Introduction
Recent research published in Tuberculosis (Edinburgh, Scotland) highlights a critical disparity in the diagnostic accuracy of tuberculosis (TB) infection detection between two QuantiFERON assays, which are shaped by the country of birth’s TB incidence among healthcare workers (HCWs). These findings carry significant implications for TB screening protocols and could contribute to refining guidelines to improve diagnostic accuracy.
Background
Tuberculosis remains a global health threat, with the disease’s burden being highly variable across different regions. In this context, the accurate and early detection of TB infection among healthcare workers is of paramount importance, given their high risk of exposure and potential to transmit the infection to vulnerable populations.
QuantiFERON assays, specifically the QuantiFERON Gold In-Tube (QFT-G) and the new QuantiFERON Gold Plus (QFT+), represent advanced blood tests used for diagnosing TB infection. The QFT+ assay comes with two phlebotomy methods: direct (QFT+D) and single tube transfer (QFT+T).
The Study
The study, led by Saroochi Agarwal and colleagues from the Houston Methodist Research Institute, examined the consistency and results of the QFT-G and QFT+ assays (both QFT+D and QFT+T) among healthcare workers in relation to their countries of birth’s TB incidence rate.
Methodology
Using a single blood draw, researchers compared the QFT-G, QFT+D, and QFT+T assay results from healthcare workers who are annually tested for TB infection. The participants were grouped based on the TB incidence rate of their countries of birth: high (≥150 per 100,000), medium (20-149), and low (<20 TB cases per 100,000).
Findings
The study’s findings revealed notable discordance among assay results. HCWs from countries with medium TB incidence rates had higher positive results for QFT-G (15.6%), QFT+D (16.9%), and QFT+T (22.1%) compared to those from countries with high and low TB incidence rates. Additionally, the level of agreement between the QFT-G and QFT+ (both QFT+D and QFT+T) tests was lower for HCWs from countries with a medium TB incidence rate.
The discrepancies observed raise the issue of whether the QFT+ is potentially more sensitive than the QFT-G among individuals from areas of medium TB incidence. Consequently, this impacts the decision-making process in TB infection management and the potential for over- or under-diagnosis depending on an individual’s country of birth.
Implications
This study’s outcomes underscore the need to factor in epidemiological contexts when interpreting TB diagnostic test results. It may be necessary to adjust screening strategies or to develop new guidelines that account for the variability in test performance based on TB incidence rates in different regions.
Copyright and Acknowledgements
Copyright © 2019 Elsevier Ltd. All rights reserved. The study was a comparative analysis and received research support, not funded by the U.S. government.
References
Agarwal, S., Nguyen, D. T., Lew, J. D., & Graviss, E. A. (2019). Discordance between the QuantiFERON Gold In-Tube and QuantiFERON Gold Plus assays associated with country of birth TB incidence. Tuberculosis (Edinb), 116S, S2–S10. https://doi.org/10.1016/j.tube.2019.04.005
Keywords
1. Tuberculosis diagnosis
2. QuantiFERON assays
3. TB infection screening
4. Healthcare worker TB testing
5. TB incidence impact on tests
Conclusion
The intriguing findings from the research conducted by Agarwal et al. highlight the complexities involved in TB diagnosis, particularly in the context of a globally mobile healthcare workforce. This study calls attention to the need for healthcare systems to acknowledge the heterogeneity in TB incidence worldwide and adapt diagnostics accordingly. The recognition of assay discrepancies based on the country of birth’s incidence rates is vital in the quest to eradicate tuberculosis and safeguard the health of communities and healthcare professionals alike. Further research and discussions are warranted to reconcile these challenges and improve global TB control efforts.