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Page 86 4 Advancing Toward Elimination Once the control of tuberculosis is ensured through the treatment of active cases of tuberculosis, the next step in tuberculosis control is to focus on the prevention of new cases. The relatively long interval between infection with Mycobacterium tuberculosis and the onset of disease creates an opportunity to intervene and prevent disease by treating those with latent infection. Also, as the risk of infection declines, more cases will be the result of reactivation of infection acquired many years earlier. Increasing efforts at prevention can accelerate the decline in the number of cases of tuberculosis, maintain momentum and interest in tuberculosis control programs, and act as preparation for a final push to elimination. This chapter provides an overview of the principles of prevention through treatment of latent infection and proposes strategies for use of this approach with defined populations including foreign-born individuals, especially recent arrivals, from countries with high rates of tuberculosis, inmates of correctional facilities, infected contacts of individuals with infectious tuberculosis, and other high-risk groups that are defined locally. The committee recognizes that many of the strategies described in this chapter will require significant changes and increases in resources at all levels of tuberculosis control but is convinced of the importance of accelerating efforts for the prevention of tuberculosis. RECOMMENDATIONS Recommendation 4.1 To limit the spread of tuberculosis from infec
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Page 87 tious patients to their contacts, the committee recommends that more effective methodologies for the identification of persons with recently acquired tuberculosis infection, especially persons exposed to patients with new cases of tuberculosis, be developed and efforts be increased to evaluate appropriately and treat latent infection in all persons who meet the criteria for treatment for such infections. Recommendation 4.2 To prevent the development of tuberculosis among individuals with latent tuberculosis infection, the committee recommends that Tuberculin skin testing be required as part of the medical evaluation for immigrant visa applicants from countries with high rates of tuberculosis, a Class B4 immigration waiver designation be created for persons with normal chest radiographs and positive tuberculin skin tests, and all tuberculin-positive Class B immigrants be required to undergo an evaluation for tuberculosis and, when indicated, complete an approved course of treatment for latent infection before receiving a permanent residency card (“green card”). Implementation should be in a stepwise fashion and pilot programs should evaluate and assess costs. Tuberculin testing be required of all inmates of correctional facilities and completion of an approved course of treatment, when indicated, be required, with referral to the appropriate public health agency for all inmates released before completion of treatment. Programs of targeted tuberculin skin testing and treatment of latent infection be increased for high-incidence groups, such as HIV-infected individuals, undocumented immigrants, homeless individuals, and intravenous drug abusers, as determined by local epidemiological circumstances. BACKGROUND AND INTRODUCTION The recent success of tuberculosis control efforts indicates that, given adequate resources, the traditional control program that focuses on the treatment of active tuberculosis is once again functioning effectively and that a steady decline in cases should be expected. However, to make significant progress toward the elimination of tuberculosis in the United States, efforts to prevent cases from occurring must be amplified. Without an effective vaccine for the prevention of pulmonary tuberculosis, the most effective means of preventing new cases is to take advantage of the relatively long period between infection and the development of active
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Page 88 disease by treating individuals with latent infection to reduce the risk of disease. The Advisory Council for the Elimination of Tuberculosis (ACET) included expanded targeted testing and treatment of latent infection among the highest-priority activities for tuberculosis control programs (CDC, 1999). Recently published guidelines from the Centers for Disease Control and Prevention (CDC) and the American Thoracic Society will provide a framework for increased attention to targeted screening and will recommend new regimens for the treatment of tuberculosis infection (American Thoracic Society and CDC, 2000). As recommended by the guidelines and by ACET, local epidemiological conditions will guide the testing effort, but increased national attention will be needed in three areas. First, as noted in Chapter 2 , tuberculosis among foreign-born individuals accounts for an increasing proportion of U.S. tuberculosis cases, and slightly more than half of these cases occur within the first 5 years of the arrival of foreign-born individuals in the United States. Targeted tuberculin skin testing of newly arrived immigrants before arrival in the United States with adequate treatment for those with latent infection once they arrive could prevent a significant number of cases. Second, an outbreak of tuberculosis associated with a prison led to the recognition of the resurgence of tuberculosis in the United States, and screening for infection and treatment of latent infection should be mandatory in these settings. Finally, by challenging traditional concepts about contact investigations and expanding the definition of close contacts to include social contacts and others previously thought to be at lower risk of infection, many more recently infected individuals who are at an increased risk of developing tuberculosis will be identified. This chapter provides a brief background on the rationale for the treatment of latent infection and addresses these priority areas for the prevention of tuberculosis. TREATMENT OF LATENT TUBERCULOSIS INFECTION Shortly after the discovery of isoniazid in 1952, the potential of this highly bactericidal drug to prevent tuberculosis was explored. A series of trials summarized in a review by Ferebee (1970) showed that the effectiveness of isoniazid for the prevention of tuberculosis ranged from 92 percent in an outbreak among Dutch sailors, in which adherence to the regimen was strictly enforced (Veening, 1968), to 26 percent in a Tunisian community-based study in which the rate of adherence to the isoniazid regimen was estimated to be only 25 percent or less. A study of 3-, 6-, and 12-month regimens showed that a 12-month regimen was the superior regimen (International Union Against Tuberculosis, 1982) and Comstock (1999) recently presented an analysis that showed that a regimen of at least 9 months likely gives maximum protection.
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Page 89 Isoniazid can cause hypersensitivity reactions, paresthesia, and other adverse effects, but concerns about isoniazid hepatotoxicity have limited the use of isoniazid in the past for the treatment of latent infection. However, this controversy concerns the provision of isoniazid to individuals at relatively low risk of tuberculosis. In contrast, the use of isoniazid has never been challenged for individuals at high risk of tuberculosis, including recent tuberculin skin test converters, contacts of infectious patients, immigrants from countries with high rates of tuberculosis, and individuals with certain medical conditions, especially human immunodeficiency virus (HIV) infection. A recent 7-year study of patients receiving isoniazid for treatment of latent infection showed a rate of clinical hepatitis of only 0.1 percent (11 cases among 11,141 patients), with no deaths and only one hospitalization in a program with patient monitoring, the administration of only limited amounts of medication at each visit, and good education on the symptoms of adverse effects (Nolan et al., 1999). In addition to isoniazid, rifampin-based regimens have recently been recommended as treatment for latent infection with M. tuberculosis (American Thoracic Society, 2000). The current recommended regimens for treatment of latent infection include isoniazid for 9 months (with an option for 6 months), rifampin and pyrazinamide for 2 months, and rifampin alone for 4 months (ATS/CDC statement). Although the rifampin-pyrazinamide regimen has the advantage of being much shorter, the experience with this regimen is relatively limited, and one pilot study that evaluated this regimen showed that it has a very high rate of toxicity. In particular, this regimen has not been evaluated with immigrant populations, and programs that use the regimen are encouraged to maintain surveillance for adverse reactions to this regimen. CURRENT SCREENING FOR IMMIGRANTS TO THE UNITED STATES As noted in Chapter 1 , increasingly large proportion of tuberculosis cases in the United States occur among foreign-born individuals: 7,591 (41.3 percent) cases in 1998. If the number of U.S.-born individuals with tuberculosis continues to decrease at a rate of 9 percent, as it did between 1992 and 1998, and the number of foreign-born individuals with tuberculosis remains the same, the majority of tuberculosis cases will occur among foreign-born individuals from 2002 onward. The CDC Working Group on Tuberculosis Among the Foreign-Born thus concluded that the elimination of tuberculosis in the United States will increasingly depend on the elimination of tuberculosis among foreign-born individuals. Foreign-born individuals comprise those who arrive in the United States through a number of mechanisms. The majority who come to the
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Page 90 United States legally are in the United States temporarily. These arrivals include tourists, students and their families, and workers and their families. Immigrants include those who intend to reside permanently in the United States, some who have newly arrived from their country of origin, and others who adjust their status to permanent residency while they are already in the United States. Tuberculosis is one condition for which immigrants are screened before they enter the United States. This screening currently consists of a chest radiograph for all immigrants 15 years of age and older and the examination of three sputum samples for acid-fast bacilli (AFB) for all individuals with chest radiograph findings consistent with tuberculosis. Immigrants younger than 15 years of age who are suspected of having tuberculosis or of having contact with an individual with a known case of tuberculosis are given a tuberculin skin test, and those with any indication of tuberculosis are given a chest radiograph. Individuals with any sputum tests positive for AFB are classified as infectious and as having a Class A medical condition. This means that either they must complete an approved course of tuberculosis treatment before entering the United States or that they must start therapy and have three consecutive negative sputum tests before coming to the United States. Individuals who do not complete therapy must have a relative arrange for treatment at the intended destination in the United States, with the concurrence of the local or state tuberculosis control program. They are to be given 30 days of medication when they depart for the United States. Individuals who have abnormal chest radiograph and sputum examinations but who are negative for AFB are classified as having a Class B medical condition: Class B1 if the radiograph indicates active disease but the individual is not infectious due to negative sputum smears or if the individual has extrapulmonary tuberculosis (such individuals are to be started on therapy and given 30 days of medication before coming to the United States); Class B2 if the radiograph indicates tuberculosis that is not clinically active; and Class B3 if the radiograph indicates old or healed tuberculosis. Individuals with Class B1 or B2 tuberculosis are told to report to the public health department at their final destination. Any Class A or B medical classification is recorded on immigration documents (DQ [Division of Quarantine] form 75.17). If the immigrant enters one of the eight ports (Honolulu, Seattle, San Francisco, Los Angeles, Chicago, Miami, Atlanta, and New York) where U.S. Public Health Service Division of Quarantine staff are assigned, the quarantine officer gives the immigrant a form that reminds the individual of the requirement to report to the local public health department upon arrival at the
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Page 91 final destination. The quarantine officer sends DQ form 75.17 to the CDC Division of Quarantine, which then forwards the forms to state and local health departments. If the immigrant arrives in a port without a quarantine officer, the immigration officer is to collect the form (DQ form 75.17), notify the immigrant of the requirement to report to the local public health department upon arrival at the final destination, and then send DQ form 75.17 to the nearest port with a quarantine officer. There has been no evaluation of the rate of referral of immigration forms from ports without a quarantine officer, but it is believed that many of the forms are not collected and that when they are collected they are often held for long periods of time and sent to a port with a quarantine office in batches. When the immigration forms are collected and sent to health departments, the follow-up rate of screening of immigrants for tuberculosis can be quite high. It has been estimated to exceed 82 percent in most areas of the United States (Binkin et al., 1996), and one tuberculosis control program has documented a follow-up program that achieved a 97.5 percent follow-up rate (Catlos et al., 1998). However, it costs the program $13–$14 immigrant to follow-up each new arrival and to encourage the individual to report for examination, and the program accounts only for those immigrants about whom the health department was notified by the Division of Quarantine. THE NEED FOR EXPANDED SCREENING More than a quarter (29.6 percent) of all cases of tuberculosis among foreign-born individuals occur during the first year after their arrival in the United States, and more than half (55.5 percent) occur during their first 5 years in the United States. The risk for developing tuberculosis declines the longer an immigrant from a country with a high risk of infection is in the United States, because they are no longer at a high risk of infection or reinfection. While the risk of developing tuberculosis for a recently arrived immigrant from a country with a high risk of infection is lower than that of a newly infected person, the risk for the typical immigrant from a high-risk country is many times that of the typical U.S. resident. The current screening procedure for immigrants does not and cannot detect or prevent many of the cases of tuberculosis that occur among foreign-born individuals in the United States. Recent immigrants from countries with high rates of tuberculosis have been identified as prime candidates for screening and treatment of latent infection (American Thoracic Society, 2000), but public health efforts to confront the problem have been inadequate (Binkin et al., 1996). The Working Group on Tuberculosis Among the Foreign-Born concluded,
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Page 92 Efforts to provide screening and preventive therapy for the foreign-born are limited. Averting future cases of TB [tuberculosis] requires linking screening programs to prevention services. However, few resources are available to health departments for prevention efforts to foreign-born persons. Also, persons who do not consider themselves ill and who are from countries where TB is reported as a stigma might be reluctant to begin or complete therapy (Centers for Disease Control and Prevention, 1998:7) In the current system, the burden is on the health departments to encourage individuals to be screened for tuberculosis infection after they arrive in the United States. Given the significance of tuberculosis among foreign-born individuals and given the contribution that addressing the incidence of tuberculosis among foreign-born individuals would make to the goal of tuberculosis elimination, the committee believes that the federal government should fund a coordinated national effort to screen foreign-born individuals for tuberculosis. Reliance on the efforts and resources of local health departments unfairly burdens those communities within which a disproportionate number of foreign-born individuals reside, fails to reflect the national interest in radically reducing the rate of tuberculosis among immigrants and refugees, and virtually ensures that the level of commitment will be inadequate for the task. The strategies that must be developed are linked to the impediments to identifying those with latent tuberculosis infection and ensuring their completion of treatment for latent infection, the sheer size of the populations to be screened, the difficulties in gaining access to those who should be screened, and the cultural and linguistic barriers that make voluntary approaches to screening and treatment of limited utility. A significant departure from current methods of screening and treatment of latent tuberculosis infection among foreign-born individuals is dictated by the clear public health benefits that could be attained. Strategies to Ensure Case Identification and Treatment Completion A first step would be to expand the current screening of those applying to immigrate and the screening of refugees. Tuberculin skin testing for latent infection should be added to the current panel of tests used to screen for active tuberculosis (chest radiographs and sputum analysis), and a Class B4 (or other designation) should be created for individuals with a normal chest radiograph but a positive tuberculin skin test. Such testing, like other medical examinations, would occur before the immigrant or refugee came to the United States. Tuberculin skin testing already occurs in the United States for those seeking to adjust their status
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Page 93 after coming to the United States on temporary visas. Given the small number of tuberculosis infections detected by tuberculin skin test screening among low-risk populations and the recent recommendations of the American Thoracic Society and the CDC that screening for latent infection be targeted to those at risk, there is little justification for screening all applicants for immigration. Targeting of screening to those who come from countries with the greatest tuberculosis burdens (prevalence of infection estimated to be equal to or greater than the global median of 36 percent) would detect the greatest number of infections and would require the testing of approximately 200,000 immigrants per year. Individuals born in countries with the greatest burdens of tuberculosis account for 55 percent of the cases of tuberculosis among the foreign-born individuals each year. In particular, even though Mexico is estimated to have only a 17 percent prevalence of tuberculosis infection, Mexican-born individuals account for nearly one-quarter of the foreign-born individuals with tuberculosis each year and just under 10 percent of the total number of individuals with tuberculosis in the United States. Requiring immigrants from Mexico to be skin tested before immigration would add about 53,000 immigrants to the testing program each year, increasing the total number of immigrants to be skin tested each year to about 250,000. Among each annual cohort of immigrants from countries with the greatest tuberculosis burdens, approximately 2,100 cases of tuberculosis can be expected to occur over the course of a cohort's first 5 years in the United States. Assuming a steady influx of immigrants, this rate of tuberculosis among each cohort translates into 2,100 cases per year among the population of immigrants who arrived in the past 5 years. As noted in Appendix E , data on the rate of tuberculosis among immigrants have a number of limitations, and estimates obtained by using more recent population and immigration estimates from the 2000 census would be valuable. Identifying and Treating Latent Infection The methodology for estimating the number of cases that could be expected to occur among foreign-born individuals, the number of cases that could be prevented by treatment of latent infection, and the costs of a program for the treatment of individuals with latent infection are contained in Appendix E . Assuming an overall rate of effectiveness of treatment for latent infection of 75 percent (allowing for nonadherence), at least 1,300 cases of tuberculosis could be prevented per year during the first 5 years that the immigrants are in the United States. (The number of cases prevented in later years, when the immigrants are at a lower risk of developing tuberculosis, was not estimated.) Overall program costs would be about $23 million per year, and the cost per case of tuberculosis pre
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Page 94 vented would be about $14,559, which is less than the cost of treating a patient with tuberculosis and monitoring the contacts of that patient, which is $16,391. If the results of the tuberculin skin testing before immigration were accepted and the test was not repeated, the program costs would drop to about $12,305 per case of tuberculosis prevented. Additional savings will be realized if all individuals with a Class B tuberculosis designation were required to report for tuberculosis screening in the United States. As noted above, tuberculosis control programs are very successful in getting immigrants with a Class B tuberculosis designation to report for examination. However, although such screening is cost-effective, it is cosily, and screening of foreign-born individuals with Class B tuberculosis would account for about 12 percent of the tuberculin skin testing costs described above. Shifting the burden to report for screening to the arriving immigrant would reduce the need for intensive follow-up, and the cost per case of tuberculosis prevented could be reduced to $12,920 if all immigrants reported without follow-up. One method of requiring examination for tuberculosis and tuberculosis infection would be to withhold the “green card” for all immigrants with a Class A or Class B tuberculosis designation and to issue this permanent residency document only when these individuals have completed screening by the health department and treatment (if indicated). This approach may shift costs from the public health programs to the Immigration and Naturalization Service (INS), but the immigrants would have a strong incentive to comply. However, the service may not be as costly if modern information technology is applied. At a minimum, the failure of an immigrant with a Class B tuberculosis designation to report to the health department for screening could be made grounds for deportation, as is already the case for immigrants with a Class A designation and a waiver to enter the United States. Issues and Concerns The committee carefully considered the issues surrounding tuberculin skin testing and treatment of latent infection for newly arrived immigrants. An extra public session was added to the committee's schedule to allow a roundtable discussion of the ethical, legal, and practical issues of implementing these programs. After these discussions the committee concluded that the difficulties in implementing the program were largely structural but that these could be overcome with a sufficient commitment of resources. Although these costs will be significant, many of the benefits will accrue to the general programs of targeted tuberculin skin testing and the treatment of individuals with latent infection. Significant additional funding will be required for (a) CDC to provide training and moni
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Page 95 tor the quality of the tuberculin testing programs, (b) CDC and INS to ensure that information on the immigrants is collected accurately and is promptly communicated to the relevant health departments in the United States, and (c) the state and local health departments that will have to provide the final medical examination and that will be responsible for completion of therapy, when treatment is indicated, including start-up costs for training and infrastructure. However, improvements are needed in the current system of testing for and treatment of latent infections, and this new program could pave the way for a broad array of needed changes. Because of the magnitude of the changes required by this recommendation, the committee suggests that this be implemented in a stepwise approach and that pilot programs be developed to evaluate strategies and assess their costs. The adoption of a mandatory tuberculin skin test screening program may trouble those concerned with the human rights of immigrants and refugees, foreign workers, and students. In a national climate characterized by occasional hostility to immigrants and assumptions about the burdens posed by foreign-born individuals, it is not difficult to understand such concerns. Nevertheless, the committee can see no fundamental reason why the logic of current tuberculosis screening should not be extended to those with latent infection. Although the threat to the public health from latent infection is not as immediate as the threat that stems from active disease, the overall epidemiological burden is significant. It is that potential burden that justifies such screening. Treatment of Latent Infections No program of mandatory screening for latent infection could be justified unless it were linked to a program of treatment of latent infection. Recent analyses have made clear that with isoniazid monotherapy, the recommended course of therapy should be isoniazid therapy daily or twice weekly for 9 months (American Thoracic Society, 2000). A two-drug regimen of rifampin and pyrazinamide daily for as little as 2 months has also been shown to be effective at reducing the risk of disease by the same amount as the 9-month isoniazid regimen, but as noted earlier, toxicity may be an issue for the rifampin-pyrazinamide regimen. For both the long-term monotherapy and the short-course, 2-month regimens, strict adherence to the treatment regimen is crucial. A positive tuberculin skin test should not impede the entrance of immigrants, refugees, workers and students to the United States. Should the treatment of latent infection, however, be voluntary or mandatory? Reluctance to mandate treatment of latent infection is rooted in concerns about the risks associated with such treatment as well as in constitutional
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Page 96 and ethical principles. As noted above, early experience with isoniazid treatment raised questions about its hepatotoxicity. However, it has always been clear that the benefits of isoniazid treatment outweigh the risks of toxicity for those at high risk of tuberculosis. Recent experience has made clear that careful clinical monitoring and the exclusion of those at very high risk of hepatotoxicity can radically reduce the risks associated with treatment of latent infection. Nevertheless, the risks are not absent. These lingering risks, however, along with concerns for individual rights, no longer justify the basic claim for relying solely on voluntary treatment programs. Payment for Treatment and Community Support Although the committee acknowledges the importance of protecting and respecting the rights of immigrants and refugees, it believes that the vast public health benefit that would follow from universal treatment of those with latent infection, as recommended by the American Thoracic Society, justifies the imposition of therapy. The federal government, in recognition of the fact that such therapy is primarily designed to achieve a public health goal of national importance, should pay for the treatment of immigrants and refugees. Although the payment for treatment should be from public funds, the provision of treatment should be undertaken in a range of settings. Given the cultural and linguistic barriers that confront individuals who have newly arrived in the United States, much might well be attained by engaging the cooperation of community-based organizations that provide services to distinct ethnic immigrant communities. Certainly such organizations will have much to offer local tuberculosis control programs that may be called upon to provide treatment of newly arrived immigrants for latent infections. Nonpermanent Residents Screening of immigrants for latent tuberculosis infection and treatment (if necessary) will not affect students, workers, and their families who come to the United States for long-term stays but do not seek permanent residence. In 1996, 280,000 new arrivals from countries with a high incidence of tuberculosis were students, workers, and their families, and an additional 2,000 cases of tuberculosis per year may occur among these individuals during their first 5 years in the United States. The estimated number of these cases is smaller than that for permanent visa applicants because of differences in the incidence of tuberculosis in their countries of origin. This also is likely to be an overestimate of the number of cases as many of these people would not be in the United States for the full 5
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Page 111 tion problems are common throughout the investigation process (Barnes et al., 1991), and as no standardized methodology for data upkeep, analysis, or evaluation exists or is required, programs approach these tasks differently. Additionally, no national, consensus guidelines for tuberculosis outbreak investigations exist such as response plans or procedures. Tuberculosis programs were required to have an “outbreak response plan” as part of their Year 2000 Cooperative Agreement grant applications for funding from the CDC, but no guidance was given on a standardized approach. The newly established CDC Contact Working Group could serve as a vehicle to facilitate the development of much needed standardized recommendations and implementation strategies, such as definitions, common elements, and formats for data collection (including factors that place an individual at high risk for tuberculosis and at high risk of a lack of adherence to treatment), methods for assessment of all contacts (tuberculosis skin test positive or negative) for factors that place them at high risk for tuberculosis and prioritization for follow-up on the basis of these factors, methods for ensuring counseling for the prevention of HIV infection and testing for all individuals at risk for HIV infection, methods for determination of the date of last exposure, and evaluation standards. Collaboration with the National Tuberculosis Controllers Association could assist with this process. In addition, current state or big city contact investigation guidelines (where they exist) and other related materials (algorithms, fact sheets, etc.) can be reviewed as potential models or examples. As part of its global efforts, CDC could work with the International Union Against Tuberculosis and Lung Diseases Nursing Section's International Working Group on Contact Investigations. This group has developed a list of international referrals to be used to monitor contacts who leave the state or country. Lack of Knowledge About Need for and Importance of Contact Investigations Contact investigation education has three components: provider education (including public health), patient and contact education, and the patient-provider relationship. Provider Education A major difficulty for providers is priority setting. Those who lack training and experience often do not understand the need for a systematic approach to the investigation. Providers may also lack knowledge as to who is at risk of progression to disease, and resources may be spent on
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Page 112 delivering services to individuals who are not at demonstrated risk. The lack of a standardized approach to tuberculin skin testing and reading of the results may also result in misinterpretations that may confound the process. Finally, there are failures to recognize an outbreak and to expand an investigation when needed (Barnes et al., 1991). Patient and Contact Education A delay in diagnosis may result when a patient with tuberculosis fails to seek treatment. Asch and colleagues (1998) have reported that 30 percent of symptomatic patients with tuberculosis did not obtain medical attention for more than 30 days after the onset of symptoms. This delay adds to the potential for transmission to contacts. The reasons for this delay may include patient or contact mistrust of the government or health care system or related immigration issues. Cultural beliefs that cause fear of stigmatization because of tuberculosis, tuberculosis and HIV coinfection, or other factors may also interfere with the contact investigation process. Patients may be reluctant to divulge contact information if they are worried about the perceptions of others. The lifestyles of many tuberculosis patients result in competing priorities. Drug use or the need for food and shelter for homeless people may take priority over medical care. Although some patients readily provide the names of their contacts, misunderstandings about how tuberculosis is transmitted may lead to misunderstandings of what a true contact is and the patient may inadvertently miss some critical information (Shrestha-Kuwahara et al., 1999). Patients are also often reluctant to identify risk factors for HIV infection. Finally, among foreign-born individuals, there are misconceptions about the receipt and presumed protectiveness of the BCG vaccine. Many of these factors result in the failure of contacts to respond to the screening efforts (Brassard and Lamarre, 1999; Hussain et al., 1992). For example, in a church choir outbreak (Mangura et al., 1998), few persons (less than one-third) who were exposed participated in the initial skin testing and one-third of those who did participate did not return for readings of the skin test results. Similar findings have been found in other settings, such as a pediatric outpatient clinic, where, despite extensive resource dedication, only 43 percent of exposed children completed screening (Moore et al., 1998). Patient-Provider Relationship The patient-provider relationship is often complicated by different attitudinal beliefs and social or cultural differences. Either the interviewer, the interviewee, or both may be uncomfortable with the HIV risk assess
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Page 113 ment questions. Also, as mentioned previously, the patient's perceptions of contact may be different from the provider's epidemiological perceptions of contact with tuberculosis (Booysen et al., 1999). To overcome all of these obstacles, providers need skills in patient assessment, interviewing, counseling, communication, skin testing, and reading and evaluation. Models exist for some of these areas, such as training courses in contact investigation and interviewing skills offered through CDC-funded Model Tuberculosis Centers. The New Jersey Model Tuberculosis Center, for example, offers improved contact investigation interviewing techniques through innovative skills-based training. If offered on a regional basis (with adequate supportive funding), this type of training would allow more participation and interaction by providers with patients. These courses should also promote the development of skills in basic environmental assessment techniques for use in field investigations. CDC, in conjunction with the Model Tuberculosis Centers, recently offered via the Internet a self-study module on contact investigation that was reportedly quite successful. The CDC also plans to release this material on videotape and as an interactive computer-based course. Patient and provider educational materials are needed to facilitate the contact investigation process. Educational materials for patients need to be culturally and linguistically appropriate, as well as at the correct level of literacy for the targeted population, and they need to be evaluated to assess their effectiveness. Committee members were not aware of efforts by either CDC or the Model Tuberculosis Centers to develop these materials and encourage their development, along with the other patient educational materials discussed in Chapter 3 . Before the development of the educational materials, appropriate theories and models of behavioral change need to be evaluated and used as appropriate to deliver effective, targeted messages, materials, and programs for health care providers and patients. The patient-provider relationship would be enhanced through cultural awareness training for providers. Some tuberculosis programs have already established such training programs, and these programs or models from other disease control programs should be available to all providers. The patient-provider relationship will also be enhanced by training in skills in counseling for the prevention of HIV infection and testing for HIV infection, which should be widely available to all providers. Data The lack of knowledge as to what types of data are needed can significantly affect the quality and performance of the contact investigation. This problem was noted in a study conducted in several state and big city
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Page 114 tuberculosis control programs (Marks et al., 1999). Their results indicate that there were great variations as to who was collecting data from the sites surveyed, as well as what information was being obtained. The study noted that less information was recorded for individuals who were tuberculin skin test negative or who did not begin treatment for latent infection, no contacts were noted for many patients with tuberculosis, no notation that identified persons at high risk for disease (especially HIV) was found, and risk factors for nonadherence to treatment were rarely recorded. In a presentation to the committee it was noted that 2 of 11 programs surveyed did not record the date of last exposure to establish time frames for investigation, and no record of follow-up skin tests was noted for 43 percent those who were initially negative (Onorato, 1999). The lack of general prevalence data on which to base a decision to expand (or not expand) an investigation is also problematic. Although the current expansion of the National Health and Nutritional Examination Survey (NHANES) to include tuberculosis will collect some general prevalence data, given the type of sampling used for that survey, it is questionable whether the results from that survey can be extrapolated for use in contact investigations. Regarding data accessibility, studies have shown that the inability to obtain information can profoundly affect the results of the investigation (Hussain et al., 1992; Nivin et al., 1998). For example, in a tuberculosis outbreak in a hospital nursery (Nivin et al., 1998) contact investigation difficulties included the fact that inadequate data on tuberculin skin testing of hospital employees were available and many records could not be located at all. The CDC Working Group on Contact Investigations or a similar group should develop guidelines for data collection: what types of data are needed, where data should be maintained, how many data should be collected, and so on. Guidelines should outline and specify the types of data required for all aspects of the contact investigation process, followup, analysis, and evaluation. There is also a need for community-specific tuberculosis prevalence data, if that is to be the measure used for comparison in the expansion of investigations. If this is not feasible, then alternative means of decision making need to be developed and disseminated. Health departments should work with health care providers to ensure that contact testing data are accessible when they are needed. Laws that allow public health agency access to data for investigations of infectious diseases should be enforced, and provider collaboration with public health agencies should be enhanced.
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Page 115 Framework The current contact investigation process does not appear to adequately incorporate host susceptibility into the priority-setting process. For example, contacts who are infected with HIV may belong in the first group of contacts evaluated, regardless of the extent of contact. Another factor associated with the determination of host susceptibility relates to the adequacy of HIV risk assessment techniques used during the contact investigation process (particularly for those who are skin test negative) (Barnes et al., 1991; Barnes et al., 1996). If these techniques are not adequate, persons at the highest risk of disease may be missed. Recent data also suggest that the concentric circle method (i.e., examining groups at lower risk of exposure only if the higher risk group had a high rate of infection) may not completely address contact investigation needs (Bock et al., 1998; Cegielski et al., 1997; Fitzpatrick et al., 1999; Mangura et al., 1998; Rothenberg, 1996). Some of these investigators have suggested that this traditional approach be modified or changed to reflect the influence of social networking. Two recent reports highlight this need. In an investigation of a church choir, all cases of tuberculosis were reported separately by each township in quite diverse communities (Mangura et al., 1998). Traditional contact investigation methods had identified no workplace or family contacts. In the investigation of participants in a floating card game described earlier in this chapter, the failure to identify the existence of numerous social networks propagated the outbreak (Bock et al., 1998). These examples demonstrate the importance of congregate activities outside of work and the importance of assumed socially defined high-risk groups. The role of DNA fingerprinting in contact investigations needs to be further defined. Three recent reports suggest the importance of molecular epidemiology in understanding the application of the current contact investigation framework. In the first of these, the conventional means of contact investigation failed to identify epidemiological links, in which typing by restriction fragment length polymorphism (RFLP) analysis led to the detection of a community outbreak among HIV-infected persons (Tabet et al., 1994). The common place of transmission was a local bar. A second example was an investigation in Los Angeles in which RFLP analysis showed that the locations at which the homeless population congregate were important sites of tuberculosis transmission for both homeless and nonhomeless people (Barnes et al., 1997). Finally, a study in Baltimore by Bishai and colleagues (1998) suggests that measures to reduce tuberculosis transmission should be location specific instead of based on the concentric circle method. RFLP analysis in the context of contact investigations also raises the issue of reopening such investigations on the
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Page 116 basis of new results by RFLP analysis. The costs and benefits must still be assessed to evaluate this strategy. If research demonstrates that new frameworks for contact investigations such as social networking or location-based screening are effective, health department staff and other providers will require training in their applicability and use. Education on tuberculosis and contact tracing strategies will need to be adapted to the characteristics of distinct population groups. Expansion of screening programs might be applicable for groups at increased risk of transmission, particularly if it seems that traditional contact investigations are not feasible. Safety and Confidentiality Safety and confidentiality issues reflect the changing world of tuberculosis and the associated program implications for investigators. Safety for the investigator is an issue, given the high-crime-rate areas where contact investigations are frequently conducted. Decisions need to be made about security, and plans to ensure safety should be developed as needed (Bock et al., 1998). In addition, confidentiality can be difficult to maintain in some settings, particularly during workplace- and institution-based outbreaks. Research The lack of a scientific basis for some aspects of the contact investigation process affects the potential effectiveness and efficiency of the investigation and restricts the investigator's ability to stop further transmission of disease. This is particularly true in the determination of transmission factors. As noted earlier, it is still not possible to define precisely the limits of the contact investigation. Although mathematical models for analysis of potential transmission of tuberculosis are available, the factors that affect both the transmission and the acquisition of disease are variable and difficult to calculate (Nardell et al., 1991). For example, there are continued difficulties in defining the extent of “infectiousness.” Although the transmission risk assessment provides some direction, it lacks scientific validation, and some of the variables are open to question (e.g., the relationship between transmission and smear status [as noted earlier], patients with “normal” chest X rays, and the clinical presentation in children) (Barnes, 1998; Behr et al., 1999; Corless et al., 1999; Iseman, 1997; Kenyon et al., 1997; Menzies, 1997a; Pena et al., 1999). Differences in the virulence of the infecting organism also affect transmission. The ability to define such virulence would help the investigator to better prioritize contact efforts by being able to focus on those who are
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Page 117 defined as potential “superspreaders” (Valway et al., 1998; van Soolingen et al., 1996; Zhang et al., 1992). The reverse is also true for children, who are not usually considered infectious. A better understanding of transmission factors as they relate to children would assist the investigator in decision making in such difficult settings as schools or day-care centers. A better definition of the protection afforded by the BCG vaccine and its relevance to exposure would also help define those at risk of transmission (Menzies, 1996). There are also continued difficulties in defining environmental factors such as direction of airflow, volume of ventilation, the presence of ultraviolet light, crowding, and volume of air space. Finally, the recent recommendations of ACET suggest that operational research is needed to (a) ensure prompt and complete identification of contacts, (b) increase the numbers of appropriate contacts who are identified, (c) increase the proportion of infected contacts who are placed on treatment for latent infection, and (d) and increase the proportion who complete therapy (CDC, 1999). Conclusion If tuberculosis elimination efforts are to be successful, prevention activities must be targeted to the groups at highest risk for progression from tuberculosis infection to disease. Contacts of patients with infectious cases of tuberculosis are such a high-risk group, and the tracing of contacts should be priorities for tuberculosis control programs. Although the focus of contact tracing is prevention, other potential benefits of the investigation may include the identification of additional cases of tuberculosis and the opportunity for education about tuberculosis disease, the risk of transmission, the tuberculosis-HIV connection, and so on. As every case of tuberculosis began as a contact, the ability to rapidly identify tuberculosis cases and to effectively conduct the subsequent contact tracing is one of the cornerstones of tuberculosis control efforts by public health agencies. Without this capacity, transmission of tuberculosis will persist, the decline in the numbers of cases of tuberculosis will stop, and tuberculosis elimination will be impossible to achieve. REFERENCES Allos BM , Gensheimer KF , Bloch AB , Parrotte D , Horan JM , Lewis V , and Schaffner W. 1996 . Management of an outbreak of tuberculosis in a small community . Ann Intern Med 125 : 114–117 . American Thoracic Society/American Lung Association . 1992 . Control of tuberculosis in the United States . Am Rev Respir Dis 146 : 1623–1633 . American Thoracic Society and Centers for Disease Control and Prevention . 2000 . Targeted tuberculosis testing and treatment of latent infection . Am J Respir Crit Care Med 161 : 5221–5247 .
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Representative terms from entire chapter: