A new tuberculosis (TB) test disclosed in the Association for Diagnostics & Laboratory Medicine’s (formerly AACC’s) Clinical Chemistry journal would allow testing for TB treatment monitoring to occur outside of a biosafety level 3 (BSL-3) laboratory. This could help reduce worldwide mortality from TB by enabling low- and middle-income countries that lack BSL-3 facilities to treat TB more efficiently.
A team of researchers designed this test — called rapid enumeration and diagnostic for tuberculosis (READ-TB) — specifically to address lack of access to labs that meet BSL-3 requirements. This novel test determines how patients are responding to TB treatment. With READ-TB, sputum — thick mucus coughed up from the lungs — is treated with acetic acid, a chemical that kills bacteria but leaves bacterial RNA intact. A laboratory professional can then safely feed the RNA into a machine that measures RNA concentration, which is an indicator for how much Mycobacterium tuberculosis a patient is carrying and how the infection is responding to treatment.
Compared to guanidium salts, the class of chemicals currently considered the gold standard for preserving RNA, acetic acid was more effective at killing sputum bacteria, doing so in just 30 minutes, which eliminates the need for a BSL-3 laboratory. Acetic acid was also just as effective as guanidium salts in preserving bacterial RNA. Notably, the researchers found that RNA was preserved in acetic acid for 14 days when kept at 25°C, and for at least 1 year when kept at –20°C.
This is an important advantage for laboratories that lack –70°C freezers, which require a much greater amount of energy. Additionally, guanidium salts are toxic, while the concentration of acetic acid used for READ-TB is much safer to work with.