Blood Test Can Identify Those at Risk of Developing TB, Study Finds

A new blood test being developed in the United Kingdom has been shown to not only identify those infected with human tuberculosis (TB) but also identify those most at risk of developing it.

Researchers publishing in the journal Clinical Infectious Disease reported in late June on their work on a high sensitivity assay called Actiphage, which looks for the presence of the bacteria that causes Mycobacterium tuberculosis (MTB). The study involving 66 people took place at the National Institute for Health Research Leicester Biomedical Research Centre and the University of Nottingham's School of Biosciences.

Participants were divided into 4 groups: people with active pulmonary TB, with latent TB, a control suspected to have TB but who did not have it, and a healthy control group. All patients were tested twice, 12 months apart.

Actiphage recorded a positive result in 73% of those who were later diagnosed with TB, a rate that researchers said was higher than expected for an experimental study. No one in the control groups tested positive with the assay, and no one with latent TB tested negative and went on to develop active TB. The researchers reported that 2 of 3 people with latent infection who tested positive developed TB more than 6 month after taking the test, which suggests its potential predictive value.

"TB is the leading cause of death from an infectious disease,” Pranabashis Haldar, MRCP, clinical senior lecturer at the University of Leicester and consultant in respiratory medicine at its hospitals, said in a statement.

Haldar said the disease most often affects the lungs and spreads through coughing and sneezing. “As there is a lack of diagnostic tools for people unable to bring up sputum, diagnosis is delayed, increasing the likelihood that the disease is spread,” he said.

Researchers said roughly one-fourth of the world’s population carry the infection as latent TB, and the way in which it moves to active TB is not well understood. Insights from this new study show that there is a “transitional” phase, called incipient TB, which the Actiphage test can catch through screening programs in patients unable to produce sputum, including children.

“The new Actiphage blood test offers the potential to target those at risk of TB and allow treatment to start early. This is a very exciting development that invites further study,” he said.

Reference

Verma R, Swift BMC, Handley-Hartill W, et al. A novel high sensitivity bacteriophage-based assay identifies low level M. tuberculosis bacteraemia in immunocompetent patients with active and incipient TB [published online June 22, 2019]. Clin Infect Dis doi.org/10.1093/cid/ciz548.