Diagnosis of pediatric pulmonary TB: molecular genetic assays. More information from Nina Zherebko, consultant of the USAID Support TB Control Efforts in Ukraine Project
Challenges in diagnosing pediatric TB
In Ukraine, pediatric TB is underdetected. According to the WHO experts, TB cases among children should be approximately 5-10% of TB cases in the adult population as children get the infection from adults. Therefore, laboratory diagnosis of pulmonary TB in children is an important component of diagnosing the disease, which has symptoms similar to other respiratory diseases.
Diagnosing pediatric TB is challenging as TB in children is often paucibacillary. It means that the amount of the pathogen in the laboratory samples is low. Young children are not able to produce enough sputum for running an assay, so there may be a need to use sputum induction, aspiration of stomach contents or nasopharyngeal lavages, which may cause discomfort, pain and distress in children.
Implementing the molecular genetic method of diagnosing pediatric TB
Starting from November 2021, 12 regions of Ukraine started implementing diagnosis of pulmonary TB in children using stool samples with GeneXpert machines and Xpert MBT/Rif Ultra cartridges as part of the USAID Support TB Control Efforts in Ukraine Project.
The benefit of this method is that stool samples can be easily obtained and contain Mycobacterium tuberculosis from the sputum swallowed by the child.
When implementing the pilot project, there were some cases when the TB pathogen was not detected in other materials tested, but stool samples helped to establish the correct diagnosis. Since June 2022, this method of pediatric TB diagnosis is available in all regions of Ukraine.
Work in the times of war
In spite of the war, the molecular genetic method of TB diagnosis is implemented even in the occupied territories. Thus, in Kherson region, laboratory officers were only able to perform an assay of a child’s feces due to their limited resources. The assay confirmed TB, and the little patient was prescribed with timely treatment.
Feces are a complex material for molecular diagnostics, requiring additional sample preparation. However, modern diagnostic methods and Xpert cartridges allow to test stool samples for the resistance to 1st and 2nd line drugs just in one day, while it takes up to 1.5 months with bacteria culture method.
Thus, in one of the Project implementation regions after a positive result was received using the Xpert MBT/Rif Ultra cartridge, on the same day the sample was tested using the Xpert XDR cartridge to get data on the sensitivity of the pathogen to second-line TB drugs. With such assay results, the doctor could receive this crucial information much quicker to prescribe correct and effective therapy to the patient.