The study highlights that in order to End TB and break the cycle of infection there is an urgent need for tests able to detect disease progression in those without clinical symptoms.
TB is predominantly transmitted by a coughing, which is seen as a key symptom of the disease, but probably also through simply breathing.
Findings reveal reservoir of undiagnosed disease
“We already knew that there was a giant gap between the 10.6 million who get ill with tuberculosis and the 7.5 million cases that were registered by health authorities in 2022.” says Frank Cobelens, Professor of Global Health at Amsterdam UMC and Senior Fellow at the AIGHD.
“A persistent cough is often the entry point for a diagnosis, but if 80% of those with TB don’t have one, then it means that a diagnosis will happen later, possibly after the infection has already been transmitted to many others, or not at all,”
“Our results indicate the probable reason why, despite huge efforts to diagnose and treat the disease, the tuberculosis (TB) burden across Africa and Asia is hardly declining.
The Research, led by Amsterdam UMC and the Amsterdam Institute for Global Heath and Development, analysed data on more than 600,000 individuals in Africa and Asia and found that 82.8% of those with tuberculosis had no persistent cough and 62.5% had no cough at all. These results are published (12 March 2024) in the Lancet Infectious Diseases.
Quarter of those with TB had no persistent cough or other symptoms
The study analysed the results of national monitoring schemes in 12 countries, and found that, alongside the lack of a cough, more than a quarter of those with TB had no symptoms at all. With both of these traits being more common in women than in men. Further, the study showed that a quarter of those without cough have high loads of bacteria in their sputum and are probably highly infectious.
“When we take all of these factors into account, it becomes clear that we need to really rethink large aspects of how we identify people with TB. It’s clear that current practice, especially in the most resource-poor settings will miss large numbers of patients with TB. We should instead focus on X-ray screening and the development of new inexpensive and easy-to-use tests” says Cobelens.
Urgent need for TB diagnostic to provide early indication of disease progression
PBD Biotech is developing a phage-based diagnostic, Actiphage TB, that can detect the pathogen that causes TB in the blood – providing early indication of disease progression before clinical symptoms occur.
The Actiphage diagnostic is currently in clinical trials led by Dr Pranabashis Haldar, clinician and Principal Investigator in the Respiratory and Infection Theme of the Leicester NIHR Biomedical Research Centre, UK.
Dr Haldar says that the Amsterdam UMC study is significant; “The lack of classical symptoms of TB – cough etc does not mean that patients classed as subclinical are not infectious, In fact the requirement of a cough for diagnosis likely misses this hidden population of cases contributing to the spread of infection and adding to the burden of disease in high prevalence countries.”
The Lancet Infectious Diseases: Prevalence of subclinical pulmonary tuberculosis in adults in community settings: an individual participant data meta-analysis
DOI: 10.1016/S1473-3099(24)00011-2
