Abstract:

Objective To determine the prevalence and identify the risk factors of latent tuberculosis infection （LTBI） among close contacts of active pulmonary tuberculosis， and to evaluate the diagnostic performance of the domestic AIMTB fluorescent immunochromatographic reagent in detecting LTBI within this population. Methods A prospective study design was employed to continuously recruit 267 adult family close contacts of patients with active pulmonary tuberculosis in the tuberculosis department from January to October 2024. After enrollment， eleven cases were excluded because of age mismatch or the inability to provide compliant testing samples， leaving 256 eligible subjects for the study. General demographic information and clinical data were gathered， and chi-square tests and association strength analyses were carried out. Blood samples were examined for AIMTB and QFT-Plus by trained laboratory personnel， and data analysis was carried out. Results In this study， a total of 97 males and 159 females participated， with an average age of （48.47 ± 14.96） years. The LTBI detection rate was significantly higher among individuals with middle school education or below compared to those with high-school education or above. Moreover， the detection rate was significantly higher in smokers than in non-smokers and in drinkers than in non-drinkers. The results of multivariate logistic regression indicated that age ≥ 60 years （OR = 1.800， 95%CI： 1.00-3.241） and smoking （OR = 3.182， 95%CI： 1.676-6.041） are independent risk factors for LTBI. The positive rate of the QFT-Plus test was 33.6%（86/256）， and that of the AIMTB test was 38.3%（98/256）. The positive agreement rate between the two testing methods reached 93.68%， the negative agreement rate was 93.02%， and the overall agreement rate was 90.63%. The consistency strength evaluated by Cohen's Kappa coefficient was 0.797， suggesting high diagnostic consistency between the two testing methods. A further subgroup analysis of the groups with significant differences in detection rates revealed that both methods showed high consistency across different genders， age stratifications， and education levels， with kappa values greater than 0.75， except for the age group ≥ 60 years（0.740）. Under ROC curve analysis， the area under the curve was 0.989. Conclusions In populations with close contact， smoking serves as a risk factor for LTBI， and a certain proportion of LTBI cases in this population can be ascribed to smoking. The AIMTB and QFT-Plus tests demonstrate a high level of consistency in LTBI screening among close contacts， featuring high sensitivity and specificity. Moreover， the AIMTB test holds specific clinical value and public health significance in the screening of LTBI.

Key words: latent tuberculosis infection, gamma interferon release assay, close contacts, diagnostic consistency