10 misconceptions about drug-resistant TB

10 misconceptions about drug-resistant TB

1. Drug-resistant tuberculosis (DR-TB) only exists in specific countries or regions, mostly in the former Soviet Union

Most evidence on DR-TB has been limited to developed countries. In 1992, the Third World Congress on Tuberculosis said there was little recent information on the global magnitude of multidrug-resistant tuberculosis (MDR-TB), defined as resistance to at least two drugs – Isoniazid and Rifampicin. A World Health Organization (WHO) review published in 2003 states: ‘… the data available suggest that globally MDR-TB is not a problem of the same magnitude as that of drug-susceptible tuberculosis. However, MDR-TB is at critical levels in specific regions of the world. Hot spots for MDR-TB include Estonia, Latvia, the Oblasts of Ivanovo and Tomsk in Russia, and the provinces of Henan and Zhejiang Provinces in China. Trends confirm that MDR-TB is limited to local epidemics …’. The report added a word of caution: ‘… but the evidence is not yet irrefutable, as many countries have only provided short-term data. Two-thirds of the world’s countries and, more importantly, half of the 22 tuberculosis high-burden countries, have not yet provided data. Mathematical modelling suggests that 3.2% (or 273 000) of the world’s estimated new tuberculosis cases were MDR-TB in 2000.’

Under pressure from international non-governmental organisations (NGOs) a critical meeting in July 1999 in Boston forced the WHO to recognise the magnitude of the problem and that it was not only confined to some parts of the world.

2. DR-TB only exists in so called ‘hot spots’

In Boston the focus was still on ‘hot spots’: Latvia (727 cases nationwide), Delhi, Estonia (307 cases), some Russian Oblasts, China, and Peru (339 cases).

At this meeting the Medical Research Council (MRC) in South Africa reported that at the time there were 2 000 MDRTB patients under treatment in the country, with more than half in the Western Cape. No African countries had ever been included in ‘hot spots’ reports.

There is major epidemiological confusion between the existence of the problem and the capacity to detect it: diagnosing DR-TB requires a sophisticated laboratory to detect resistance to the drugs Rifampicin and INH, facilities that hardly existed in most African countries.

3.There is more DR-TB in Lithuania and Latvia than in South Africa

In some countries like South Africa, the TB incidence is so high because of the co-infection rate with HIV (70%) that it reaches epidemic proportions.

4. DR-TB is a man-made disaster

The WHO and The International Union Against Tuberculosis and Lung Disease have long said that most forms of DR-TB are acquired due to bad adherence by patients or system failure. A 2011 WHO report still states: ‘As drug-resistant TB is largely a man-made condition, its prevention relies heavily on the effectiveness with which control efforts succeed to treat TB patients in both the public and the private sectors. Poor treatment adherence is an important cause of emergence and spread of MDR-TB.’

This is what underpinned the WHO’s DOTS strategy of standardised treatments with quality approved drugs. Initial discovery of so-called hot spots, mostly in the former USSR, where a wide range of therapeutic strategies were used, and some bad quality drugs, reinforced the idea that DR-TB was a ‘man made disaster’ and could be corrected accordingly.

This paradigm completely ignores that HIV increases the TB transmission risk by a factor by at least 20, increasing dramatically the number of transmitted DR-TB cases in high HIV prevalence areas. In Khayelitsha, a 2008/09 survey estimated that at least 54% of DR-TB cases were transmitted and 46% acquired.

5.DR-TB is more contagious than Drug-sensitive TB (DS-TB)

There is no evidence. There are different strains in DS-TB and DR-TB and while some are originally more virulent than others (e.g. the Beijing strain), this is not primarily linked to the mutation mechanism, which might even impede the bacterial fitness to replicate.

6.DR-TB detection requires immediate infection control measures, with patient isolation in specialised

The old guidelines, still in application until 2011 in South Africa, recommended that all DR-TB cases should be referred to a centralised hospital for at least the intensive phase of treatment (six months).

Several Western countries apply severe public health measures, including legally enforced quarantine. This is partly triggered by the potential legal implications if it is proved that contamination was caused by the index case, but not by evidence.

In South Africa, the Khayelitsha decentralised pilot DR-TB project demonstrated that the time-to-treatment initiation, after a patient was diagnosed with DR-TB, was significantly reduced from 77 days to less than one week.

Infection risk drops off dramatically after treatment is started.

In South Africa, where we have a co-infection rate of 74% (meaning 74% of TB cases are infected with HIV and require urgent ART), it does not make much sense to implement a self administrated strategy for ART, where patients collect their drugs and take responsibility for being adherent) and DOTS for TB (where patients have to report daily to a health facility for their treatment).

7. DR-TB is caused mainly by poor adherence

Evidence that is now emerging that it’s not poor adherence, per se, that leads to resistance. Rather, resistance develops as a result of pharmacokinetics, drug absorption and varying drug levels in different individuals. A patient can adhere perfectly to treatment but still develop resistance to one or more drugs through treatment. HIV infection might also be related, particularly to the development of Rifampicin resistance. The simplistic and harmful approach of blaming the patient is now being proved incorrect, but unfortunately lingers.

8. DR-TB is very complex to treat and requires reference to specialist physicians

The reality is that DR-TB treatment is toxic because it re-uses old toxic drugs previously discarded for their poor efficacy and toxicity balance. Still, it is a standardised regimen that has proven to be successfully managed by Primary Health Care (PHC) nurses in integrated HIV/DR-TB PHC programmes in places like Khayelitsha.

The major challenge remains an adherence to a minimum 24-month regimen. Community-based treatment has shown better performance with regard to adherence. However, this long treatment requirement must be replaced with a new, shorter DR-TB regimen, which is in the pipeline.

9. DR-TB does not affect children

Children, and particularly children under five, are as susceptible to DR-TB as they are to DS-TB. The problem is the diagnosis of DR-TB in children. While diagnosing TB in small children is a challenge in itself, it becomes even more challenging to diagnose a resistant form of TB as the necessary bacteriological evidence such as sputum is hard to collect.

10. DR-TB presence is a barrier for TB/HIV integration at the PHC level

This misconception is based on the presumption that DR-TB cases present in the waiting room will contaminate many other patients, and even more so if they are HIV-positive. But experience has proved that integrated TB/HIV clinics have an improved diagnostic capacity for frequent atypical TB forms, while the time-to-treatment initiation is reduced. The biggest risk is based on undiagnosed – and so untreated – cases present in the waiting room and integration will actually reduce their infectiousness, dependent, of course, on universal ‘air-born’ infection control being implemented in all facilities.