Incidence and Risk Factors for Tuberculosis Among TBI-Positive Contacts Identified Through Contact Tracing in Catalonia.

OBJECTIVES

To estimate the incidence of tuberculosis (TB) among tuberculin skin test/interferon-γ release assay-positive contacts of patients with pulmonary TB in Catalonia and identify predictors of progression to TB disease.

METHODS

We conducted a cohort study of 1616 tuberculin skin test/interferon-γ release assay-positive contacts of patients with pulmonary TB diagnosed between 2019 and 2021 in Catalonia, Spain. Participants were followed through 2023. Incident TB was defined as disease diagnosed at least 30 days after initiation of treatment in the index case. All cases diagnosed among household contacts younger than 5 years were also considered incident cases. Cox proportional hazards models were used to identify risk factors for incident TB.

RESULTS

During a median follow-up of 3.6 years, 69 contacts (4.3%) developed TB, corresponding to an incidence rate of 1370 cases per 100000 person-years. Children younger than 5 years had the highest risk (adjusted HR [aHR], 25.0; 95%CI, 11-59). An increased risk was also observed among household contacts (aHR, 3.2; 95%CI, 1.6-6.5), smokers (aHR, 2.8; 95%CI, 1.7-4.6), and contacts who did not initiate treatment for TB infection (TBI) (aHR, 7.0; 95%CI, 3.3-14.6). The etiologic fraction of risk was 81.4%. Completion of TBI treatment was strongly protective.

CONCLUSIONS

Prioritizing TBI treatment and adherence among high-risk contacts, especially young children and household contacts, is essential to prevent progression to TB disease.