Background and Objective

Tuberculosis (TB) remains a pressing global health challenge, with millions infected annually. Diagnosing tuberculosis infection (TBI) typically involves measuring interferon-gamma (IFN-γ) release after exposing whole blood to Mycobacterium tuberculosis (Mtb) antigens. Recent insights suggest that hyperglycemia, or elevated blood glucose levels, may influence IFN-γ release. This study explores how glucose intake during an oral glucose tolerance test (OGTT) might impact IFN-γ release and results from IFN-γ-release assays (IGRAs).

Methods

We examined a group of 14 individuals diagnosed with either TB disease or TBI, who participated in two 75-gram OGTTs: one at the beginning and one at the end of their treatment. Blood samples were taken at multiple timepoints before and after glucose ingestion, allowing us to quantify IFN-γ release alongside blood glucose measurements.

Results

Analysis of 24 OGTTs revealed intriguing findings. At the 240-minute mark post-ingestion, IFN-γ release in response to Mtb-specific peptides increased, registering a geometric mean of 3.0 IU/mL, compared to a baseline of 2.5 IU/mL (p = 0.047). A notable leap was also observed in the non-specific mitogen tube, with IFN-γ levels rising from 146.0 IU/mL to 182.6 IU/mL (p = 0.002). Shockingly, changes in plasma glucose did not correlate with IFN-γ release, indicating that glucose intake itself did not alter the IGRAs' effectiveness.

Conclusion

While glucose consumption after a prolonged fast appeared to raise IFN-γ levels after a few hours, the overall impact on IGRA results seems minimal. Therefore, individuals undergoing TB testing need not fret about their glucose levels influencing the accuracy of their results.

The Bigger Picture: TB and Diabetes Correlation

It’s crucial to recognize that diabetes mellitus (DM) is becoming increasingly prevalent, with projections suggesting a rise from 537 million cases in 2021 to a staggering 783 million by 2045. This is particularly concerning as DM significantly raises the risk of TB infections. Studies show that diabetics are 1.5 times more likely to develop TB or TBI, which raises alarms for healthcare systems in low- to middle-income countries already grappling with TB.

Interestingly, the link between TB and DM remains ambiguous. The immune dysfunction associated with DM—compromised macrophage activity and reduced cytokine signaling—may partly explain why patients with diabetes suffer from worse TB outcomes, including treatment failures and higher mortality rates.

Implications for TB Screening

The findings encourage further exploration into the effects of glucose on TB diagnostics. Despite controversial reports on how DM might impact IGRA test results, our study reinforces the notion that glucose intake is unlikely to compromise the accuracy of TB testing using IGRA methods.

Given the ongoing TB epidemic and the looming diabetes crisis, understanding these intricacies could be key in developing more effective screening and treatment protocols. Healthcare professionals can now reassure patients that their sugar intake is not a barrier to accurate TB diagnostics, enabling better management of both chronic illnesses and effective public health responses.

If you or someone you know is at risk, stay informed and consult your healthcare provider about the best practices for TB testing and management!