New blood test called Actiphage can identify people with latent TB infection at risk of developing the disease
A new blood test called Actiphage has shown the potential to not only diagnose human tuberculosis (TB) but also identify those at most risk of developing the disease, according to findings published in the medical journal Clinical Infectious Diseases.
TB is a serious bacterial infection, which can be life threatening if not properly treated with antibiotics. Pulmonary TB of the lungs or throat is contagious although TB can affect any part of the body.
The research, carried out at the National Institute for Health Research (NIHR) Leicester Biomedical Research Centre (BRC) and the University of Nottingham’s School of Biosciences, used new blood test called Actiphage to look for the presence of the bacteria that cause TB (Mycobacterium tuberculosis or MTB). The study involved 66 participants in four groups: those with active pulmonary TB, those with latent TB, a control group of patients referred for suspected TB but found not to have the disease, and a control group of healthy individuals.
TB continues to be India’s severest health crisis. TB kills an estimated 480,000 Indians every year and more than 1,400 every day. India also has more than a million ‘missing’ cases every year that are not notified and most remain either undiagnosed or unaccountably and inadequately diagnosed and treated in the private sector.
TB kills an estimated 480,000 Indians every year andmore than 1,400 every day. India also has more than a million ‘missing’ cases every year that are not notified and most remain either undiagnosed or unaccountably and inadequately diagnosed and treated in the private sector
The new blood test was used to test all of the patients twice, 12 months apart. Actiphage tested positive in 73 per cent of people that we subsequently diagnosed with TB. None of the participants in the control groups tested positive with Actiphage and none of the patients with latent TB who tested negative with Actiphage went on to develop active TB.
Intriguingly, two of the three participants with latent TB infection who tested positive with Actiphage went on to develop the disease more than six months later, suggesting the test may have a predictive role in identifying people with the infection at risk of developing the disease.
Dr Pranabashis Haldar, Clinical Senior Lecturer at the University of Leicester and Consultant in Respiratory Medicine at Leicester’s Hospitals and senior author of the paper, said: “TB is the leading cause of death from an infectious disease. It most commonly affects the lungs and from this site is transmitted to others by 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.”
Around a quarter of the world’s population carry the infection. In the vast majority, this is in the form of latent TB, which does not affect their health, but carries a risk of progressing to the active form of TB in around ten per cent of those infected. The mechanism for this is poorly understood.
Dr Haldar continued: “As a blood test, it is particularly suitable for patients unable to produce sputum, including children, and may help support diagnosis in underserved groups that struggle to access freely available healthcare resources.”
The new Actiphage test was developed primarily as a blood or milk test for bovine TB and Johne’s disease can be completed in as little 6 hours.
Study co-author Dr Catherine Rees, Associate Professor in Microbiology at the University of Nottingham and Chief Scientific Officer at PBD Biotech, said: “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.”
