Tuberculosis and diabetes: increased hospitalisations and mortality associated with renal impairment

Background Diabetes mellitus (DM) triples a person's risk of active tuberculosis (TB) and is associated with increased mortality. It is unclear whether diabetes status and/or the associated renal dysfunction is associated with poor TB outcomes in New Zealand, which has high diabetes screening. Aim To characterise the population of TB-DM and TB-alone to assess the effect of diabetes status and renal function on hospitalisation and mortality. Methods Clinical records from all adult patients diagnosed with TB in Auckland over a 6-year period (2010–2015) were reviewed. Baseline demographics, clinical presentation and microbiological data were assessed to compare the rates of hospitalisation and mortality between those with TB-DM and TB-alone. Statistical significance was defined as P < 0.05. Results A total of 701 patients was identified with TB; 120 (17%) had an unknown diabetes status and were excluded, and 135 had co-existing diabetes. The TB-DM and TB-alone groups had similar distribution of TB site and proportions of Mycobacterium tuberculosis culture positivity. Univariate analysis showed TB-DM patients had statistically significantly higher proportions of acute hospitalisation and mortality. Multivariate logistic regression showed only a reduced estimated glomerular filtration rate (eGFR) accounted for the higher rates of hospitalisation, with the odds of hospitalisation increasing by 2% for every unit decrease in eGFR. The odds of mortality increased by 6% for every year increase in age, and the odds of mortality increased by 3% for every unit reduction in eGFR. Conclusions Diabetes is associated with higher TB hospitalisation and mortality; however, this is likely mediated by increased age and chronic kidney disease.