A new study provides an ultra-sensitive detection of tuberculosis in blood using CRISPR. Published in The Lancet Microbe, the optimised method could offer an early, rapid and accurate test, ensuring people don’t go undiagnosed and instead receive the treatment they need.
Tuberculosis remains a leading cause of global mortality. There are an estimated 10 million people diagnosed with tuberculosis and 1.2 million tuberculosis-related deaths annually.
Sputum-based assays are typically used for diagnosing tuberculosis, but this technique is less effective in adults and children living with HIV as it is difficult to collect respiratory samples.
Alternative rapid diagnosing options need to be developed to help tuberculosis patients. Furthermore, improved tuberculosis treatment monitoring is needed to evaluate treatment responses.
CRISPR-TB successfully identifies tuberculosis
An optimised CRISPR-mediated tuberculosis (CRISPR-TB) assay was used to detect Mycobacterium tuberculosis cell-free DNA (Mtb-cfDNA) in patients’ serum.
The molecular diagnostics study used data from Eswatini and Kenyan populations. Patient populations included adults and children with presumptive tuberculosis and their asymptomatic household contacts. Samples were taken at enrolment and during tuberculosis treatment up to 24 weeks later.
CRISPR-TB identified microbiologically and clinically confirmed tuberculosis cases in the Eswatini adults with 96% sensitivity and 83% sensitivity in the Eswatini child cohort. Notably, CRISPR-TB identified all six extrapulmonary tuberculosis cases (lymph node, bone, joint, and pleura involvement) in this group.
Furthermore, in the Kenyan cohort of children living with HIV, CRISPR-TB identified 100% of confirmed tuberculosis cases. The method also identified 85% of otherwise unconfirmed tuberculosis cases, suggesting that current microbiological diagnosing methods are underdiagnosing children.
Intriguingly, Mtb-cfDNA was detected in serum collected from children living with HIV weeks before their diagnosis with tuberculosis by other methods. This suggests the method could open doors for early diagnosis.
Looking to the future
CRISPR-mediated detection of circulating Mtb-cfDNA shows promise to increase the identification of tuberculosis and holds potential for early diagnosis and rapid monitoring of tuberculosis treatment responses.
Researchers observed that Mtb-cfDNA concentrations rapidly decreased following the start of tuberculosis treatment. This holds potential for tuberculosis treatment monitoring.
In this study, baseline Mtb-cfDNA concentrations in children living with HIV admitted to hospital tended to correspond with increased mortality. This suggests that Mtb-cfDNA positivity could predict short-term mortality in this population, particularly in the absence of tuberculosis treatment, but further studies are needed.
The authors note, “These findings highlight potentially high-impact applications, including early tuberculosis diagnosis and identification of children at increased risk of tuberculosis-related mortality.”
Written by Poppy Jayne Morgan, Front Line Genomics
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