AN EXCEPTIONALLY sensitive blood test for the diagnosis of tuberculosis (TB) has been developed by researchers from Tulane University School of Medicine, New Orleans, Louisiana, USA. This novel blood test is utilised for screening DNA fragments for Mycobacterium tuberculosis bacteria and will enable doctors to speedily identify TB and determine suitable treatments by observing the level of Mycobacterium tuberculosis bacteria DNA in the bloodstream.
According to the World Health Organization (WHO), approximately 10 million people have contracted TB, and of those, 1.5 million people died from the disease. Worldwide TB is the 2nd most life-threatening infectious disease, with COVID-19 being the first. Most of the tests for TB rely on sputum screening; however, this methodology is challenging particularly in children. Furthermore, in patients with weakened immune systems, such as patients with HIV, the TB bacteria migrate from the lungs to other parts of the body. Therefore, the bacteria in the sputum in these patients who are immunocompromised will be scarce thus providing inaccurate results with the sputum screening methodology for TB diagnosis.
The study used a clustered regularly interspaced short palindromic repeats (CRISPR) based assay that targets cell-free DNA from live Mycobacterium tuberculosis bacilli, which then was released into the bloodstream. The CRISPR method requires a small blood sample and provides results in a short period of time (less than 2 hours). The researchers tested this on preserved blood samples from 73 adults and children, from Eswatini, speculated to have TB. The sensitivity (positive test) and specificity (negative test) of the blood test were documented by the researchers. The results showed a sensitivity of 96.4% and 83.3% in adults and children, respectively. The specificity results from the test were 94.1% in adults and 95.5% in children. Additionally, the researchers tested 153 blood samples from a cohort of hospitalised children diagnosed with HIV and with an elevated risk of contracting TB. The novel test identified 13 confirmed cases of TB and a further 85% of patients with unconfirmed TB diagnoses.
“We are particularly excited that the level of Mycobacterium tuberculosis cell-free DNA in children with HIV began to decline within a month of treatment, and most of the children’s blood was cleared of the bacteria DNA fragments after treatment, which means that CRISPR-TB has the potential to monitor treatment and will give physicians the ability to better treat worldwide TB infections,” lead study author Tony Hu, Weatherhead Presidential Chair in Biotechnology Innovation at Tulane University, New Orleans, Louisiana, USA.