Background
Diabetes mellitus (DM) increases tuberculosis (TB) risk. We assessed the prevalence of hyperglycaemia (DM and impaired glucose regulation (IGR)) in TB patients and the association between hyperglycaemia and TB at enrolment and 3 months after TB treatment in the context of HIV-infection.

Methods
Adults presenting at a Cape Town TB clinic were enrolled. TB cases were defined by South African guidelines, while non-TB participants were those who presented with respiratory symptoms, negative TB tests and resolution of symptoms 3 months later without TB treatment. HIV status was ascertained through medical records or HIV-testing. All participants were screened for DM using HbA1c and fasting plasma glucose at TB treatment and after 3 months. The association between TB and DM was assessed.

Results
Overall DM prevalence was 11.9% (95% CI: 9.1–15.4) at enrolment and 9.3% (95% CI: 6.4–13) at follow-up; IGR prevalence was 46.9% (95% CI 42.2–51.8) and 21.5% (95% CI 16.9–26.3) at enrolment and follow-up. TB/DM association was significant at enrolment (OR 2.41 (95% CI 1.3–4.3)) and follow-up (OR 3.3 (95% CI 1.5–7.3)), whilst TB/IGR association was only positive at enrolment OR 2.3 (95% CI 1.6–3.3). The TB/DM association was significant at enrolment in both new and pre-existing DM, but only persisted at follow-up in HIV-1-infected pre-existing DM.

Conclusion
Our study demonstrated high prevalence of transient hyperglycaemia and a significant TB/DM and TB/IGR association at enrolment in newly diagnosed DM, but persistent hyperglycaemia and TB/DM association in HIV-1-infected pre-existing DM, despite TB therapy.