ABSTRACT

I. Introduction The continuing epidemics of HIV-associated tuberculosis (TB) and multidrug-resistant (MDR) TB have radically changed thinking on the need for new TB control tools. The much-publicized outbreak of extensively drug-resistant (XDR) TB among HIV-infected patients in KwaZulu-Natal, South Africa, in 2006 with rapid progression of disease and high mortality (1) has accelerated this process, pointing to the urgent need for rapid drug-susceptibility testing (DST) integrated into TB control programs. Earlier it had been widely assumed that the most commonly available diagnostic tool, acid-fast bacillus (AFB) microscopy, when properly applied was sufficient for the diagnosis of the most infectious cases, who often were also critically ill and in need of treatment. In addition, it was thought that TB treatment services should be strengthened before increasing case finding in order to avoid the creation of a large pool of poorly treated, potentially drugresistant cases. Thus, the diagnostic focus of the World Health Organization (WHO) DOTS strategy was appropriately on improving the quality of smear microscopy through training and quality assurance programs.