Burden of Latent Tuberculosis Infection (LTBI) Among Patients Attending a Tertiary Care Hospital in Eastern India: A...

Latent tuberculosis infection (LTBI) is still neglected and acts as a barrier to the tuberculosis (TB) elimination goal of the National Tuberculosis Elimination Programme (NTEP) by 2025 sustaining TB transmission, particularly in high-burden countries like India. Unlike active TB, which is symptomatic and contagious, LTBI is non-infectious and asymptomatic. However, in LTBI, Mycobacterium tuberculosis (M. tuberculosis) bacilli can reactivate and cause disease under favorable conditions, thus forming a reservoir for future TB cases.  Materials and methods: This hospital-based observational descriptive retrospective study was conducted at a tertiary care center in Eastern India from November 2024 to April 2025. The study included adult patients (>18 years) who were referred for LTBI screening using interferon-gamma release assay (IGRA) during the study period. A total of 236 patients were analyzed. Demographic and clinical details, including age, sex, residence (urban/rural), comorbidities, history of immunosuppressive therapy, documented TB exposure, and other risk factors, were extracted from patient case files and electronic hospital records using a structured data collection format.

LTBI was detected in 56 patients, yielding a prevalence of 23.7% (56/236). Most LTBI-positive individuals were male and aged 30-45 years. A high proportion had underlying autoimmune diseases, while 19.6% (11/56) had no identifiable risk factors which refers to the absence of documented traditional exposures (e.g., household contact), comorbid condition, or clinical indication for screening.

The substantial LTBI burden, particularly among immunocompromised individuals, highlights gaps in targeted screening strategies. Our study identified the proportion of LTBI among patients attending a tertiary care hospital in Eastern India to be 23.7% which is lower than the global average of about 33%. The relatively younger and healthy population participating in the study can also contribute to the low LTBI frequency, as older individuals usually have a high cumulative risk of M. tuberculosis. Although very specific, the use of a single clinical method like IGRA might have led to the sub-detection of LTBI or false-negative results, especially in immunosuppressed individuals. One of the most striking conclusions was the high ratio (71.4%) of LTBI-positive individuals with underlying autoimmune disease. It corresponds to the existing literature, which exposes the increasing sensitivity of this population to TB, especially when one goes through immune stress therapy such as corticosteroids, tumor necrosis factor-alpha (TNF-α) inhibitors, etc.  Conclusion: LTBI represents a silent threat to TB control. Patients with autoimmune disease represent a group at high risk, especially on immunosuppressive medications. A substantial proportion of LTBI-positive individuals had no identifiable risk factors, suggesting that relying solely on known exposure history or symptom-based screening may miss a significant number of infections. Expanded screening using advanced monitoring, modern high-risk diagnosis, and preventive therapy should be an integral part of the national reaction to TB.