To slow the spread of tuberculosis (TB) and enable early detection of infectious cases in South Africa and other high-burden countries, it’s crucial to take testing directly into the community. This will help people at high risk of infection, especially those who share a living space with TB patients and are asymptomatic, suggests a team from the University of Cape Town.
According to their recent study, published in The Lancet Global Health, testing these household contacts, even if they don’t feel unwell, is critical.
This comes after research revealed that most TB cases detected among adults living with someone who has TB were silent at the time of screening.
The study’s lead author and a senior researcher at UCT’s South African Tuberculosis Vaccine Initiative (SATVI), Dr Simon Mendolsohn, said most people are only tested for TB after they present with symptoms like a prolonged cough. And this needs to change.
“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,” he said. “Very few studies test every patient regardless of symptoms or chest X-ray findings to see how much silent TB we’re missing.”
Detection not happening early enough
As part of this study, researchers from RePORT South Africa Network – a research consortium focused on infectious diseases, headed by scientists at SATVI – visited households in three South African communities and offered sputum lab tests to all adults who had been in contact with people with TB, even if they were asymptomatic or presented with a normal chest X-ray.
The research found that 80% of participants with TB were asymptomatic. More than half of this group of responders also presented with chest X-rays that showed no traces of active disease. Yet, they were probably spreading the disease.
To locate these patients, he said researchers recommend adopting a three-point plan:
• Take testing to the 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 that 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.
“In short, relying on symptoms or X-rays alone means many infectious people are not being found and treated early. 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,” Mendelsohn said.
Study details
Screening for asymptomatic tuberculosis among adults with household exposure to pulmonary tuberculosis: a prospective observational cohort study
Simon Mendelsohn, Humphrey Mulenga, Michele Tameris, Tumelo Moloantoa, Stephanus Malherbe, Austin Katona et al.
Published in The Lancet Global Health in November 2025
Summary
Background
More than half of tuberculosis cases detected by community prevalence surveys are classified as asymptomatic. We evaluated yield of symptom and chest radiograph screening of tuberculosis-exposed household contacts in South Africa.
Methods
For this prospective observational cohort study, adult volunteers (aged ≥18 years) with household exposure within the past 6 months to patients with untreated or partially treated pulmonary tuberculosis, identified through local health services, were enrolled at three sites in South Africa (Worcester and Ravensmead, Western Cape Province, and Soweto, Gauteng Province). Household contacts were excluded if they were unlikely to attend study visits, or had conditions interfering with consent or study participation, including psychiatric illness, substance dependence, or incarceration. Systematic screening of tuberculosis symptoms (any duration), chest radiograph (any abnormality indicative of active tuberculosis), and sputum microscopy, Xpert Ultra, and liquid culture were performed. Serum C-reactive protein (CRP) was measured by multiplex bead array. Prevalent tuberculosis was microbiologically confirmed (Xpert Ultra or culture). Symptomatic and asymptomatic tuberculosis were defined as prevalent tuberculosis with and without reported symptoms compatible with tuberculosis. The primary outcome was the diagnostic yield (sensitivity) of microbiologically confirmed pulmonary tuberculosis.
Findings
Between April 22, 2021 and Sept 22, 2022, 979 household contacts were enrolled, 345 (35·2%) male and 634 (64·8%) female, 185 (18·9%) living with HIV and 187 (19·1%) with previous tuberculosis. Prevalent tuberculosis occurred in 51 (5·2%) and was asymptomatic in 42 (82·4%) of 51. Only 13 (31·0%) of 42 asymptomatic people with tuberculosis were sputum-smear positive; eight (61·5%) of these 13 had a low bacillary burden, with smear grades scanty or 1+ (1–99 acid-fast bacilli per 100 fields). CRP did not discriminate healthy household contacts from those with asymptomatic tuberculosis (area under the curve 0·60, 95% CI 0·47–0·73). An abnormal chest radiograph suggestive of tuberculosis was observed in 23 of 41 asymptomatic (sensitivity 56·1%, 95% CI 41·0–70·1) versus eight of nine symptomatic (sensitivity 88·9%, 56·5–98·0) people with tuberculosis. Sensitivity of chest radiograph in combination with symptom screening was 32 (64·0%) of 50 (50·1–75·9) for all prevalent tuberculosis.
Interpretation
More than 80% of confirmed people with tuberculosis among household contacts were asymptomatic; chest radiograph screening missed more than 40% of these. Community prevalence surveys reliant on symptom-based and chest radiograph-based approaches might substantially underestimate the prevalence of asymptomatic tuberculosis in endemic countries.
See more from MedicalBrief archives:
SA and Indonesia collaborate on asymptomatic TB study
Most TB patients don’t have persistent cough – global study
Digital X-rays increase TB detection in asymptomatic South Africans