Preventative treatment is recommended for everyone who tests positive for tuberculosis.

Preventative treatment for tuberculosis (TB) can prevent latent TB infections from developing into a fatal disease. Although TB infection is completely curable, there is no global consensus on which subgroups of people exposed to TB should be prioritized for preventive treatment, and whether the benefits of this treatment vary depending on factors such as age or confirmed infection. p>

A new study led by a researcher at Boston University School of Public Health (BUSPH) clarifies this issue, showing that people with confirmed TB infection—that is, a positive skin or blood test—should receive priority treatment in low-prevalence settings, regardless of their age.

However, in high-burden settings, all exposed individuals should be considered for preventive treatment, even without confirmed infection, according to results published in The Lancet Respiratory Medicine. P>

This strategy could help end the TB epidemic and support global efforts to reduce TB deaths by 95% by 2035 (compared to 2015 estimates). In 2022, there were more than 10 million cases of active TB worldwide, resulting in 1.5 million deaths.

"Tuberculosis affects tens of millions of people each year and has long-term consequences, even after recovery,” said study lead and corresponding author Dr. Leonardo Martinez, assistant professor of epidemiology at BUSPH. “Finding ways to optimize prevention is really important to combat the epidemic.”

For the study, Dr. Martinez and colleagues conducted a comprehensive review and analysis to identify new cases of TB among people who were in close contact with diagnosed cases, and compared the effectiveness of preventive treatment in these exposed individuals according to age, infection status and TB load in their conditions.

Among 439,644 participants, the team found that TB preventive treatment was 49% effective among the 2,496 people who developed TB, but especially among those with a positive skin or blood test (for whom the effectiveness was 80%).

Remarkably, the researchers found that TB preventive treatment was not effective for most people who showed no signs of infection, except for children under 5 years of age.

For those who had a positive skin or blood test, treatment effectiveness was comparable across all age groups - adults, children aged 5-17 years and children

The team also estimated the number of people who would need to receive treatment (NNT) to prevent one person from developing TB. Regardless of infection status, NNT was lower in high-burden conditions (29 to 43 people) compared with low-burden conditions (213 to 455 people). Although individuals with negative blood or skin tests do not appear to benefit from preventive treatment, the researchers argue that the overall low NNT may justify prioritizing treatment of all exposed contacts in areas where testing for TB infection is not available.

"While it is critical to find and treat people who are spreading TB in the community, the threat of global TB will never end until people with latent TB are treated," said study co-author Dr. S. Robert Horsburgh, professor of global health. "The results of this study show how effective this treatment can be."