The Influence of Diabetes, Glycemic Control, and Diabetes-Related Comorbidities on Pulmonary Tuberculosis

BACKGROUND: To assess the influence of diabetes mellitus (DM), glycemic control, and diabetes-related comorbidities on manifestations and outcome of treatment of pulmonary tuberculosis (TB). METHODOLOGY/PRINCIPAL FINDINGS: Culture positive pulmonary TB patients notified to health authorities in three hospitals in Taiwan from 2005–2010 were investigated. Glycemic control was assessed by glycated haemoglobin A1C (HbA1C) and diabetic patients were categorized into 3 groups: HbA1C<7%, HbA1C 7–9%, HbA1C>9%. 1,473 (705 with DM and 768 without DM) patients were enrolled. Of the 705 diabetic patients, 82 (11.6%) had pretreatment HbA1C<7%, 152 (21.6%) 7%–9%, 276 (39.2%) >9%, and 195 (27.7%) had no information of HbA1C. The proportions of patients with any symptom, cough, hemoptysis, tiredness and weight loss were all highest in diabetic patients with HbA1C>9%. In multivariate analysis adjusted for age, sex, smoking, and drug resistance, diabetic patients with HbA1C>9% (adjOR 3.55, 95% CI 2.40–5.25) and HbA1C 7–9% (adjOR 1.62, 95% CI 1.07–2.44) were significantly more likely to be smear positive as compared with non-diabetic patients, but not those with HbA1C<7% (adjOR 1.16, 95% CI 0.70–1.92). The influence of DM on outcome of TB treatment was not proportionately related to HbA1C, but mainly mediated through diabetes-related comorbidities. Patients with diabetes-related comorbidities had an increased risk of unfavorable outcome (adjOR 3.38, 95% CI 2.19–5.22, p<0.001) and one year mortality (adjOR 2.80, 95% CI 1.89–4.16). However, diabetes was not associated with amplification of resistance to isoniazid (p = 0.363) or to rifampicin (p = 0.344). CONCLUSIONS/SIGNIFICANCE: Poor glycemic control is associated with poor TB treatment outcome and improved glycemic control may reduce the influence of diabetes on TB.