations (9).

Screening for disease rather than infection may be more appropriate in some circumstances (e.g., when the tuberculin skin-test results may be unreliable, when administering and reading the test or following up infected persons for preventive therapy may be impractical, when the risk for disease is high, or when the consequences of an undiagnosed case may be severe). Chest radiography is the preferred screening method when the objective is to identify persons who have current pulmonary TB and when preventive therapy for infected persons is not the primary goal (e.g., in high turnover jails or in some homeless shelters). In these screening programs, patients who have signs and/or symptoms suggesting pulmonary or pleural TB (e.g., cough of >2 weeks' duration) should have a standard posterior-anterior chest radiograph, regardless of the tuberculin skin-test result. Although TB produces certain radiographic abnormalities more frequently than others, almost any form of pulmonary radiographic abnormality may result from TB, especially in immunosuppressed persons (1).


A detailed review of the tuberculin skin test has been published recently and is summarized here (10). Tuberculin skin-test results should be evaluated within the context of each patient's epidemiologic and environmental potential for infection (11).

Sensitivity, Specificity, and Positive Predictive Value of the Tuberculin Skin Test

Although the tuberculin skin test is now the only method for detecting M. tuberculosis infection, the test is neither 100% sensitive nor 100% specific. Sensitivity is a test's ability to identify correctly those persons who have a condition (e.g., those infected with M. tuberculosis). Specificity is a test's ability to identify correctly those persons who do not have a condition. In populations having a high prevalence of infection with nontuberculous mycobacteria or vaccination with Bacille Calmette-Guerin (BCG), the specificity of the tuberculin test will be low.

The positive predictive value of the tuberculin test is also variable. Positive predictive value reflects the ability of a positive test to identify those persons who have a condition (i.e., the probability that a condition is present when the test is positive). As the prevalence of TB infection in the population decreases, the positive predictive value of the tuberculin test also decreases. The prevalence of infection among the total adult population in the United States is an estimated 5%-10% (CDC, unpublished data). Among populations residing in areas where cross-reactions caused by nontuberculous mycobacteria are common, the positive predictive value of the tuberculin test is low if a cutoff of greater than or equal to 10 mm is used to define a positive test.

Interpreting Tuberculin Skin-Test Results

The criteria endorsed by the American Thoracic Society and CDC for a positive tuberculin skin-test result are intended to increase the likelihood that persons at high risk for TB will be candidates for preventive therapy and that persons having tuberculin reactions not caused by M. tuberculosis will not receive unnecessary diagnostic evaluation or treatment (1,3,4).

For those persons who have had recent close contact with a person who has active TB and for those whose chest radiographic findings suggest TB, skin-test reactions are likely to represent infection with M. tuberculosis. Persons infected with HIV may have a limited ability to respond to tuberculin, even if they are infected with tubercle bacilli. These groups are at high risk for TB. Thus, to ensure that persons infected with TB are evaluated and appropriately treated, the sensitivity provided by a greater than or equal to 5-mm cutoff for a positive test is appropriate for these groups (Table_1). Although persons having HIV infection have a decreased ability to respond to tuberculin, some severely immunosuppressed persons infected with tubercle bacilli may still manifest a positive reaction and benefit from tuberculin skin testing.

Other factors (e.g., certain medical conditions or injecting-drug use without simultaneous HIV infection) moderately increase the risk for active TB. A reaction of greater than or equal to 10 mm should be considered positive for these groups (Table_1). This cutoff is also appropriate for other groups: persons born in countries with a high prevalence or incidence of TB; medically underserved, low-income populations; residents and employees of most correctional institutions and nursing homes; health-care workers in high-risk settings (as defined in CDC guidelines); and, because of the increased risk for severe disease, children <4 years of age.

Routine screening is not recommended for populations at low risk for infection with M. tuberculosis. However, if these persons are tested, a higher cutoff of greater than or equal to 15 mm is recommended (Table_1).

False-Positive Reactions

A small percentage of tuberculin reactions may be caused by errors in administering the test or in reading results. However, false-positive results are more commonly attributable to the presence in tuberculin of antigens shared with other mycobacteria. The potential sources of cross-reactions caused by these antigens are infection with nontuberculous mycobacteria and vaccination with BCG. Distinguishing clearly between reactions caused by infection with M. tuberculosis and those caused by other mycobacteria is difficult. However, the larger the induration, the greater is the likelihood that the reaction represents infection with M. tuberculosis. Similarly, clearly distinguishing between a tuberculin skin-test reaction caused by infection with M. tuberculosis and a reaction caused by BCG vaccination is difficult. The probability that a skin-test reaction results from infection with M. tuberculosis rather than from BCG vaccination increases a) as the size of the reaction increases, b) when the patient is a contact of a person who has TB (especially if that person has infected others), c) when a family history of TB exists or when the patient's country of origin has a high incidence or prevalence of TB, and d) as the interval between vaccination and tuberculin testing increases (because vaccination-induced reactivity wanes over time and is unlikely to persist for >10 years) (12,13). A history of BCG vaccination is not a contraindication to skin testing.

False-Negative Reactions

False-negative tuberculin skin-test reactions have many potential causes (1). Nonresponsiveness to delayed-type hypersensitivity-inducing antigens like tuberculin is common among persons having impaired immunity (e.g., HIV-infected persons). Delayed-type hypersensitivity can be assessed with skin-test antigens such as tetanus toxoid, mumps, and Candida. Most healthy persons in the population are sensitized to these antigens. However, the scientific basis for anergy testing is tenuous (14). Most skin-test antigens used for anergy testing have no standardization. Thus, anergy testing is usually not part of screening for TB infection.

All HIV-infected persons should be tuberculin tested (15,16). Those who are tuberculin-positive (greater than or equal to 5 mm) should be evaluated for TB disease and placed on appropriate curative or preventive therapy. Preventive therapy should be administered to tuberculin-positive, HIV-infected persons, regardless of age. If they are at high risk for TB, persons failing to react to tuberculin may be evaluated for anergy (17), although the lack of standardization of anergy testing practices should be considered.

Booster Phenomenon and Two-Step Tuberculin Skin Testing

Periodic use of the tuberculin skin test is valuable for the surveillance of tuberculin-negative persons at risk for exposure to M. tuberculosis. Repeated testing of uninfected persons does not sensitize them to tuberculin. However, delayed-type hypersensitivity resulting from mycobacterial infection or BCG vaccination may gradually wane with years. Although subsequent initial skin testing may be negative, the stimulus of a first test may boost or increase the size of the reaction to a second test administered 1 week to 1 year later and thus may suggest an apparent -- but false -- tuberculin conversion.

Although the booster phenomenon may occur at any age, its frequency increases with age and is highest among persons >55 years of age and/or among those persons who have had prior BCG vaccination (18). When tuberculin skin testing of adults is repeated periodically, as in employee-health or institutional screening programs, an initial two-step approach can reduce the likelihood that a boosted reaction will be misinterpreted as a recent infection. If the first tuberculin test result is negative, a second 5-TU test should be administered 1 week to 3 weeks later. A positive second result probably indicates boosting from a past infection or prior BCG vaccination. Persons having a boosted reaction should be classified as reactors, not converters. If the second result is negative, the person is probably uninfected, and a positive reaction to subsequent tests indicates a true tuberculin skin-test conversion (see Definition of a Tuberculin Skin-Test Conversion).

Because of problems with continued cross-reactions with other mycobacteria, the specificity of the tuberculin test is less when serial skin testing is performed than when a single test is administered. Thus, serial skin-testing programs tend to overestimate the incidence of new TB infection in the tested population. Because of this potential for overestimation of incidence, serial skin-testing programs should be targeted to populations at high risk for continued exposure to infectious TB.

Definition of a Tuberculin Skin-Test Conversion

Recent tuberculin skin-test converters are considered at high risk. An increase in induration of greater than or equal to 10 mm within a 2-year period is classified as a conversion to a positive test among persons <35 years of age. An increase in induration of greater than or equal to 15 mm within a 2-year period is classified as a conversion for persons greater than or equal to 35 years of age. Regardless of age, for employees in facilities where a person who has TB poses a hazard to many susceptible persons (e.g., health-care facilities, schools, and child-care facilities), an increase of greater than or equal to 10 mm induration should be considered positive.

Tuberculin Testing During Pregnancy

Studies in which the same patients were tested during and after pregnancy have demonstrated that pregnancy has no effect on cutaneous tuberculin hypersensitivity. Tuberculin skin testing is considered valid and safe throughout pregnancy. No teratogenic effects of testing during pregnancy have been documented (19).


Contacts of Persons Who Have Infectious TB

Because the risk for infection and disease is particularly high among close contacts of persons having TB, these persons should be identified promptly (usually within 3 days) and examined soon (usually within 7 days) after identification of the potentially infectious patient (4,6). State and local health departments should work with local health-care providers to ensure completion of these monitoring activities. Prompt notification of state and local agencies about suspected or newly diagnosed and potentially infectious cases is critical for contact investigation.

Persons Who Have HIV Infection

HIV infection is the strongest risk factor yet identified for the development of TB disease in persons having TB infection (20-23). All HIV-infected persons should receive a PPD-tuberculin skin test (5-TU, PPD by the Mantoux method) (15,16).

Tuberculin testing for persons infected with HIV should be conducted in settings where HIV-infected persons or those at risk for HIV infection receive care. Administrators should ensure that the recommended screening is implemented and that prompt follow-up, evaluation, and treatment occurs. Because tuberculin skin-test results are less reliable as CD4 counts decline, screening should be completed as early as possible after HIV infection occurs. Those HIV-infected patients at high risk for continuing exposure to patients who have TB should be screened periodically for TB infection. If they have TB symptoms or if they are exposed to a patient who has pulmonary TB, HIV-infected persons should be evaluated promptly for TB. Because active disease can develop rapidly in HIV-infected persons, the highest priority for contact investigation should be given to persons potentially coinfected with HIV and TB.

Persons Who Inject Drugs

Because they are at high risk for TB and HIV infection, the priority for screening is high for persons who inject illicit drugs (16,20-22,24, 25). Drug treatment programs and other settings that provide care for persons who inject drugs should skin test injecting-drug users. If further evaluation and case management is necessary, adequate referral mechanisms should be in place. Coordination of these activities with local alcohol and other drug abuse treatment programs should be encouraged. Priority should be given to screening in facilities that are able to provide on-site, directly observed preventive therapy for 6-12 months to persons who have TB infection (e.g., clients of methadone maintenance treatment programs or residential treatment programs).

Persons Who Have Other Medical Risk Factors

Health-care providers should administer tuberculin tests to all patients who have medical risk factors that substantially increase the risk for TB (3,22). These patients should be screened in settings where they receive primary or subspecialty care (e.g., infectious disease, immunology, endocrinology, hematology/oncology, nephrology, rheumatology, pulmonology, and gastroenterology) or on admission to a hospital. These medical risk factors include the following:

  1. HIV infection,

  2. diabetes mellitus,

  3. conditions requiring prolonged high-dose corticosteroid therapy and other immunosuppressive therapy (including bone marrow and organ transplantation),

  4. chronic renal failure,

  5. some hematologic disorders (e.g., leukemias and lymphomas),

  6. other specific malignancies (e.g., carcinoma of the head or neck),

  7. weight of greater than or equal to 10% below ideal body weight,

  8. silicosis,

  9. gastrectomy, and

  10. jejunoileal bypass.

    In addition, persons who have an abnormal chest radiograph showing

fibrotic lesions consistent with old, healed TB should be skin tested. Regardless of age, persons who have a positive skin test and parenchymal lung scarring are at high risk for TB if they have not previously received TB treatment or preventive therapy.

Residents and Employees of High-Risk Congregate Settings

High-risk environments are settings where a) persons who have infectious TB are more likely to live, b) environmental characteristics (e.g., type of ventilation and size) are conducive to transmission, and c) many susceptible persons at risk for prolonged exposure to potentially infectious patients may be located. These environments include prisons and jails (26,27), nursing homes and other long-term facilities for the elderly (28), health-care facilities (29), homeless shelters (30), and residential settings for HIV-infected persons (31). Persons working in these settings should be educated about the risk for transmission, the signs and symptoms of TB, and proper procedures for minimizing the risk for transmitting TB infection. Clients and employees should be tuberculin tested on admission or initial employment.

Residents and Employees of Prisons and Jails

Recommendations for screening, treatment, and prevention in correctional facilities advise that on entry, all inmates should be screened for TB symptoms by a standardized interview process (26,27). Persons who have symptoms suggesting pulmonary TB should be immediately isolated and evaluated for active TB. Initial screening of inmates may vary, depending on each inmate's length of stay and on an assessment of the risk for transmission of TB infection in the facility.

In long-term facilities, tuberculin skin-test screening of all inmates without a documented positive skin-test result should be mandatory. If boosting is common among the population served by the facility, two-step skin testing should be considered. Inmates who have HIV infection and those at risk for HIV infection but whose HIV status is unknown should have a chest radiograph as part of the initial screening, regardless of skin-test results.

In short-term facilities serving high-risk populations, tuberculin skin-test screening is generally not feasible, but is recommended for inmates who will remain in custody for greater than or equal to 14 days. Inmates who have HIV infection and those at risk for HIV infection but whose HIV status is unknown should have a chest radiograph as part of initial screening, regardless of skin-test status. In some large jails, officials should consider using on-site chest radiography to screen all inmates (short-term and long-term) for TB. In short-term facilities serving low-risk populations, screening inmates may be limited to screening for symptoms, provided that arrangements are made with a collaborating facility to receive inmates exhibiting symptoms.

Tuberculin skin-test screening also should be mandatory for all correctional staff in short-term or long-term facilities. Staff should be informed that if they are immunosuppressed, they should consult a health-care provider for appropriate follow-up and screening for TB.

Medical units within correctional facilities should conduct a thorough risk assessment and follow recommendations for prevention of transmission of TB infection in health-care facilities (29). Correctional authorities have primary responsibility for implementing these programs, but health departments should assist in program planning and training as well as regulating, advising, monitoring, and evaluating TB-control activities in correctional facilities.

Residents and Employees of Nursing Homes/Facilities for the Elderly

Because TB case rates increase with age among all racial and ethnic groups and both sexes, screening for TB in facilities providing long-term care to the elderly is recommended (28). The incidence of disease is two to seven times higher among nursing home residents in some areas than among demographically similar persons in other settings. Studies indicate that unsuspected transmission of M. tuberculosis in nursing homes/facilities presents a risk to residents and workers (32,33). Residents should be screened for TB infection on admission by use of the two-step skin-testing method. Screening with chest radiographs alone is insufficient. Although few residents will be candidates for preventive therapy, baseline test results are essential to interpretation of subsequent tests if an acute exposure occurs. The two-step method also should be used for baseline screening of employees. Testing should be repeated in the event of exposure.

Residents and Workers at Homeless Shelters

Screening to find cases of active TB among the homeless consists of a chest radiograph (and possibly a sputum smear and culture) to determine current disease (30). Tuberculin skin-testing programs identifying infected persons who do not have current disease should be undertaken only if the diagnostic evaluation and course of preventive therapy can be initiated and completed. A special effort should be made to identify homeless persons coinfected with TB and HIV infection and to provide directly observed preventive therapy. Unless a shelter has its own health-care staff, the local government or a government-funded agency should assume responsibility for conducting screening programs for the homeless.

Health-Care Workers

Transmission of M. tuberculosis is a recognized risk in health-care facilities (29). Transmission is most likely to occur from patients who have unrecognized pulmonary or laryngeal TB, who are not on effective anti-TB therapy, and who have not been placed in TB isolation. Recent TB outbreaks in health-care facilities, including outbreaks of multidrug-resistant TB, have created heightened concern about nosocomial transmission. Increases of TB in some geographic areas are related to the high risk for TB among immunosuppressed persons infected with HIV. Transmission of M. tuberculosis to HIV-infected persons is of particular concern because, if infected with TB, these persons are at high risk for the rapid development of active TB. Thus, health-care facilities should be particularly alert to the need for preventing transmission of M. tuberculosis in settings where persons who have HIV infection receive care or work.

Health administrators and infection control departments in hospitals are responsible for ensuring the implementation of these recommendations. Implementing an effective TB control program requires risk assessment; early identification, isolation, and complete treatment of infectious TB patients; effective engineering controls; an appropriate respiratory protection program; and education, counseling, screening, and evaluation for health-care workers.

The Foreign-Born

TB is a problem among persons who arrive in the United States from countries having a high prevalence or incidence of TB (e.g., most countries in Africa, Asia, and Latin America) (34-37). Foreign-born persons at risk include immigrants (documented and undocumented), refugees, and some migrant workers and students. Because disease rates among the foreign-born are highest in the first few years after arrival in the United States, efforts should be made to screen new immigrants. Culturally and linguistically sensitive evaluation and treatment programs should be provided to help ensure a successful treatment outcome. Services should not be denied because of a real or perceived undocumented immigration status.

Other High-Incidence Population Groups

The incidence of TB is closely related to socioeconomic status; higher rates occur among persons in low-income groups (38). Special control strategies targeted toward these low-income groups are needed. In addition, community leaders from high-risk populations and service providers (e.g., health, welfare, and housing) for these groups should be involved in planning and implementing programs (8).

Implementation of TB prevention and control efforts among lower socioeconomic groups presents special problems because these groups usually have less access to care, are more likely to have coexisting diseases, lack adequate shelter and transportation, and encounter more obstacles to treatment and health-care delivery. However, screening programs have demonstrated success in reaching these groups (39,40).

Screening for TB infection among certain occupational groups may occur at the worksite or other community sites. Screening migrant farm workers for TB infection is best conducted near home sites rather than at temporary work locations so that preventive therapy can be completed more easily for those who are infected (41). High-risk groups also may be screened whenever they have access to health care.

Persons Who Use Alcohol and Other Noninjecting Drugs

Because many persons who use alcohol and other noninjecting drugs are members of high-risk groups (e.g., HIV-infected persons, the homeless, residents of correctional facilities, and medically underserved, low-income persons), they should be included in screening activities if they also belong to a high-risk group. Because persons who use alcohol and other noninjecting drugs may be at risk for repeated exposure to others who have TB, a risk assessment and, if necessary, screening for TB infection should be administered on admission to a treatment program and on an annual basis, unless these persons are known to be tuberculin positive. Screening is not recommended for those persons who use alcohol and other noninjecting drugs but who are not members of high-risk groups because this screening diverts resources from higher priority activities.


Although children in high-risk groups or those exposed to adults in high-risk groups may benefit from screening, most children are not members of high-risk groups. Mass or individual screening of children at low risk is not recommended because screening persons at low risk for TB infection diverts resources from higher priority activities and identifies few infected children (42,43). In addition, the reactions in low-risk children are often false-positive.

School-based screening for TB infection among children was started in the 1950s when infection and disease rates were higher than at present. The major purpose of school testing is to identify infected children who can be treated before the infection progresses to infectious TB during adolescence or adulthood. Because broad-based school testing involves screening large numbers of low-risk children and because the majority of children who have pediatric TB are preschool age, generalized school screening as a public health measure is an ineffective method of detecting or preventing cases of childhood TB and should be discontinued (43).

Well-conducted contact tracing of infectious cases and refugee or immigration testing are more efficient methods than nonselective school-based testing for detecting children who have TB infection. However, targeted testing of high-risk children should be encouraged and may be conducted in the school setting (44). Before any testing program for children is implemented, arrangements for evaluation and treatment of children who test positive should be in place.


The need for repeat skin testing should be determined by the likelihood of continued exposure to infectious TB. All tuberculin-negative persons should be retested if they are exposed to an infectious person. In some institutional and group-living environments (e.g., hospitals, prisons, nursing homes, and shelters for the homeless), the risk for exposure is enough to justify repeat testing at regular intervals. The frequency of repeat testing depends on the degree of risk for exposure, as determined by locally generated data. To assist in making these decisions, local facilities should compile and analyze their epidemiologic and programmatic data.


In conjunction with local providers serving high-risk populations, health departments should assist in the development, implementation, and evaluation of TB screening programs appropriate for their communities by participating in specific activities:

  1. Establishing priorities for prevention and control activities -- Screening for TB infection should not be given preference over higher priority activities, especially complete treatment of patients having TB or TB/HIV infection as well as prompt, effective contact investigation.

  2. Determining priorities for screening activities -- This determination should be made by evaluating available resources, the probability of infection and disease among groups in the community, and the ability to ensure that those persons infected with TB will complete preventive therapy. Groups with the highest screening priorities include contacts of persons suspected or confirmed to have TB and patients having HIV infection.

  3. Reviewing epidemiologic and programmatic data to identify additional groups for whom screening programs should be developed -- This review includes a) assessing the incidence, prevalence, and sociodemographic characteristics of persons having TB or TB infection; b) identifying high-risk groups and settings to determine whether a need for screening is indicated; c) designing tuberculin screening programs to reach the high-risk groups in communities; and d) ensuring completion of preventive therapy.

  4. Identifying and establishing working relationships with persons, facilities, and agencies providing health-care services to high-risk populations -- These service providers should be assisted in the development, implementation, and evaluation of screening programs appropriate to the needs of the community. The decision to initiate a skin testing program for a high-risk group should be based primarily on the ability of the TB control program and health-care providers to provide adequate preventive therapy services (i.e., tuberculin skin testing, reading and interpreting the tests, evaluating persons who have positive results, initiating preventive therapy when appropriate, monitoring patients for adverse reactions, and ensuring that patients complete preventive therapy). To be effective, the plan for evaluation and treatment should be developed before testing begins.

  5. Assisting health-care providers who serve high-risk groups -- These providers should be assisted in providing screening services, evaluating data from screening programs to determine program effectiveness, and recommending appropriate future screening activities.

  6. Providing support for staff training -- Staff should be trained to perform, read, and record results of tuberculin skin tests; evaluate positive-tuberculin reactors for clinical TB and preventive therapy; provide preventive therapy and monitor for adherence and adverse drug reactions; and educate clients regarding the need for preventive therapy. The health department or facility may certify staff completing this training.

  7. Identifying medical consultants having expertise in TB patient management -- These consultants should be able to assist with managing persons who have TB or are suspected to have TB, their contacts, and persons receiving preventive therapy.

  8. Arranging referrals and monitoring -- Upon request, assistance should be provided in making arrangements for referring and monitoring persons who have clinical TB or adverse drug reactions while on preventive therapy.

  9. Reviewing screening activities -- Periodic assessments of screening activities are needed to examine the effectiveness of identifying infected persons and of ensuring that these persons complete preventive therapy.

  10. Evaluating screening programs -- Regular assessments of screening programs are needed to determine their effectiveness. Recommendations for continuing or discontinuing screening programs should be made on the basis of their effectiveness.


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  2. CDC. Initial therapy for tuberculosis in the era of multidrug resistance: recommendations of the Advisory Council for the Elimination of Tuberculosis. MMWR 1993;42(No. RR-7).

  3. American Thoracic Society/CDC. Treatment of tuberculosis and tuberculosis infection in adults and children. Am J Respir Crit Care Med 1994;149:1359-74.

  4. American Thoracic Society/CDC. Control of tuberculosis in the United States. Am Rev Respir Dis 1992;146:1623-33.

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Note: To print large tables and graphs users may have to change their printer settings to landscape and use a small font size.

TABLE 1. Summary of interpretation of tuberculin skin-test results
  1. An induration of >=5 mm is classified as positive in the following:
     - Persons who have had recent close contact with persons who have ac-
       tive TB;
     - Persons who have human immunodeficiency virus (HIV) infection or
       risk factors for HIV infection but unknown HIV status;
     - Persons who have fibrotic chest radiographs consistent with healed TB.

  2. An induration of >=10 mm is classified as positive in all persons who do not
     meet any of the above criteria, but who belong to one or more of the fol-
     lowing groups having high risk for TB:
     - Injecting-drug users known to be HIV seronegative;
     - Persons who have other medical conditions that have been reported
       to increase the risk for progressing from latent TB infection to active
       TB. These medical conditions include diabetes mellitus, conditions
       requiring prolonged high-dose corticosteroid therapy and other
       immunosuppressive therapy (including bone marrow and organ trans-
       plantation), chronic renal failure, some hematologic disorders (e.g.,
       leukemias and lymphomas), other specific malignancies (e.g., carci-
       noma of the head or neck), weight loss of >= 10% below ideal body
       weight, silicosis, gastrectomy, jejunoileal bypass;
     -  Residents and employees of high-risk congregate settings: prisons and
       jails, nursing homes and other long-term facilities for the elderly,
       health-care facilities (including some residential mental health facili-
       ties), and homeless shelters;
     - Foreign-born persons recently arrived (i.e., within the last 5 years) from
       countries having a high prevalence or incidence of TB;
     - Some medically underserved, low-income populations, including mi-
       grant farm workers and homeless persons;
     - High-risk racial or ethnic minority populations, as defined locally;
     - Children <4 years of age or infants, children, and adolescents exposed
       to adults in high-risk categories.

  3. An induration of >=15 mm is classified as positive in persons who do not
     meet any of the above criteria.

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