Glycemic Control and the Prevalence of Tuberculosis Infection: A Population-based Observational Study

Background. Several cohort studies demonstrate that diabetics are at increased risk for active tuberculosis, and poor glycemic control may exacerbate this risk. A higher prevalence of tuberculosis infection at baseline among diabetics may partially explain these results; however, no population-based studies have investigated this association. Furthermore, whether glycemic control modifies the relationship between diabetes and tuberculosis infection, as it does with active tuberculosis, is unknown. Methods. Diabetics were diagnosed through physician evaluation and using 3 laboratory tests including hemoglobin A(1C) (HbA(1C)), fasting plasma glucose (FPG), or 2-hour plasma glucose (PG). Tuberculosis infection was diagnosed through tuberculin skin tests, and glycemic control was assessed linearly and categorically using recommended targets. Results. Among 4215 participants, the prevalence of tuberculosis infection was 4.1%, 5.5%, and 7.6% in nondiabetic, prediabetic, and diabetic participants (P trend = .012). In multivariate analysis, diabetes was associated with tuberculosis infection (adjusted odds ratio [AOR], 1.5; 95% confidence interval [CI], 1.0-2.2). Compared to nondiabetics, diabetics who were undiagnosed (AOR, 2.2 and 1.2 in diagnosed diabetics), FPG >130 mg/dL (AOR, 2.6 and 1.3 in diabetics with FPG <= 130 mg/dL), or not on insulin (AOR, 1.7 and 0.8 in diabetics on insulin) had elevated tuberculosis infection rates. In a linear dose-response analysis, increasing values of FPG (AOR, 1.02 per 1-mg/dL; 95% CI, 1.01-1.03), PG (AOR, 1.02 per 1-mg/dL; 95% CI, 1.01-1.04), and HbA(1C) (AOR, 1.13 per 1%; 95% CI, 1.04-1.22) all predicted tuberculosis infection. Conclusions. Our results suggest glycemic control may modify the relationship between tuberculosis infection and diabetes.