The Cost-Effectiveness and Public Health implications of Screening for Tuberculosis in Immigrants
Tuberculosis (TB) is a disease that has been a scourge of humanity from at least the time of the ancient Egyptians. The agent of human TB, Mycobacterium tuberculosis, was identified 125 years ago and effective therapy introduced over half a century ago, which many believed would eradicate the disease - at least among the wealthy. However, for multiple reasons (see bullet points below), cases have risen globally since the World Health Organisation declared it a Global Emergency in 1993.
Some reasons accounting for the global increase in TB:
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Almost half of all TB in the USA1 (75% in California2), over half in the UK,3 and two-thirds in Canada1 arises in people born overseas, thus TB screening of immigrants is an important public health priority. Most industrialised countries have screening procedures for TB in place. With the current strain on healthcare and government resources in most countries, it is vital to know whether a TB screening programme is cost-effective.
Several studies have assessed the cost-effectiveness of TB screening programmes for immigrants to industrialised countries, most notably the UK, US and Canada (see table). In the UK, current guidelines from the British Thoracic Society recommend screening all those planning to stay longer than six months coming from high-incidence areas of TB (annual incidence >40 cases per 100,000 of the population).3 This is done at international ports upon arrival, before the individual is referred to the health authority of the district of intended residence.
All immigrants to the USA are required to undergo overseas screening for TB before entry using chest radiograph (and testing for acid fast bacteria, if indicated); those identified as infectious are then barred from entry to the US.2 Individuals with sputum smear-negative active TB and those with inactive TB receive a B-notification, requiring them to report to a local health jurisdiction within 30 days of entry. For applicants to Canada, screening using chest radiograph is conducted for all immigrants wherever the application is made, either overseas or within Canada.4
| Authors | Location | Conclusions |
| Underwood et al. (2003) 5 | UK | Contact tracing more effective at detecting TB than new-entrant screening. |
| Bothamley et al. (2002) 6 | UK | Screening new entrants for TB in primary care found to be feasible, cheap to introduce, and could replace current hospital screening of new arrivals. |
| Dasgupta et al. (2000) 1 | Canada | Contact tracing highly cost-effective, resulting in net savings, compared to immigrant TB screening at entry. |
| Schwartzman & Menzies (2000) 4 | Canada | Chest radiography screening was found to be significantly cheaper and more cost-effective than tuberculin skin testing in screening immigrants for TB from high-incidence countries. |
| Porco et al. (2006) 2 | USA | Current immigration screening programme unlikely to result in a large change in TB cases detected, but domestic follow-up of those with active or latent TB is highly cost-effective and, at times, cost-saving. |
Table: Studies looking at TB screening programmes for immigrants to the UK, USA and Canada.
The cost-effectiveness of methods for controlling TB in immigrants is influenced by the cost of services (transportation, tests, investigations, and hospitalisation), perspective of the analysis (patient, society, or government), and effectiveness of available interventions.7 All costs and cost savings of the interventions described in the studies are estimates, and so the benefits are purely theoretical. Furthermore, the studies were conducted from a governmental perspective, neglecting the direct and indirect costs incurred by immigrants themselves. Existing screening programmes use chest radiographs to detect active TB, which has a low positive predictive value (PPV).7
These studies highlight problems with current screening procedures. For example, screening is only performed once at the time of initial entry to these industrialised countries and approximately 20-30% of all TB cases among foreign-born permanent residents are due to re-exposure during return visits to their country of origin.8 In addition, active TB has a low prevalence among migrants to low-incidence countries at the time of screening, with incidence peaking two to three years after entry.9 Current screening programmes will not detect these individuals. Symptom questionnaires6 may be inaccurate since patients could deny symptoms through fear of being refused entry to their intended country of residence. When taking into consideration the low PPV of chest radiography as a screening tool, and the low prevalence of active TB among immigrants at time of entry to industrialised countries, current TB screening programmes appear to have minimal impact and are not cost-effective.1, 2, 5, 6, 7 The public health impact of TB screening in terms of reduction in secondary transmission remains controversial and difficult to evaluate.4
Some consider current TB screening programmes to be discriminatory, stigmatising, racist and divisive, raising significant ethical issues.5 Also, confidentiality is often breached when compulsory screening is introduced. The clinician has a dual role as a patient advocate and protector of public health. Whilst the aim of a TB screening programme is to protect the wider public, some immigrants may not find such an intervention acceptable, with considerable human rights implications. Perversely, barring entry to those with TB may encourage the avoidance of legal entry routes in the pursuit of illegal routes, or perhaps even encourage the falsification of supporting documentation.
Immigrants often arrive in industrialised countries facing the stress of poverty in a new land, a factor which can activate latent TB. Failed asylum seekers in industrialised countries have it especially difficult financially. Branded by some as ‘health tourists,’ visiting a country with the specific aim of obtaining medical treatment, regulations came into force in the UK in April 2004, for example, requiring these individuals, and others considered overseas visitors, to pay for most hospital treatment.
Evidence for health tourism is lacking and, in fact, a recent study by Médecins du Monde of 349 individuals at Project: London clinics found that people using the service had spent on average three years in the UK before visiting Project: London to see a doctor or to get help in accessing healthcare.10 Fortunately, costs for TB treatment, unlike HIV treatment, are covered by the UK government. However, with regards to cost-effectiveness, it is imperative that asylum seekers have access to early treatment and preventive services, including primary care, since this can avoid the requirement for more costly treatment in the future. Importantly, the denial of free HIV treatment will have a knock on effect for TB rates, since the immunocompromised state of a HIV-infected individual can trigger the activation of latent TB. Schemes to limit access to care are not cost-effective.
The current TB screening programme for immigrants to industrialised countries is not cost-effective and should be reviewed. Alternatives, such as contact tracing within foreign-born communities through local primary care networks, are more cost-effective. The money used for expensive screening programmes could be better placed reducing health inequalities among immigrants - reducing social exclusion, and improving living conditions as well as access to primary care, since poverty and crowded accommodation contribute significantly to the transmission of TB.
Clearly, a multi-disciplinary approach is required, encompassing partnership-working with public health academics, the government, clinicians, charities such as TB Alert, and others. Improvements in both public health infrastructure and adherence to treatment among both doctors and patients through education are vital in increasing the impact and cost-effectiveness of any intervention.
Unfortunately, both the extent of the public health crisis caused by TB and lack of resources to deal with it is unlikely to improve; current resources should be used to yield the highest possible returns. The ideal long-term TB control strategy would focus on investment to reduce global TB incidence - surely a more humanitarian, ethical, and cost-effective way to tackle this significant public health issue.
Matthew A. Kirkman
Fourth year medical student
Newcastle University
matthew.kirkman@gmail.com
1. Dasgupta K, Schwartzman K, Marchand R, Tennenbaum TN, Brassard P, Menzies D. Comparison of Cost-Effectiveness of Tuberculosis Screening of Close Contacts and Foreign-Born Populations. American Journal of Respiratory and Critical Care Medicine 2000; 162: 2079-86.
2. Porco TC, Lewis B, Marseille E, Grinsdale J, Flood JM, Royce SE. Cost-effectiveness of tuberculosis evaluation and treatment of newly-arrived immigrants. BMC Public Health 2006; 6: 157.
3. Joint Tuberculosis Committee of the British Thoracic Society. Control and prevention of tuberculosis in the United Kingdom: Code of Practice 2000. Thorax 2000; 55: 887-901.
4. Schwartzman K, Menzies D. Tuberculosis Screening of Immigrants to Low-Prevalence Countries: A Cost-effectiveness Analysis. American Journal of Respiratory and Critical Care Medicine 2000; 161: 780-9.
5. Underwood BR, White VL, Baker T, Law M, Moore-Gillon JC. Contact tracing and population screening for tuberculosis: who should be assessed? Journal of Public Health Medicine 2003; 25: 59-61.
6. Bothamley GH, Rowan JP, Griffiths CJ, Beeks M, McDonald M, Beasley E, van den Bosch C, Feder G. Screening for tuberculosis: the port of arrival scheme compared with screening in general practice and the homeless. Thorax 2002; 57: 45-9.
7. Dasgupta K, Menzies D. Cost-effectiveness of tuberculosis control strategies among immigrants and refugees. European Respiratory Journal 2005; 25: 1107-16.
8. Ormerod LP, Green RM, Gray S. Are there still effects on Indian Subcontinent ethnic tuberculosis of return visits?: a longitudinal study 1978-97. Journal of Infection 2001; 43: 132-4.
9. The National Collaborating Centre for Chronic Conditions. Tuberculosis: clinical diagnosis and management of tuberculosis, and measures for its prevention and control. London: Royal College of Physicians, 2006.
10. Médecins du Monde. Project: London. Helping vulnerable people to access healthcare: Report 2006. London: Médecins du Monde, 2006.
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