Failure of Directly Observed Treatment Strategy (DOTS): A Setback on “Stopping TB in My Lifetime”?
Tuberculosis (TB) is one of the major healthcare problems faced by many developing countries across the globe. After the pandemic of HIV, it’s being seen in increasing incidence in the developed countries as well. According to the data published by World Health Organization (WHO), in the Year 2010, there were 8.8 million (range, 8.5–9.2 million) deaths reported from 198 countries among HIV-negative patients while 0.35 million (range, 0.32–0.39 million) deaths from HIV-associated TB patients.
In 2010, 5.7 million new cases of TB were reported. India and China accounted for 40% and Africa for another 24%. Its note worthy that only 22 countries share 82% of the global burden of the TB cases. In 2009, 87% of the pulmonary TB patients with smear positive status were treated successfully to smear negative, hence depicting the success in the treatment.
Pulmonary TB is the most common form of TB. The primary treatment regimen comprises four drugs namely, Isoniazid, Rifampin, Pyrazinamide, and Ethambutol for the first two months and then Rifampin and Isoniazid for the next four months. Lack of compliance and affordability of the TB drugs have been attributed to the failure in the treatment which lead to the development of Multi Drug Resistant TB (MDR-TB), defined as resistance to either Isoniazid or Rifampin. To overcome the problem of compliance, WHO initiated Directly Observed Treatment Strategy (DOT or DOTS) in 1995 for controlling TB. During the period of 1995 to 2010, a total of 55 million TB patients were treated under DOTS guidelines and 46 million were cured.
However, despite the vigor of DOTS, a new strain Extensively Drug-Resistant Tuberculosis (XDR-TB) has emerged. XDR-TB is resistance to any one of inject-able drug and any one of drug from the Quinolones. Repeated treatment strategy failures have led to the worse form of TB in the recent times, despite the successful application of DOTS.
In spite of the so called effective therapeutic strategies such as DOTS, more than 8 million people die of TB every year. A famous systematic review by Volmink J and Garner P, published in 2007 at the Cochrane Database, compared self administration of anti tuberculosis drugs versus DOT options for the patients for treating active or latent TB. The study included eleven randomized and quasi-randomized controlled trials with 5609 participants from low, middle and high income countries. There was no significant difference between DOTS and self administration for cure (RR 1.02, 95% CI 0.86 to 1.21). Moreover, there were similar results for cure with completion of the therapy. It is interesting to note that DOTS at home had a little more benefit than DOTS at clinics in terms of cure (RR 1.10, 95% CI 1.02 to 1.18).
Earlier this year, Azhar GS (Lung India. 2012 Apr-Jun; 29(2): 147–153) studied DOTS for TB relapse from India, a country which contributes to a major proportion of TB cases reported worldwide. He included seven trials and concluded that the relapse rate under DOTS treatment defined as relapse in first six months was more than 10%, which is higher than the studies from other countries.
From the available literature, it is obvious that DOTS has been in-effective in reducing the TB relapse, hence not fulfilling our expectations. “Stopping TB in My Lifetime”, the WHO’s TB slogan for 2012 will merely be a dream unless new effective strategies are developed to fight one of the worst infectious killer of mankind.