Systematic reviews have estimated a three-fold increase in active TB in people with diabetes101,102 and risk appears especially high in those with poor glycemic control, insulin dependence and higher Hba1c.103–105
The clinical manifestations of TB are altered by the presence of diabetes. Observational studies suggest people with diabetes are more likely to have cavitary and sputum smear-positive disease but less likely to have extra-pulmonary disease.106–109
Hyperglycemia and poorly controlled diabetes have also been correlated with worse TB treatment outcomes. Multiple retrospective studies observe that people with both TB and diabetes experience delayed sputum culture conversion and higher rates of treatment failure, relapse, mortality and acquisition of rifampin resistance.107,110–114
The prevalence of diabetes in people with newly diagnosed active TB can range up to 25% when routine testing is employed (see Chapter 1: Epidemiology of Tuberculosis in Canada, Figure 11). This has been demonstrated in both high TB-incidence and low TB-incidence countries.115–119 In one Canadian study, diabetes was present in 19.7% of people with active TB.120 Thus, screening for diabetes in patients with active TB is recommended and measurement of glycosylated hemoglobin A1C percentage is commonly used.121–123
Good practice statement
At the time of diagnosis of TB disease, routine screening for diabetes through measurement of glycosylated hemoglobin A1C percentage is suggested and those diagnosed with diabetes should be linked to a diabetes care provider.
Optimization of glycemic control is associated with improved TB treatment outcomes.109,111,124–126 People diagnosed with diabetes during their TB care should receive a referral to a diabetes care provider for long-term management.
Peak serum TB drug concentrations are frequently low in people with diabetes and this may contribute to the poorer TB treatment outcomes seen in this population.3,28,29,33,127 It is not entirely clear how diabetes effects the pharmacokinetics of TB drugs, but increased body weight and gastroparesis with delayed absorption have been suggested as potential factors.127–129 At least one observational study has linked the routine measurement of serum TB drug concentrations in diabetic patients with faster microbiological response to TB treatment.130
Longer treatment duration may be required in people with diabetes. In one large country-wide registry of people under treatment for pulmonary TB in Taiwan, higher relapse rates seen in people with diabetes was mitigated when TB treatment was extended to 9 months total.107 However, the impact of treatment extension was small; of 12,688 people with diabetes and TB, relapse rates were 2.23% in those who received 6 months of treatment and 2.00% in those receiving 9 months (aHR 0.75 (95% CI, 0.59-0.97).
We conditionally recommend that for people with poorly controlled diabetes or evidence of gastroparesis, serum TB drug concentrations be used to optimize drug dosing (poor evidence).
We conditionally recommend treatment extension to 9 months for those with diabetes and cavitary pulmonary or disseminated TB disease (poor evidence).
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