Interferon-gamma release assay determined tuberculosis infection: prevalence and risk factors among community-dwelling elderly in Huzhou, a low-endemic region of China

Background Tuberculosis (TB) remains the leading cause of death from a single infectious agent worldwide. This study was conducted in Huzhou City, a low-TB-incidence areas, to investigate the prevalence of tuberculosis infection (TBI) and its associated risk factors among rural elderly population. The findings aim to inform TB elimination strategies in similar low-incidence settings. Methods A cross-sectional study was conducted from May to August 2023 among 1,258 rural residents aged ≥ 65 years in Changxing County, Huzhou City. Data were collected through health examinations, structured questionnaires, and interferon-gamma release assay (IGRA) testing using the QuantiFERON-TB Gold kit (ELISA). Chi-square tests, t-tests, and Fisher’s exact tests were used to compare TBI prevalence across subgroups. Variables with P < 0.05 in univariate analyses were entered into a multivariate logistic regression model. A multi-model strategy was applied to evaluate the association between abnormal imaging findings and TBI. Restricted cubic splines (RCS) were used to examine the dose-response relationship between blood glucose levels and TBI. Results Among the 1,032 enrolled permanent residents aged ≥ 65 years, the IGRA-positive was 9.79% (95% CI: 8.12%–11.75%). Significant differences were observed between IGRA-positive and IGRA-negative individuals in terms of TB history, abnormal chest radiograph findings, sex, immunosuppressive diseases, and smoking status (all P < 0.05). Multivariate analysis identified TB history, abnormal chest radiograph findings, and immunosuppressive diseases as independent risk factors for TBI. Individuals with a prior TB history had 8.49-fold higher odds of TBI (95% CI: 2.01–35.81) versus those without, while abnormal chest radiographs were linked to 1.64-fold higher odds of TBI (95% CI: 1.07–2.50). The multi-model analysis further confirmed that abnormal chest radiograph findings remained a robust predictor of TBI. Additionally, restricted cubic spline analysis revealed a negative dose-response association between blood glucose levels and the risk of TBI. Conclusions In low-incidence areas, individuals with a prior TB history show significantly elevated IGRA positivity. The link between TBI and abnormal chest imaging suggests a practical role for radiography in screening. The inverse association of fasting blood glucose (FBG) with IGRA positivity introduces a new immunologic insight for aging populations that requires further exploration. Collectively, these findings deliver actionable local evidence to inform targeted screening strategies for the elderly.