LMU researchers evaluate host-response test for tuberculosis in high-risk household contacts in Africa

Household contacts of people with tuberculosis (TB) have a high risk of getting TB themselves, at around 2 percent. It is currently difficult to detect TB in its early stages, or predict who will go on to have TB, and therefore preventive treatment is not widely used. Most contacts are asymptomatic and current approaches rely mainly on symptom-based screening and sputum testing, which often miss early or hidden disease. As a result, many infections are only identified once the disease has progressed.

A study published in The Lancet Infectious Diseases by LMU scientists Professor Katharina Kranzer, Dr Norbert Heinrich, and colleagues within the ERASE-TB consortium explores a different approach: host-response assays. The researchers assessed whether a blood-based 3-gene host-response test can detect active tuberculosis and help predict future disease. Unlike standard tests that detect the bacteria directly, these assays measure the body’s immune response, which may allow earlier identification of infection and people at higher risk of disease.

Large-scale study in African households

In a large prospective study funded by the European and Developing Countries Clinical Trials Partnership (EDCTP2), the team evaluated the Cepheid Xpert MTB Host Response (MTB-HR) blood test in more than 2,000 household contacts in Tanzania, Zimbabwe, and Mozambique. Participants aged 10 years and older were followed for up to two years with regular clinical, imaging, and laboratory assessments. At each visit, a finger-prick blood sample was analysed using the GeneXpert platform.

The MTB-HR assay showed good accuracy for detecting active tuberculosis and was able to distinguish well between individuals with and without disease. Its ability to predict future disease was moderate, performing best shortly before disease onset but less precise when predicting TB onset longer in the future. The test’s positive predictive value for incident was higher than that of currently used immunological tests, although overall it did not meet WHO criteria as a stand-alone screening or predictive tool.

Improving the effectiveness of tuberculosis prevention

The findings suggest that immune-based tests may help both to detect active tuberculosis and to identify people who are at risk of developing the disease in the future. The researchers highlight that household contacts are often asymptomatic at the time of screening, despite potential infection. Current standard tests have limited ability to predict who will progress to active disease.

Overall, the study provides important evidence that host-response assays could contribute to more targeted screening and prevention strategies, potentially reducing unnecessary preventive treatment and improving the efficiency of tuberculosis control efforts. At the same time, the researchers underscore the importance of assessing such tools in the real-world settings where they are intended to be used.