Lancet study reveals chest X-rays miss 40% of asymptomatic TB cases, with 82% of infected household contacts showing no symptoms, challenging current screening methods.
TB Detection Crisis:
Why Chest X-Rays Miss 40% of Silent Infections
Study screened 979
household contacts in South African communities using universal testing
5.2% of contacts had
pulmonary TB with 82.4% showing no symptoms
Chest X-rays detected
only 56.1% of asymptomatic tuberculosis cases
Combined symptom and
X-ray screening reached just 64% sensitivity, below WHO standards
Commonly used chest
X-rays, based on symptoms, are inadequate to detect asymptomatic tuberculosis
(TB) infection among household contacts, according to a study published in the
journal The Lancet Global Health.
"More than 80
per cent of confirmed people with tuberculosis among household contacts were
asymptomatic; chest radiograph screening missed more than 40 per cent of these
- Dr Simon C Mendelsohn"
Researchers from the
University of Cape Town, South Africa, conducted systematic screening with
universal sputum microbiological testing of 979 household contacts of people
with pulmonary tuberculosis in three South African communities.
They compared
tuberculosis symptom (any duration) and chest radiograph (any abnormality
indicative of active tuberculosis) screening approaches against a microbiological
reference standard.
The team confirmed
pulmonary tuberculosis in 5·2 per cent of household contacts, and 82·4 per cent
of these reported no symptoms. Alarmingly, the chest radiographs were not able
to detect 40 per cent of the cases.
"More than 80
per cent of confirmed people with tuberculosis among household contacts were
asymptomatic; chest radiograph screening missed more than 40 per cent of
these," said corresponding author Dr Simon C Mendelsohn, South African
Tuberculosis Vaccine Initiative, at the varsity.
"Community prevalence
surveys reliant on symptom-based and chest radiograph-based approaches might
substantially underestimate the prevalence of asymptomatic tuberculosis in
endemic countries," he added.
According to the
World Health Organization (WHO), approximately 2·7 million (25 per cent) of the
estimated 10·8 million people with tuberculosis worldwide went undiagnosed or
untreated in 2023.
While finding and
treating these so-called missing millions is crucial, the challenge is that a
majority of these remain asymptomatic.
"More than half
of all tuberculosis found in community prevalence surveys has been classified
as asymptomatic, occurring in people who do not have, recognise, or report
typical tuberculosis symptoms such as cough, fever, night sweats, and loss of
weight," the team said in the paper.
In the study,
asymptomatic tuberculosis in household contacts had low bacterial load, and
were also associated with low serum C-reactive protein concentrations that were
indistinguishable from those of healthy controls. However, these were distinct
from symptomatic tuberculosis in a comparator group of clinic attendees.
Sensitivity of chest
radiograph screening for asymptomatic tuberculosis was only 56·1 per cent;
sensitivity of combined symptom and chest radiograph screening for all
tuberculosis was marginally higher at 64·0 per cent.
"Our findings
from household contacts suggest that symptom-based and chest radiograph-based
approaches are inadequate for community tuberculosis screening and do not meet
the WHO target product profile for a tuberculosis screening test (minimum 90
per cent sensitivity, 70 per cent specificity). National tuberculosis
prevalence surveys that omit universal sputum microbiological testing might
substantially underestimate the prevalence of asymptomatic tuberculosis in
high-burden countries," Mendelsohn said.
Chest X-Rays
Inadequate for Asymptomatic TB Detection Study
A groundbreaking
study in The Lancet reveals that traditional chest X-rays are failing to detect
a significant portion of tuberculosis cases. Researchers found that over 80% of
infected household contacts showed no symptoms at all. Even more alarming,
standard X-ray screening missed 40% of these asymptomatic infections. This
suggests current screening methods are substantially underestimating TB
prevalence in high-burden countries.
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