More emphasis necessary for TB prevention in paediatric population
A documented household exposure should trigger prompt contact tracing to allow timely diagnosis and to prevent the development of tuberculosis (TB) disease, according to a specialist.
The treatment of latent TB infection (LTBI) in children is fairly safe and effective. Adverse events are relatively uncommon; the most common side effects include nausea and vomiting, said infectious diseases and paediatric consultant Dr. Tan Kah Kee, who was speaking at the Malaysian Thoracic Society (MTS) Annual Congress 2017, held in Kuala Lumpur recently. It is important to educate caregivers to monitor these symptoms, and to assess the child’s clinical symptoms and growth during follow-up, he added.
Traditionally, TB is divided into two distinct states: LTBI and disease. LTBI is the state where the patient is asymptomatic and Mycobacterium tuberculosis is dormant. A tuberculin skin test (TST) will produce a positive result while physical examination and chest X-ray will be normal, said Tan. Management of a patient with an infection will include either an isoniazid monotherapy for 6 months or isoniazid plus rifampicin for 3 months. Conversely, in the TB disease state, the patient is symptomatic and M. tuberculosis is actively replicating. Similar to the infection state, TST will have a positive result but unlike the infection state, physical examination and chest X-ray will be abnormal in the disease state. Management will require a multiple drug regime, said Tan.
Nevertheless, current TB concept states that both LTBI and the TB disease states may not be the only two states, and that there is a spectrum of immunological responses to a TB infection. The spectrum includes infection elimination by innate immunity, acquired immune response, early disease with minimal symptoms and advanced clinical TB, Tan explained.
TSTis the preferred investigation test for TB in children. It assesses the degree of hypersensitivity to tuberculin purified protein derivative and the reaction size correlates with the future risk of developing TB disease. If the reaction is bigger than 15 mm, it is unlikely to be due to previous BCG vaccination or exposure to environmental mycobacteria, he explained. More than half of infants who were given BCG at birth will have a non-reactive TST at 9 to 12 months of age. However, a negative TST does not exclude the diagnosis of TB as severe malnutrition, HIV infection, disseminated TB and immunosuppressive drugs can cause false negative results.
It is estimated that as many as one-third of people worldwide have LTBI. The lifetime risk of reactivation for LTBI is around five to 10 percent. Unfortunately, most develop TB disease within the first 5 years after initial infection and the risk increases significantly if the patient has predisposing factors. [WHO. Available at: http://www.who.int/tb/challenges/ltbi/en/. Accessed on 28 July]