Abstract
BACKGROUND: Indonesia reported the second-highest global burden of tuberculosis after India, with a 2.6% increase in cases from the previous year. OBJECTIVE: This study aimed to evaluate case-finding of latent tuberculosis infection (LTBI) and differences in tuberculin induration diameters among household contacts of index patients, stratified by contact follow-up interval (1-180 months). Methods: A total of 240 index patients were recruited from four primary health cares in Simalungun District and assigned to four time interval groups in duration of 0-180 months. Tuberculin skin tests were administered to 912 contacts. Latent tuberculosis infection incidence was analyzed using proportion tests, and differences in induration diameter across time interval were tested using ANOVA (α = 0.05). RESULTS: The overall latent tuberculosis infection incidence was 22.4% (95% CI: 19.2-26.1) across time intervals of 1-180 months, with rates of 10.7% for 1-6 months, 21.4% for 7-24 months, 30.2% for 25-60 months, and 28.0% for 61-180 months. Significant differences in induration diameter were observed between 1-6 months and 7-24 months (p < 0.01), 1-6 months and 25-60 months (p < 0.01), and 1-6 months and 61-180 months (p < 0.01). CONCLUSION: Increasing incidence of latent tuberculosis infection across time intervals of 0-180 months, indicating a rising potential for future active tuberculosis cases. This pattern reflects a progressive tuberculin conversion among household contacts, particularly between 0-6 and 7-24 months.