AUTHOR=Tang Peijun , Liang Ermin , Zhang Xuxia , Feng Yanjun , Song Huafeng , Xu Junchi , Wu Meiying , Pang Yu 

TITLE=Prevalence and Risk Factors of Subclinical Tuberculosis in a Low-Incidence Setting in China

JOURNAL=Frontiers in Microbiology

VOLUME=Volume 12 - 2021

YEAR=2022

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.731532

DOI=10.3389/fmicb.2021.731532

ISSN=1664-302X

ABSTRACT=Objectives: Subclinical tuberculosis (TB) represents a substantial proportion of individuals with TB disease, though limited evidence is available to understand the epidemiological characteristics of these cases. Our aim was to explore the prevalence of subclinical TB patients, and identify the underlying association between the subclinical TB cases in the study setting and Beijing genotype. 
Methods: A retrospective study was conducted among the incident TB patients at the Fifth People’s Hospital of Suzhou between January and December 2018. A total of 380 TB patients were included into our analysis. 
Results: Out of the 380 patients, 81.8% were active TB cases, while the other 18.2% were subclinical TB cases. Compared with patients aged 65 years and over, the risk of having subclinical TB is higher among younger patients. The use of smear, culture and Xpert identified 3, 16, and 13 subclinical TB cases respectively. When using a combination of positive culture and Xpert results, the sensitivity improved to 33.3%. In addition, the neutrophil-to-lymphocyte ratio (NLR) was significantly elevated in the active TB group compared with that in the subclinical TB group. We also observed that the proportion of Beijing genotype in the subclinical TB group was significantly lower than that in the active TB group. 
Conclusions: To conclude, our data demonstrate that approximate one fifth of TB patients were subclinical in Suzhou. MTB could be detected by the existing microbiologic diagnostics in one third of patients with subclinical TB. The patients with subclinical TB are more prone to having low NLR values than those with active TB. Additionally, non-Beijing genotype strains are associated with subclinical TB.