Tuberculosis Elimination
Are We Willing to Pay the Price?

Zachary Taylor and Richard J. O'Brien

Division of Tuberculosis Elimination, National Center for HIV, STD and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia

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In the December 2000 issue of the Journal (pp. 2079-2086), Dasgupta and colleagues from Montreal evaluate the cost-effectiveness of screening new immigrants for active tuberculosis (TB) and latent TB infection (LTBI) versus screening contacts to infectious tuberculosis patients (1). In most industrialized countries, a substantial proportion of TB cases occur in persons born in other countries (2). In Canada in 1999, 62% of reported TB cases were in foreign-born persons (3), and for the United States the figure was 43% (4). Studies indicate that the majority of these cases arise in persons with LTBI acquired in their birth countries (5). Thus, TB control activities in the United States and Canada increasingly focus on methods to reduce TB in these groups.

Unlike the United States, immigrants to Canada are screened for TB both overseas and after arrival. Dasgupta and colleagues compared the cost-effectiveness of screening immigrant applicants after arrival, surveillance of newly arrived immigrants screened overseas and found to have inactive TB (i.e., radiographic evidence of prior TB), and screening contacts of infectious TB patients. The analysis found that, compared with passive case detection, screening contacts of infectious patients resulted in cost savings for each prevalent case detected and future active case prevented. In contrast, the cost-effectiveness ratios for screening immigrant applicants and surveillance of newly arrived immigrants with inactive TB were $20,328 and $39,409 for each prevalent case detected and $24,225 and $65,126 for each future case prevented, respectively.

However, if only the costs of treating LTBI are considered, screening both immigrant applicants and close contacts results in cost savings for each future case prevented. In addition, improving the efficiency of the applicant screening and surveillance programs resulted in more favorable outcomes and improved cost-effectiveness ratios. The authors concluded that screening programs for immigrants were more expensive than contact investigations and that this finding resulted from operational problems of the two programs.

Major determinants of the cost-effectiveness of screening for TB include the prevalence of active disease or infection, the risk of developing active disease if infected, and the cost of the different components. In this analysis the cost of the programs is the most important factor contributing to the results. However, this is not a consequence of operational inefficiency but rather results from the objectives of the programs and the sequence of tests that are used to achieve those objectives. The objective of the applicant screening program is to identify immigrants with active TB by screening all applicants with a chest radiograph (1). On the other hand, initial screening of close contacts is with the tuberculin skin test (a cost apparently not included in this analysis), with chest radiographs usually indicated only for those with positive skin tests. Nearly half of the cost of the applicant screening program is from the initial chest radiographs that all applicants receive. Although there are improvements in the cost-effectiveness ratios with improvement in program operations, the changes are minor for the applicant screening program and do not result in cost savings under any circumstances for the surveillance program.

Although screening immigrants for TB is costly, it is unlikely that decision makers will make a choice between contact investigations and screening newly arrived immigrants for active TB, because governments have a responsibility to protect their residents from importation of infectious diseases. The report from the Institute of Medicine (IOM), Ending Neglect: The Elimination of Tuberculosis in the United States, challenges this country to increase efforts to address TB among persons born outside the United States by screening all immigrants for both active TB and LTBI and providing treatment of those infected persons at highest risk (6). If this recommendation is to be translated into policy, new resources will be needed to prevent future cases in this population. Cost-effectiveness analysis can help programs decide on the most efficient method of allocating these resources for screening and treating new immigrants for LTBI.

The sensitivity analysis done by the authors shows both the benefits and the limitations of improving program efficiency. Improving the efficiency of immigrant applicant screening by screening only persons from TB endemic countries and by placing 90% of persons with LTBI on treatment resulted in cost-effectiveness ratios of $19,848 per prevalent TB case detected and $16,383 per future TB case prevented compared to $20,328 per prevalent TB case detected and $39,409 per future TB case prevented in the base case (1). Although there was improvement in the cost-effectiveness ratio, the costs to detect a prevalent case and prevent a future case remain high.

If we are going to have a major impact on reducing TB in the foreign-born, we will need to have better diagnostic tests and improved, shorter treatment regimens. In discussing the need for new tools, the IOM report gives highest priority to the development of a more accurate test for LTBI and methods to better identify those at highest risk of active TB (3). Such tools will help to avoid unnecessary costs as well as focus resources for improved outcomes. Although shorter regimens for LTBI treatment have recently become available (7), new drugs to provide for shorter, well-tolerated regimens to improve both acceptance of treatment and adherence are clearly needed if we are to achieve the goal of TB elimination (8).

In the end, what is now needed is the political will to see that the required resources are made available for both strengthening existing control efforts and funding the research required for the development of new tools. As is stated in the IOM report, "The question yet to be answered is whether the renewed opportunity that now presents itself to move toward the elimination of tuberculosis will be seized or whether tuberculosis will be subject to another period of neglect until the next resurgence" (3).

	References

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1. Dasgupta K, Schwartzman K, Marchand R, Tannenbaum TN, Brassard P, Menzies D. Comparison of cost effectiveness of tuberculosis screening of close contacts and foreign-born populations. Am J Respir Crit Care Med 2000; 162: 2079-2086 [Abstract/Free Full Text].

2. Raviglione MC, Snider DE Jr,, Kochi A. Global epidemiology of tuberculosis. Morbidity and mortality of a worldwide epidemic. JAMA 1995; 273: 220-226 [Abstract].

3. Long R, Njoo H, Hershfield E. Tuberculosis: 3. Epidemiology of the disease in Canada. Can Med Assoc J 1999; 160: 1185-1190 [Medline].

4. Centers for Disease Control and Prevention. Reported tuberculosis in the United States, 1999. August, 2000. p. 24.

5. Chin DP, DeRiemer K, Small PM, de Leon AP, Steinhart R, Schecter GF, Daley CL, Moss AR, Paz EA, Jasmer RM, Agasino CB, Hopewell PC. Differences in contributing factors to tuberculosis incidence in U.S.-born and foreign-born persons. Am J Respir Crit Care Med 1998; 158: 1797-1803 [Abstract/Free Full Text].

6. Institute of Medicine. Ending neglect: the elimination of tuberculosis in the United States. Washington DC: National Academy Press; 2000.

7. American Thoracic Society/Centers for Disease Control and Prevention. Targeted tuberculin testing and treatment of latent tuberculosis infection. Am J Respir Crit Care Med 2000;161:S221-S247.

8. Centers for Disease Control and Prevention. Tuberculosis elimination revisited: obstacles, opportunities, and a renewed commitment: Advisory Council for the Elimination of Tuberculosis (ACET). MMWR 1999; 48:1-13.