A New Chapter in Tuberculosis Diagnostics

By Petra Stankard, HIV/TB Technical Advisor at PSI

In 1882, Robert Koch discovered the bacteria that caused tuberculosis (TB) and introduced sputum smear microscopy as a method for diagnosing the disease. It was a major scientific advancement. Thousands of scientific advances have followed—we’ve walked on the moon, eradicated smallpox and discovered the makeup of an atom. But until recently, in laboratories throughout the developing world, the diagnosis of tuberculosis remained firmly rooted in Koch’s discovery.

Unfortunately, smear microscopy is far from a flawless diagnostic tool. Time-consuming and cumbersome, smear microscopy often fails to detect TB in people living with HIV (one of the populations most at risk for TB disease) limiting efforts to prevent unnecessary deaths. Added to that, microscopy cannot identify whether the TB bacilli present in a smear are drug resistant. This consequently slows diagnosis and treatment of multi-drug resistant TB even as it becomes a growing health problem.

So there was cause for celebration when the story of TB diagnostics changed after more than 128 years.
The new chapter began in 2010 with the WHO’s recommendation of GenXpert MTB/RIF assay for TB diagnosis. Within two hours, this nucleic acid amplification test can identify TB in people living with HIV and determine if the TB present is resistant to rifampicin, one of the primary drugs used to treat the disease. The result is more people properly diagnosed, more people receiving the correct treatment and more lives saved.

Earlier this month, the TB diagnostics story got even better. PEPFAR, UNITAID, and the Bill and Melinda Gates Foundation announced an agreement to drastically reduce the cost of TB diagnosis using GenXpert MTB/RIF. The price of the machine’s cartridges, one of which is used for each individual tested, will drop 40% from $16.86 to $9.98.

PSI applauds the success of this partnership in extending the reach of improved TB diagnostics. This price reduction will facilitate the launch and scale-up of more programs like that of PSI/Zimbabwe. Through a partnership with the Zimbabwean Ministry of Health and Child Welfare, and with funding from TB Reach, PSI has introduced GenXpert MTB/RIF technology in its franchise HIV testing and counseling centers in Harare and Bulawayo. GenXpert technology has increased the detection of TB in HIV positive people with TB symptoms by 10% as compared to smear microscopy alone. As a result, more individuals are accessing the treatment they need to lead healthy lives.

There still remains much to be written in this story. Research into cheaper and simpler point-of-care TB diagnostics is growing and opportunities to further reduce the cost of Xpert MTB/RIF remain. PSI looks forward to the growth of these innovations and to continued partnerships to bring new TB diagnostics to scale and improve the lives of the people we serve.