Important progress made in a cohort study on the onset rate of latent tuberculosis infection in rural areas in China


Led by Research Fellow Lei Gao, a research team of the Institute of Pathogen Biology Tuberculosis Research Center has made important progress in the research on the epidemiology and intervention of latent tuberculosis infection (LTBI) in China. The research findings have recently been published online in Lancet Infectious Diseases, titled "Incidence of active tuberculosis in individuals with latent tuber-culosis infection in rural China: follow-up results of a population-based, multicen-tre, prospective cohort study”.


When people are infected with Mycobacterium tuberculosis, a few of them with low immunity or repeated high-dose infection in a short time will develop signs and symptoms instantly. While some people may clear the infection by their own immune system, most of them will enter a long latent period. About 5%-10% of LTBI will develop into active tuberculosis in a lifetime. Therefore, persistent latent infection in the population is the main source of active tuberculosis. In 2015, the World Health Organization (WHO) announced that the global tuberculosis patients had exceeded AIDS, reaching 10.4 million. Tuberculosis has become one of the world's top ten causes of death. Foreign research shows that a 60-90% reduction in onset rate in high-risk latent infection can be realized through preventive treatment. It is a direct and important mean to reduce the onset rate, as well as an important part of the national tuberculosis prevention and control strategy in Europe and the United States. Considering the signs and symptoms of LTBI, poor protection efficacy of BCG vaccination, and slow reduction in global incidence of tuberculosis (1%-2% annually), WHO issued some guidelines in 2014 to urge more than 130 countries (including China) to carry out LTBI screening and prevention for high-risk population groups. These middle- and high-income countries have a tuberculosis incidence of less than 100 in 10 million. However, China has not yet developed corresponding strategies and national guidelines. It is difficult due to a lack of data on the incidence and characteristics of LBTI, the definition of high-risk population, and intervention studies.


The research project Epidemiological Survey and Cohort Study of Mycobacterium tuberculosis Infection, led by research fellow Lei Gao of the Institute of Pathogen Biology and based on more than 30,000 subjects in five places in China, has previously reported the important epidemiological data and epidemic characteristics of the infection. The findings included the Mycobacterium tuberculosis infection rate in Chinese rural population, the effect of BCG vaccination on the results of LBTI screening, and the annual first-time onset rate of the latent infection group. Recently, the team has also reported the findings of the cohort study on disease onset of LBTI in China. It has found that the annual incidence of active tuberculosis in LBTI populations was 0.87% (0.68% -1.07%). Specifically, the risk of disease onset of men and patients with a history of tuberculosis was 2.36 times and 5.40 times that of women and patients without a history of tuberculosis. Of people with latent infection, about 10% had a history of tuberculosis. If they are targeted for preventive treatment, the onset rate may be reduced by 44%. The team reports for the first time such data as the onset rate of latent tuberculosis infection in China and the influencing factors. It also says that a rapid decline in the onset rate of latent infection can be achieved through latent infection treatment based on patients’ past medical history. The study has laid a solid basis for the team to design and implement further research in this field. It also provides an important reference for China to establish intervention strategies.


The research was funded by the "Twelfth Five-Year" National Infectious Diseases Special Science and Technology Project, and the Chinese Academy of Medical Sciences Medical and Health Science and Technology Innovation Project (2016-I2M-1-013). Other organizations participating in the research include the Chinese Center for Disease Control and Prevention, Jiangsu Provincial Center for Disease Control and Prevention, Gansu Provincial Center for Disease Control and Prevention, Hunan Provincial Tuberculosis Control Center, and Henan Provincial Infectious Disease Hospital. The first author of the article is Research Fellow Lei Gao, et al., and the corresponding author is Research Fellow Qi Jin.



Figure: Onset rate of latent tuberculosis infection in different age groups (QFT+ or TST+) 


                                                 (Institute of Pathogen Biology)