Wanted: Continued development of TB diagnostics to reduce antimicrobial resistance

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McGillScience Speaks staff writer and Global Health Policy Research Coordinator Rabita Aziz is attending and writing from McGill Summer Institute in Infectious Diseases and Global Health this week.

MONTREAL — New diagnostic technology for tuberculosis still is needed not only for TB control, but to combat growing antimicrobial resistance, Dr. Madhukar Pai said here this week.

An affordable, easy-to-use test that could diagnose the disease as well as gauge its resistance to the drugs used to treat it, used in health settings, would lead to the reduced yet correct use of antibiotics to treat TB, less money being spent on treatments and contribute to more sustainable health systems, Pai, who is director of McGill University’s global health program, said.

Of the nine million cases of tuberculosis globally, he said, three million “are not on anyone’s radar,” going either undiagnosed or unreported to national TB programs.

Many patients who are diagnosed – only after the weeks it can take to diagnose through sputum smear microscopy – are immediately placed on a cocktail of antibiotics, including second-line drugs, because health care providers don’t know if there’s antibiotic resistance and don’t want to risk it, Pai said. This method, he said, leads to more antibiotic resistance.

The GeneXpert rapid diagnostic test was supposed to help with that, Pai said, but at nearly $10 a cartridge, most low- and middle-income countries can’t afford making it a part of standard tuberculosis care. Those countries are used to spending less than one dollar on sputum-smear microscopy, he said.

Even with the price tag, more than 16 million GeneXpert cartridges have been procured by 180 countries, he said. In the 22 highest burden countries, by contrast, more than 77 million smears are performed annually.

And microscopy diagnosis remains challenged, Pai said, with many diagnostic labs in the developing world having “no continuous power, no temperature control, no centrifuge, no hood to work under – all they have is a mobile phone.”

The answer, he said, is to stop treating diagnostics as the “ugly step child of global health,” and develop easy-to-use, point of care, rapid diagnostics that would lead to patients getting the treatment they need while preventing antimicrobial resistance.

“If you can develop a fabulous test for Ebola in two years,” he said, “why the hell isn’t there a diagnostic for TB after 100 years?”

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