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

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

doi:10.3389/fmicb.2021.731532

Abstract

Objectives: Subclinical tuberculosis (TB) represents a substantial proportion of individuals with TB disease, although limited evidence is available to understand the epidemiological characteristics of these cases. We aimed to explore the prevalence of subclinical patients with TB and identify the underlying association between the subclinical TB cases in the study setting and the Beijing genotype.Methods: A retrospective study was conducted among patients with incident TB at the Fifth People’s Hospital of Suzhou between January and December 2018. A total of 380 patients with TB were included in our analysis.Results: Of the 380 patients, 81.8% were active TB cases, whereas the other 18.2% were subclinical TB cases. Compared with patients aged 65 years and older, 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 was significantly elevated in the active TB group compared with that in the subclinical TB group. We also observed that the proportion of the Beijing genotype in the subclinical TB group was significantly lower than that in the active TB group.Conclusion: To conclude, our data demonstrate that approximately one-fifth of patients with TB were subclinical in Suzhou. Mycobacterium tuberculosis 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 neutrophil-to-lymphocyte ratio values than those with active TB. Additionally, non-Beijing genotype strains are associated with subclinical TB.

Highlights

Tuberculosis (TB), caused by the Mycobacterium tuberculosis (MTB) complex, is the leading infectious cause of mortality worldwide (Glaziou et al, 2018; World Health Organization, 2020)
Considering that the clinical symptoms correlate with the increasing bacillary burden and subsequent host damage (Lenaerts et al, 2015), the preceding asymptomatic periods can be defined between latent infection and active TB disease, including incipient and subclinical TB (Drain et al, 2018)
We aimed to explore the prevalence of subclinical patients with TB and identify the underlying association between the subclinical TB cases in Suzhou and Beijing genotypes

Summary

Introduction

Tuberculosis (TB), caused by the Mycobacterium tuberculosis (MTB) complex, is the leading infectious cause of mortality worldwide (Glaziou et al, 2018; World Health Organization, 2020). Reducing the morbidity and mortality of TB requires a comprehensive understanding of its clinical pathogenic spectrum from infection to disease onset (Lenaerts et al, 2015; Drain et al, 2018). Considering that the clinical symptoms correlate with the increasing bacillary burden and subsequent host damage (Lenaerts et al, 2015), the preceding asymptomatic periods can be defined between latent infection and active TB disease, including incipient and subclinical TB (Drain et al, 2018). The World Health Organization’s (WHO’s) End TB Strategy cannot be achieved without enhanced efforts to hinder the transmission spread by the millions of people who have subclinical TB (Kendall et al, 2021)

Objectives

Methods

Results

Discussion

Conclusion