DIABETES mellitus in patients with tuberculosis was not linked to higher household infection and was associated with fewer incident tuberculosis cases over 12 months.
Cohort Study Assesses Household Transmission
Diabetes mellitus increases the risk of tuberculosis progression and is associated with poorer treatment outcomes, raising concern that it could also increase transmissibility. To evaluate this, investigators enrolled 3,109 people with microbiologically confirmed pulmonary tuberculosis between 2009 and 2012, and followed 12,767 household contacts for one year. Household contacts were assessed for tuberculosis infection using a tuberculin skin test and monitored for development of tuberculosis.
Diabetes Mellitus in Patients With Tuberculosis and Transmission Findings
Across infection endpoints, diabetes mellitus in the index patient was not associated with increased household infection. Among child household contacts, diabetes mellitus was not associated with tuberculosis infection, with an adjusted prevalence rate ratio of 1.05 (95% CI: 0.78 to 1.42). Among household contacts who were uninfected at baseline, diabetes mellitus in the index patient was also not associated with incident tuberculosis infection at six months, with an adjusted cumulative rate ratio of 0.85 (95% CI: 0.66 to 1.09).
The pattern differed for incident tuberculosis. Among 12,442 household contacts without tuberculosis at baseline, 368 (3.0%) developed tuberculosis during 12 months of follow up. Household contacts exposed to an index patient with diabetes mellitus had a lower incidence of tuberculosis, with an adjusted cumulative rate ratio of 0.33 (95% CI: 0.13 to 0.85).
Clinical Takeaways for Transmission Dynamics
These findings suggest that diabetes mellitus in patients with tuberculosis does not necessarily translate into higher household transmissibility when measured by tuberculin skin testing, and may be associated with fewer secondary tuberculosis cases over one year. The authors note that this challenges prevailing assumptions that diabetes mellitus uniformly amplifies transmission because of its association with smear positivity and cavitary disease, indicating a more complex relationship between diabetes mellitus and tuberculosis transmission dynamics.
Reference: Huang CC et al. Impact of Diabetes Mellitus in TB Patients on TB Transmission. Clin Infect Dis. 2025; doi:10.1093/cid/ciaf647.
