The impact of an oral glucose load on IFN-[gamma]-release in persons infected with Mycobacterium tuberculosis

To diagnose tuberculosis infection (TBI), whole blood is incubated with M.tuberculosis (Mtb)-specific peptides and the release of interferon-[gamma] (IFN-[gamma]) is measured in IFN-[gamma]-release assays (IGRAs). Hyperglycaemia and fluctuations in blood glucose may modulate IFN-[gamma]-release. Here, we investigated if glucose intake affects IFN-[gamma]-release or IGRA results in IGRAs taken during an oral glucose tolerance test (OGTT). Persons with TB disease (TB) or TBI underwent a standard 75-g OGTT at the start and end of treatment for TB or TBI. Blood for the IGRA QuantiFERON-TB Gold Plus (QFT) containing Mtb-specific tubes (TB1 and TB2), a non-specific mitogen tube (MIT) and an empty control tube (NIL) was drawn at sample-timepoints -15 (baseline), 60, 90, 120 and 240 min during the OGTT. Blood glucose was measured in parallel at all timepoints. IFN-[gamma]-release (after subtraction of NIL) at each timepoint was compared with baseline using linear-mixed-model analysis. Twenty-four OGTTs from 14 participants were included in the final analysis. Compared to baseline, IFN-[gamma]-release was increased at sample-timepoint 240 min for TB1; geometric mean (95% confidence interval) 3.0 (1.5-6.2) vs 2.5 (1.4-4.4) IU/mL (p = 0.047), and MIT; 182.6 (103.3-322.9) vs 146.0 (84.0-254.1) IU/mL (p = 0.002). Plasma glucose levels were not associated with IFN-[gamma]-release and the QFT test results were unaffected by the OGTT. Ingestion of glucose after a 10-h fast was associated with increased IFN-[gamma]-release after 240 min in the MIT tube. However, there was no association between plasma glucose levels at the QFT sampling timepoint and IFN-[gamma]-release. Furthermore, the QFT test results were not affected by glucose intake. The overall effect of an OGTT and prevailing plasma glucose levels on IFN-[gamma]-release in IGRAs seem limited.