- Tuberculosis (TB) is often difficult to diagnose in
children due to the shortage of effective screening methods.
study team found that the test, QuantiFERON-TB assay, which is commonly
used in adults, could effectively predict the risk of developing the
disease among children too.
test is a type of interferon-gamma release assay, which measures the
amount of interferon gamma, a type of cell-signaling protein, released by
certain immune system cells.
simple blood test which is commonly used for screening adults for tuberculosis
could be used
to predict whether children infected with the TB bacteria are likely to
progress to the active disease.
findings are according to a study by a research team at the Stanford University
School of Medicine and five other institutions.
‘Interferon-gamma release assay (IGRA) test can be used to identify children who are at a high risk of developing tuberculosis disease and who would benefit most from investigation and therapy.’
Andrews and his colleagues analyzed medical data from a published trial done by
the South African Tuberculosis Vaccine Initiative between 2009 and 2012.
trial was conducted in a rural area outside Cape Town, where about 30,000 TB
cases are reported every year.
trial involved 2,512 babies who were healthy and HIV-negative, with no known
exposure to the disease.
of the babies in the trial received the experimental vaccine and the other half
received a placebo.
researchers in the trial used the QuantiFERON-TB
, also known as QFT,
to measure infection in the children. They were tested at the start of the
trial and at one year and two years.
test is a type of interferon-gamma release assay, or IGRA, commonly used for TB
screening. After exposing whole blood cells to the TB antigen, the assay
measures the amount of interferon gamma, a type of cell-signaling protein,
released by certain immune system cells.
person is considered negative for the bacteria, if the response measures less
than 0.35 international units per milliliter, and a result higher than that
value is considered to be positive.
Test Results After One Year
the 2,512 children in the study were tested at a year, 172 of them or 6.8%,
were found to be positive carriers of the bacteria, a very high rate of
these, 30 children had already been diagnosed and treated for the active
research team more
closely examined the remaining 142 children who tested positive but had not yet
developed active TB.
found that if children had test results values between 0.35 and 4.0
international units per milliliter, only 2.5% developed the active disease.
among children with values greater than 4.0 international units per milliliter,
around 28% developed active TB.
0.7% of those with a negative test developed TB.
found that as your value goes up, your risk goes up, and the risk really begins
to accelerate after a value of 4," Andrews said. "The children in the high-value
group had a 40-fold higher risk of getting sick, which is a very powerful
high-risk countries like South Africa, where many young children die of the disease
every year and where screening tests for TB in children are ineffective, this
test could be useful.
could be highly valuable in determining which kids will develop TB
disease," said Andrews, an assistant professor of medicine who is the lead
author of the study.
the high rates of TB and the difficulty of diagnosing it in kids, this can be
something that could be done routinely in kids to identify the high-risk
ones," he said. "You could imagine in a high-burden country that at a
child's 12-month visit, they could also get a QuantiFERON test and, if it's
high, they'd get aggressively investigated for TB."
World Health Organization(WHO) does not currently recommend use of this test in
children, but the research team
hope that these new findings will prompt changes in their decision.
we are hoping is that this will show the international community -- the WHO,
CDC and those creating guidelines -- that QuantiFERON testing can be reliable
in kids, and that the quantitative values may be important so we may need to
look a different thresholds than we use in adolescents or adults," Andrews
only drawback of the test is the high cost and the requirement of well-equipped
laboratory and trained personnel to perform. Though the test maybe viable in a
country like South Africa, it may not be of much use in poorer countries.
new findings confirm that the IGRA test for tuberculosis infection performs
differently in young children compared with adults," said Mark Hatherill,
MD, senior author of the study and senior clinical researcher at the South
African Tuberculosis Vaccine Initiative. "More importantly, we now know
that the IGRA test can be
used to identify those children who are at highest risk of developing
tuberculosis disease and who would benefit most from investigation and therapy
study is published online in the Lancet Respiratory
a potentially fatal lung disease caused by Mycobacterium tuberculosis
. It is an airborne disease and is readily transmitted through droplets by
to the WHO, in 2015, TB caused 1.8 million deaths worldwide and is one of the
top 10 killers around the globe.
to infectious disease specialist Jason Andrews, MD, who has been studying the
disease there for a decade, TB is the leading cause of death among adults and
children in South Africa, accounting for some 8.5% of the nation's fatalities.
are commonly screened using sputum testing, and this method does not work in
children, as they typically swallow their sputum after coughing.
can become infected not only through parents but also through contact with
other infected individuals on buses, in churches, schools or other public
is no effective screening tool for children, who are especially vulnerable to
TB and who often show up in clinics at a later stage of the disease, when it is more
difficult to treat. Around 20% of the children are infected by the bacteria developing the
- Introduction to TB - What is TB?, Latent TB & TB disease, symptoms, diagnosis & treatment - (http://www.tbfacts.org/tb/)
- Tuberculosis/ Pulmonary Tuberculosis/ Lung Tuberculosis/ TB - (http://www.medindia.net/patients/patientinfo/tuberculosis.htm)
- Jason Andrews et al. Lancet Respiratory Medicine; (2017)