Accurate diagnosis of tuberculosis among children is notoriously difficult because the bacteria causing the disease tend to be detectable in the sputum only of adults, and because the clinical symptoms used to diagnose TB in children are also present in other conditions.
This leads to false positives and consequent inappropriate treatment and increased drug resistance; and to false negatives, which means a correct diagnosis is only possible when it’s too late, after the disease may have spread from the lungs to the brain, or other organs.
In many poor countries, health staff using a standard test fail to detect TB in children up to 93 percent of the time, according to medical charity Médecins Sans Frontières.
According to new research – published in the New England Journal of Medicine - involving 2,800 children hospitalized in South Africa, Malawi and Kenya, the key to better TB diagnosis could lie in 51 genes found in the blood of infected children.
During the seven-year study, researchers determined which of these genes were activated and suppressed among infected children. Using this information to develop a “TB risk score”, the method was found to be accurate in more than 80 percent of cases.
The hope is that the discovery of such a “signature” will lead to a cheap and effective test for childhood TB.
"Childhood TB is a major problem in African hospitals. An accurate test for childhood TB would be an enormous breakthrough, enabling earlier diagnosis, reducing long hospital admissions for investigation of TB suspects, and limiting the number of children treated inappropriately,” Brian Eley from the University of Cape Town, who led the clinical study in South Africa, said.
Joseph Sitienei, head of Kenya’s national TB program, said that while more effective diagnosis would be welcome, the challenge layin ensuring “that they are quickly available in poor countries where they are most needed.”
“Being able to accurately diagnose TB in children means reducing TB related deaths among them,” Sitienei said.
Laura Guay, head of research at Elizabeth Glaser Pediatric Aids Foundation, EGPAF, and a professor at the George Washington University, told IRIN that “additional efforts must be made to ensure that governments, organizations that focus on eradication of TB, and those that fund research in these areas devote sufficient attention and resources to addressing the unique challenges facing the diagnosis and treatment of children with TB.”
Other than hampering treatment, analysts also fear poor diagnosis have led to an underestimation of the burden of the disease among children even in countries where it is endemic. In 2011 for instance, up to 1.3 million deaths in children from TB-endemic countries were attributed to pneumonia yet the cause of the deaths were never verified.
Children who live with TB often live in poor conditions with limited access to healthcare.
Across the world, there are some 16 current or scheduled clinical trials for new drugs to treat TB among children and expectant mothers.
There are also “several research groups that have devoted considerable time and effort to the search for better TB diagnostics for children, including in many research centers throughout Africa,” EGPAF’s Guay, told IRIN.
Better diagnosis is one of the key elements of a roadmap aimed at reaching zero tuberculosis deaths among children drawn up in 2011 by a group of major international health organizations.