A study led by the University of Cape Town (UCT) has found that most tuberculosis (TB) cases detected among adults living with someone who has TB are silent (without symptoms) at the time of screening.
The study, published in The Lancet Global Health, suggests that to slow the spread of TB, South Africa and other high-burden countries should bring TB tests into communities and offer them to people at higher risk – such as household contacts – even if they feel well.
Dr Simon Mendelsohn, lead author of the study and senior researcher at UCT’s South African Tuberculosis Vaccine Initiative (SATVI), says that most people are tested for TB only after they develop symptoms (such as a prolonged cough) and visit a clinic.
He explains: “National surveys also decide who gets a sputum test by first checking for symptoms or doing a chest X-ray. This new study shows that those approaches miss many people with TB, especially those who don’t yet feel sick. Very few studies test every participant regardless of symptoms or chest X-ray findings to see how much silent TB we’re missing.”
Researchers from the RePORT South Africa Network, led by scientists from SATVI – an initiative based in UCT’s Institute of Infectious Disease and Molecular Medicine – visited households in three South African communities and offered sputum lab tests to all adult contacts of people with TB – even if they had no symptoms or normal chest X-rays.
The team found that about 80% of people with TB had no symptoms, and more than half of these had chest X-rays that did not show evidence of active disease – yet they could still potentially spread TB.
“In short, relying on symptoms or X-rays alone means many infectious people are not being found and treated early,” says Dr Mendelsohn. “We are not detecting TB early enough and mostly treating people with more advanced disease who self-present to the clinic. If we want to cut transmission, we need to find TB earlier – by going into communities and offering tests before people recognise their symptoms.”
The researchers recommend the following actions:
- Take testing to people: Add household-level, community testing for contacts of TB patients and other high risk groups – even when they feel well.
- Update screening playbooks: Programmes that use symptoms and X-rays alone could build in simple microbiological tests so fewer people with TB are missed.
- Measure the real burden: National TB surveys should include universal sputum testing in contacts and other high risk groups to avoid undercounting silent TB.