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Is it time to reevaluate S’pore’s TB treatment strategy?

We commemorate World Tuberculosis (TB) Day every March 24 to raise public awareness of this ancient infectious disease, which infects over nine million and kills over a million people each year. 

Tuberculosis is a curable airborne disease, with treatment rapidly reducing transmission.

Tuberculosis is a curable airborne disease, with treatment rapidly reducing transmission.

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We commemorate World Tuberculosis (TB) Day every March 24 to raise public awareness of this ancient infectious disease, which infects over nine million and kills over a million people each year. 

In past years, I have written about various interventions and technological adaptations for TB control.

These include expanding the use of smartphone-based video-observed therapy, improving contact tracing to unearth more close contacts of those with TB disease, and initiating treatment for a greater proportion of those with TB infection (previously known as latent tuberculosis infection — where the TB bacilli are in a dormant state and neither cause any symptoms nor spread to others).

At heart, however, TB control is a management — and not medical — challenge for a disease that affects individuals directly but has societal consequences.

Therefore I will focus on individuals with TB disease this time, specifically on what has been a key treatment intervention in Singapore — having healthcare workers observe patients taking their TB drugs in person. 

The majority of individuals with TB disease suffer from TB of the lungs, which is infectious. TB can also cause disease in other organs of the body, but is generally non-infectious in that case, as the TB bacilli spreads mainly through the air.

Globally, TB is treated via a cocktail of drugs that are administered over a period of at least six months.

For history buffs, the clinical trial that defined the effectiveness of a six-month course of treatment was conducted here in the late 1970s by the Singapore Tuberculosis Service in collaboration with the British Medical Research Council.

In persons with drug-resistant TB or who develop severe side effects to the first-line drugs, treatment becomes more complicated and may exceed a year.

The main concern with a long course of treatment involving multiple drugs is that a significant proportion of patients may not complete it, forgetting doses or even stopping completely once they feel better.

Multiple published studies around the world have shown that an average of two or three out of every 10 persons will not complete their TB treatment regimen if left to take the pills by themselves.

Partial treatment may increase the risk of treatment failure, further spread of TB to others, and the creation of drug-resistant TB bacilli.

The reasons for non-adherence to treatment are manifold, and can best be understood by considering TB beyond its technical aspects as an infectious disease, encompassing its broader social and cultural dimensions, including stigma, social inequities, and work-related impediments to treatment.

Non-adherence can broadly be tackled by improving access to and support for treatment, reducing stigma and increasing empathy for patients with TB, as well as improving the relationship between patients and their healthcare providers. 

In 1995, when the World Health Organization launched its Directly Observed Treatment — Short Course (Dots) strategy for TB control, it took into account all of the above but also added the namesake component of direct observation of patients taking TB drugs by a healthcare or community health worker for at least the intensive phase (first two months) of treatment.

Other components of the Dots strategy include sustained government commitment towards TB control, case detection of TB using sputum smear microscopy, uninterrupted supply of TB drugs, and a standardised recording and reporting system that allows for the assessment of the TB control programme’s performance.

Low- and middle-income countries that implemented the entire Dots strategy saw dramatic improvements in TB treatment completion and cure rates. 

The Ministry of Health established the Singapore Tuberculosis Elimination Programme (Step) in 1997 to primarily implement key aspects of the Dots strategy, which it did successfully.

Direct observation of the entire course of TB treatment by a nurse increased from less than 10 per cent of all patients with TB prior to 1997 to 40 per cent in 2001, and more than 70 per cent today.

Data on TB treatment completion rates stratified by type of treatment is not publicly available in Singapore, although a paper published by Step close to two decades ago showed that nine in 10 patients complete the entire course of treatment when directly observed compared to seven in 10 who are on self-administered treatment.

The public health impact of direct observation of treatment on its own is difficult to assess, but TB rates in Singapore fell by just over a third even between 1998 and 2008, before starting to rise again over the next decade.

It is also both costly to implement and imposes significant socioeconomic costs on patients.

A study conducted by SingHealth Polyclinics between 2013 and 2014 showed that almost half of the 356 patients on directly observed treatment that were surveyed perceived that it disrupted work, school and social activities, with 21 per cent believing that their employers were unhappy because it affected their work schedules and duties.

Estimated excess total travelling time for six months of directly observed treatment was 99 hours, with an average cost of S$260 for this period. 

Is direct observation of TB treatment by a healthcare worker necessary today?

Meta-analyses combining the results of large studies have yielded similar results — there is no clear-cut advantage for directly observed TB treatment compared to self-administered therapy with respect to cure of TB disease or treatment completion, particularly if there is more frequent (weekly or fortnightly) contact between patients and their treating physicians.

Direct observation by a healthcare worker in a health facility did not result in better outcomes as well when compared with direct observation by family members or community health workers.

More recent studies have also consistently shown that smartphone-based video-observed therapy is at least as good as directly observed treatment in ensuring treatment completion and cure.

It is timely to reassess our TB control strategy given the lessons and experiences of the Covid-19 pandemic, and decide if we should scale back on efforts to increase the proportion of patients with TB disease on directly observed treatment.

Uncompromising and blunt enforcement of directly observed treatment results in ethical conflicts with patient autonomy and dignity, which we have previously accepted as a price for increased safety of the community from the spread of TB.

It helps to reinforce the wrong moralising judgement that ongoing high TB rates are due to treatment non-adherence of a minority of patients

As more evidence emerges and new technologies are developed, we can better assess and be more precise about which patients require more stringent ways of ensuring TB treatment completion.

Even if the results of Step’s study from two decades ago holds true today, it would mean that at most two or three out of every 10 TB patients might need directly observed treatment.

The resources saved could be ploughed into other interventions with greater potential for bringing down our TB rates, in order that we can do our part in meeting the global TB targets of reducing TB incidence and deaths by 80 per cent and 90 per cent respectively between 2015 and 2030.

 

ABOUT THE AUTHOR: 

Associate Professor Hsu Li Yang is vice-dean of global health and programme leader of infectious diseases at Saw Swee Hock School of Public Health, National University of Singapore.  

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