Tackling latent tuberculosis with preventive therapy
Published: 29 Mar 2018
Tuberculosis (TB) is an airborne disease that commonly affects the lungs and also other body parts such as the brain, lymph nodes, kidneys and bones. It is usually curable with medication taken over a period of six to nine months.
Most people are not infected upon exposure to TB bacteria, instead developing a latent form of TB which is not infectious. However, as they age and their immunity weakens, latent TB can potentially turn into infectious active TB. The symptoms include a persistent cough, fever and chest pain.
This is a growing concern in Singapore, as up to 30 per cent of older residents have latent TB. This is due to its prevalence in Singapore until the 1970s, according to the Ministry of Health (MOH).
In response, the National University Hospital (NUH) has introduced routine latent TB screenings in recent years for patients with weakened immune systems, such as those undergoing liver and bone marrow transplants, and those who are about to take medication for different types of arthritis, like rheumatoid arthritis. These screenings were also extended to patients with the human immunodeficiency virus (HIV) in August 2017, following a hospital study which revealed that TB could have been prevented in up to 40 per cent of these cases by sending them for preventive screening.
“Preventive therapy for latent TB would significantly decrease the progression to active TB, which can be fatal as it infects the brain, causing strokes and significant morbidity,” according to Assistant Professor Catherine Ong, an infectious diseases specialist with NUS Medicine. “In addition, only one medicine, compared to four, is taken without the need for directly observed therapy (for latent TB). This translates to lower costs, and less chance of drug adverse events,” she added.
Currently, approximately 20% of the 300 HIV patients at NUH have been screened when previously none had undergone the preventive screening, said Asst Prof Ong. Blood tests to check for latent TB normally cost $255, but Singaporean patients only pay a fee of $100 as the costs are subsidised.
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