New TB test promises to be cheap and quick

Researchers have come up with a microfluidic chip to test for latent tuberculosis. They hope that the test will be cheaper, faster and more reliable than the current one. Biomedical engineers at UC Davis claim that the test can be reused as well. "Our assay is cheaper, reusable, and gives results in real time," said Ying Liu, a research specialist working with Professor Alexander Revzin in the UC Davis Department of Biomedical Engineering. The team has already tested blood samples from patients in China and the United States. According to the US Centres for Disease Control and Prevention, about one-third of the world`s population is infected with the bacteria that cause tuberculosis, a disease that kills an estimated 1.5 million people worldwide every year. Most of the infected people have latent TB, in which the bacteria are kept in check by the immune system. And patients become sick only when the immune system is compromised, enabling the bacteria to become active. People with HIV are especially at a high risk.Available tests for latent TB are based on detecting the interferon-gamma, a disease-fighting chemical made by cells of the immune system. Moreover, commercially available tests require sending samples to a lab, and can be used just once. Liu and Revzin used a novel approach by coating a gold wafer with short pieces of a single-stranded DNA segment known to stick specifically to interferon-gamma. Then they mounted the wafer in a chip that has tiny channels for blood samples. If interferon-gamma is present in a blood sample, it sticks to the DNA, triggering an electrical signal that can be studied by a clinician. "If you see that the interferon-gamma level is high, you can diagnose latent TB," Liu said. The researchers plan to improve the system so that the microfluidic sensor and electronic readout are integrated on a single chip. A patent application has been filed for the technology, and the researchers hope the test can be commercialized after the approval from FDA.