Incidence of Tuberculosis Infection and Disease in Household Contacts of Multidrug-Resistant Pulmonary Tuberculosis Patients

Background Household contacts (HHCs) of MDR-TB patients are at increased risk of developing TB infection (TBI) as well as TB disease. Early identification of TBI is crucial for prevention of TB disease, however Indian data on MDR-TB contacts is limited. Methods We conducted a prospective cohort study (February 2022 to September 2024) in a tertiary care centre enrolling patients from urban slum neighborhoods of New Delhi. 147 HHCs of 36 MDR-TB cases were enrolled for the study and underwent a tuberculin skin test (TST). TBI was defined as TST ≥ 10 mm. Contacts were followed for 2 years for incidence of TB disease. Information on potential risk factors and other co-morbidities such as body mass index, smoking, alcohol consumption, diabetes, hypertension and household overcrowding were recorded. Results TST positivity was seen in 24.48% (36/147) HHCs. During follow-up of 2 years, 5 of 36 TST-positive HHCs (16.67%) developed TB as compared to 1 of 91 TST-negative (1.1%) HHCs. The relative risk of developing TB was 12.75 times higher for TST-positive versus TST-negative HHCs. TB incidence was significantly higher in overcrowded households and among younger or underweight HHCs. Conclusions Our study reinforces the high risk of transmission of MDR-TB to household contacts. Potential risk factors for TB infection include younger, malnourished HHCs with low BMI and household overcrowding. These findings underscore an urgent need to strengthen contact screening and implement targeted interventions in order to curb transmission of tuberculosis amongst contacts.