Bertie Squire of the Liverpool School of Tropical Medicine writes in an article specially commissioned by id21 for World TB Day. There is a dangerous and persistent interplay between tuberculosis (TB) and poverty. TB infection is transmitted more readily in the environmental conditions of poverty: overcrowding, inadequate ventilation and malnutrition. Having TB makes poor people, their relatives and communities poorer still by preventing gainful employment and worsening their social relationships. Yet it is the poor who use proportionally more of their income in accessing treatment for TB than the less poor (Kamolratanakul et al.). This year’s World TB Day theme is therefore welcome in emphasising the needs of TB patients, especially poor TB patients, in balance to the needs of TB services and their targets.

DOTS (directly observed treatment, short-course) is the internationally recognised strategy for TB control. DOTS is a five-point health policy package which emphasises the importance of finding, treating and documenting cure among infectious TB patients (see below). DOTS is widely held to be cost-effective and has received increasing international support over the last decade. One of its major achievements has been the emphasis on achieving high cure rates through consistent and sustained free delivery of approved short-course chemotherapy treatment, and mechanisms to ensure patients take all the prescribed doses. Achieving documented cure in at least 85 per cent of diagnosed patients has been enshrined as the prime target of the DOTS strategy, although debate is still on-going as to the best way to achieve this (Volmink & Garner; Kironde & Meintjies and Macq et al).

Yet whilst free drugs, such as those provided through the DOTS strategy, are vital for TB control, we need to go further. Despite the global emphasis on achieving a cure rate of 85 per cent of diagnosed patients, poor TB sufferers still go untreated. Indeed, there is evidence that over-emphasis on the DOTS cure rate target has led health workers to find informal ways of excluding poorer patients from some DOTS programmes for fear of impairing their chances of demonstrating high cure rates (Singh).

A more systemic problem is that although under the DOTS strategy TB drugs are free, achieving a diagnosis is not, and so the first gateway to treatment is often shut to the poorest (Kamolratanakul et al.). At present, laboratory microscope smear tests on sputum specimens are the only reliable method for TB diagnosis. Making such tests universally free would be an important step forward, but not an easy one (Mundy et al.). Exploring the potential of public-private partnerships, for example, might offer additional ways to opening up further access points for poor patients (Hurtig el al.). In the meantime, the development of a diagnostic tool that reliably detects more TB cases and is less laboratory-dependent than microscope smear tests will be a vital tool in reducing barriers to access. Nonetheless, strengthening laboratory services will remain important for quality-assured TB services and will have important public health benefits beyond TB.

On its own, it is clear that the cure rate target of 85 per cent of diagnosed cases is not enough, as too many cases amongst the poor remain uncounted. Attention is now increasingly on how to achieve the other target of the DOTS Strategy: diagnosing a full 70 per cent of the likely cases in any given population (3rd DOTS Expansion Working Group Meeting).

Reaching this target requires accurate estimation of the number of likely TB cases in a population. Two methods for making such estimates are available, both of which are problematic. Sample-population skin tests identify people who have been exposed to TB by the localised skin reaction they make when TB proteins (tuberculin) are injected under the skin. This method has been complicated however by the widespread population coverage with BCG (Bacille Calmette-Guerin) vaccination, which results in uninfected individuals showing tuberculin skin reactivity. Further, HIV-infected individuals do not necessarily react in the same way, which makes skin-test surveys less reliable in countries with rising HIV prevalence.

A second method involves calculating estimated general infection rates from sample population surveys. This method is hardly ever used in practice because of the investments it requires in planning, time, finances and human resources. The result is that most TB programmes do not know how many TB cases they should be diagnosing and treating each year.

The principles and practice of TB control, including DOTS, have matured in the past 10 years. What are now needed are practical tools that make it possible to estimate expected numbers of TB cases – especially in poorer environments where one can reasonably expect to find more TB cases, and where resources to undertake detailed research are limited. This would allow those who implement TB services to know what case-diagnosis targets they are aiming to achieve, and equally important, what resources need channelling in their direction in order to extend the reach of the DOTS strategy to the global poor.

What's DOTS! ?

DOTS! (directly observed treatment, short-course) is the internationally supported strategy for TB control and consists of:

• Diagnosis in the general health service through direct sputum smear microscopy
• Observation of each treatment dose as the primary means of ensuring adherence to therapy
• Therapeutic monitoring with accurate record-keeping to permit standardised evaluation of case-finding and treatment outcomes
• Short-course drug treatment with tested regimens (for a minimum of six months), regular uninterrupted drug supplies, medications supplied free of charge to patients
• !Government and other stakeholder commitment to TB control

Source(s):
Kamolratanakul P. et al., 2002 'Economic impact of tuberculosis at the household level', International Journal of Tuberculosis and Lung Disease 3(7): 596-602
Mundy C. J. et al., 2002 'Quality assessment of sputum transportation, smear preparation and AFB microscopy in a rural district in Malawi', International Journal of Tuberculosis and Lung Disease 6(1): 47-54
Volmink J. and Garner P., 1997 (Systematic review of randomised controlled trials of strategies to promote adherence to tuberculosis treatment', British Medical Journal 315: 1403-1406. See also updated 2003 Cochrane review, The Cochrane Library, Issue 1, 2003 Full document.

id21 Research Highlight: 24 March 2003

Further Information:
Bertie Squire
TB Knowledge Programme
Liverpool School of Tropical Medicine
Pembroke Place
Liverpool
L3 5QA
UK

Contact the contributor: S.B.Squire@liverpool.ac.uk

Bertie Squire of the Liverpool School of Tropical Medicine writes in an article specially commissioned by id21 for World TB Day.

Other related links:
3rd DOTS Expansion Working Group Meeting, Montreal, October 2002, meeting summary

Godfrey-Faussett P. et al., 2002 'Why do patients with a cough delay seeking care at Lusaka urban health centres? A health systems research approach', International Journal of Tuberculosis and Lung Disease, 6(9): 796-805

Hurtig A. K. et al., 2002 'Linking private and public sectors in tuberculosis treatment in Kathmandu Valley, Nepal', Health Policy and Planning 17(1): 78-89

Kironde S. and Meintjies M., 2002 'Tuberculosis treatment delivery in high burden settings: does patient choice of supervision matter?', International Journal of Tuberculosis and Lung Disease 6(7): 599-608

Macq J. et al., 2003 ‘An exploration of the concept of directly observed treatment (DOT) for tuberculosis patients: from a uniform to a customised approach’, International Journal of Tuberculosis and Lung Disease 7 (1): 1-7

Singh V. et al., 2002 ‘TB control, poverty and vulnerability in Delhi, India’, Tropical Medicine and International Health 7(8): 693-700