Epidemiology of latent tuberculosis infection among patients with and without diabetes mellitus

Background: Individuals with type 2 diabetes mellitus (DM) are at a greater risk of tuberculosis (TB) reactivation. There is a paucity of information about the risk factors associated with latent tuberculosis infection (LTBI) in patients with diabetes.

Objective: We conducted an observational study to compare the prevalence and risk factors associated with LTBI factors in Malaysian adults with and without DM.

Methods: Four hundred and four patients with DM and 359 patients with non-DM at a regional primary care clinic were recruited as participants in this case-control study. The tuberculin sensitivity test (TST) was performed. The presence of LTBI was defined by a TST value of 10 mm in DM patients and 10 mm in the non-DM group. A logistic regression model was used to identify variables associated with LTBI.

Results: There was no statistical significant difference in the prevalence rates seen between the DM and non-DM group of the study. LTBI prevalence among patients with DM was 28.5%. The proportion of patients in the non-DM group with LTBI was 29.2%. When a critical cut-off of 8 mm was used, the adjusted odds ratio of LTBI in DM patients was 1.88 (95% confidence interval: 1.22-2.82). Smoking was an independent risk factor for LTBI regardless of DM status. HbA1c levels or anthropometric measurements were not associated with LTBI in diabetic patients.

Conclusions: There is no significant risk of contracting LTBI in DM patients using the standard 10-mm TST cut-off. Nonetheless, using lower cut-offs in a DM population appear valid. Smoking is an important predictor of LTBI.