Impact of cigarette smoking on latent tuberculosis infection: does age matter?

Abstract

To the Editor: Latent tuberculosis infection (LTBI) is defined by evidence of immunological responses by Mycobacterium tuberculosis proteins in the absence of clinical symptoms/signs of active diseases [1]. People who have increased likelihood of tuberculosis (TB) exposure and those with clinical conditions that increased their risk of progressing from LTBI to TB disease are regarded as high-risk groups for developing TB disease and should be considered for LTBI testing and treatment. Both tuberculin skin test (TST) and T-cell based interferon-γ release assays (IGRAs) are available diagnostic tool for LTBI, but IGRAs avoid the interferences from bacille Calmette–Guerin (BCG) vaccination and non-tuberculous mycobacterium (NTM). Cigarette smoke has adverse effects in respiratory immune function and is widely reported to be associated with an increased risk of respiratory a tract infection, including TB [2, 3]. However, only a few studies investigated the impact of smoking on LTBI, and none of these studies used IGRAs to diagnose LTBI [4, 5]. The European Respiratory Journal recently published a perspective review focused on the role of diagnosis and treatment of LTBI to improve TB control and eventually TB elimination [6]. To eliminate TB on a global scale the identification and sterilisation of latently infected individuals, especially those in high-risk groups, is of paramount importance. Concerning the close correlation between cigarette smoking and active TB, the association between LTBI and smoking deserves further clarification with IGRAs as a diagnostic tool. To elucidate the issue, we enrolled inpatients and outpatients who were considered at risk for LTBI and …