The Effect of HIV on the Association of Hyperglycaemia and Active Tuberculosis in Zambia, a Case-Control Study.

Objectives: To determine if HIV modifies the association between hyperglycaemia and active tuberculosis in Lusaka, Zambia.

Methods: A case-control study among newly-diagnosed adult tuberculosis cases and population controls in three areas of Lusaka. Hyperglycaemia is determined by random blood glucose (RBG) concentration measured at the time of recruitment; active tuberculosis disease by clinical diagnosis, and HIV status by serological result. Multivariable logistic regression is used to explore the primary association and effect modification by HIV.

Results: The prevalence of RBG concentration ≥ 11.1 mmol/L among 3843 tuberculosis cases was 1.4% and among 6977 controls was 1.5%. Overall, the adjusted odds ratio of active tuberculosis was 1.60 (95% CI 0.91-2.82) comparing those with RBG concentration ≥ 11.1- < 11.1 mmol/L. The corresponding adjusted odds ratio among those with and without HIV was 5.47 (95% CI 1.29-23.21) and 1.17 (95% CI 0.61-2.27) respectively; p-value for effect modification by HIV = 0.042. On subgroup analysis, the adjusted odds ratio of smear/Xpert-positive tuberculosis was 2.97 (95% CI 1.49-5.90) comparing RBG concentration ≥ 11.1- < 11.1 mmol/L.

Conclusions: Overall, no evidence of association between hyperglycaemia and active tuberculosis was found, though among those with HIV and/or smear/Xpert-positive tuberculosis there was evidence of association. Differentiation of hyperglycaemia caused by diabetes mellitus and stress-induced hyperglycaemia secondary to tuberculosis infection is important for a better understanding of these findings.