It’s 30 years since the World Health Organisation identified the resurgence of tuberculosis as a global public health emergency, an issue reiterated by its present head. TB drug resistance underlines the need to collaborate on diagnostic provision, urges Ruth Brignall.
In 2021, it was estimated that nearly 10.6 million people fell ill with tuberculosis (TB) and nearly 40% of them did not receive access to healthcare services.
The Director-General of the World Health Organisation (WHO), Dr Tedros Ghebreyesus, has recently called for joint action between communities and health systems to bring TB under control. To support these efforts WHO launched a new flagship initiative to End TB. In the UK, after a steady decline in TB cases over the past years, recent data suggests that progress seems to have stalled. There is now a need for immediate action for the UK to meet international targets outlined as per the WHO’s End TB Strategy.
Vulnerable populations – including prisoners, migrants and socially marginalised people – are particularly at risk because of the increased exposure associated with their living conditions. People living with HIV or suffering from other conditions that weaken the immune system, such as diabetes, are especially vulnerable because this greatly increases their risk of developing the disease. Children are also vulnerable because of their weaker immune systems.
It is critical that everyone has access to timely diagnosis and treatment of TB, but fear and stigma associated with the disease, as well as drug resistance, remain significant challenges despite TB being a preventable disease.
However, significant developments in TB diagnosis do provide some hope. We predominantly see two forms of TB – active and latent. The TB bacteria, Mycobacterium tuberculosis, can remain in the body without causing sickness and many people who have latent TB infection never develop TB disease. In these people, the TB bacteria remain inactive for a lifetime without causing disease. But in other people, especially people who have a weak immune system, the bacteria can become active, multiply and cause TB disease.
There are different diagnostic tools and modalities available for the diagnosis and treatment of active and latent TB. TB antigenspecific skin tests (performed and resulted in the clinic over two patient visits) and interferon gamma release assays (IGRA, performed in the lab and requiring only one patient visit for blood collection) mean that latent TB can be detected and treated before people develop the symptoms associated with active disease.
Latent TB can be detected and treated before people develop the symptoms associated with active disease
Increased use of IGRAs in recent years has been acknowledged by the WHO, with the inclusion in their essential diagnostics list. However, not all IGRAs are the same and the WHO operational handbook on tuberculosis states that ELISA (enzyme-linked immunosorbent assay) based tests can be affected by pre-analytical variables, whereas the additional normalisation step before cell stimulation required in tests like the T-SPOT. TB test can mitigate the impact of pre-analytical variables. This may make it a more suitable test, particularly in immunosuppressed and peadiatric patients. This in vitro test from Oxford Immunotec is used by the NHS to diagnose latent TB in a number of different settings.
In terms of diagnosing active TB, one of the main focuses remains identifying strains of TB that may not respond to traditional drug treatments. Drug resistance is a growing issue that threatens TB care worldwide, and developments in diagnostics mean that many of these resistant strains can be accurately identified. However, the challenge now is to ensure these diagnostics can be made available on a global scale; they need to provide rapid, accurate and cost-effective results in settings where power, equipment and technical expertise may be limited.
With TB now the second most deadly infectious disease in the world after Covid-19, furthering our progress towards eliminating it needs urgent attention.
Given the preventable nature of the disease, governments and healthcare systems must make greater efforts to strengthen prevention and awareness programmes to encourage screenings and help in the timely detection of TB. Collaboration is critical in meeting this challenge head-on and, together, we can – and have a pressing responsibility to – finally end TB.
- Ruth Brignall, PhD, is Global Scientific Affairs Manager at Revvity (formerly Perkin Elmer)