New Developments in the Laboratory Diagnosis of Tuberculosis: New and Faster Ways of Diagnosing Tuberculosis are Needed Urgently

Although the incidence of tuberculosis (TB) has declined in many regions of the world over the past decade, absolute numbers of cases continue to increase, with 9.27 million new cases diagnosed in 2007. (1) Africa is particularly affected, with the incidence and mortality both rising steadily, owing, at least in part, to the deadly synergy between TB and HIV. TB control programmes still rely primarily on smear microscopy for diagnosis--a technique that has remained essentially unchanged for the past 100 years, although the introduction of fluorescent acid-fast staining for smear microscopy has reduced operator time and resulted in a modest increase in sensitivity. Incremental advances in culture technology have also been made in the past decades, including the introduction of liquid culture and automated systems for detection of mycobacterial growth. This has significantly reduced time to detection--from an average of 20-24 days to 10-12 days. However, culture results are still frequently received too late to have an impact on clinical management. Moreover, culture remains cumbersome and costly, involving decontamination and concentration of sputum, which requires bio-safety level 3 facilities, expensive equipment and highly trained personnel. These facilities are often not available in high-burden regions. There is therefore an urgent need for more rapid and sensitive diagnostic tests for TB.