Abstract
Background
Digital Chest X-ray (dCXR) computer-aided detection (CAD) technology uses lung shape and texture analysis to determine the probability of TB. However, many patients with previously treated TB have sequelae, which also distort lung shape and texture. We evaluated the diagnostic performance of two CAD systems for triage of active TB in patients with previously treated TB.
Methods
We conducted a retrospective analysis of data from a cross-sectio nal active TB case finding study. Participants ≥15 years, with ≥1 current TB symptom, and with complete data on history of previous TB, dCXR, and TB microbiological reference (Xpert MTB/RIF) were included. dCXRs were evaluated using CAD4TB (v.7.0) and qXR (v.3.0). We determined the diagnostic accuracy of both systems, overall and stratified by history of TB, using a single threshold for each system that achieved 90% sensitivity and maximized specificity in the overall population.
Results
Of 1,884 participants, 452 (24.0%) had a history of previous TB. The prevalence of microbiologically confirmed TB among those with and without history of previous TB was 12.4% and 16.9% respectively. Using CAD4TB, the sensitivity and specificity was 89.3% (95%CI:78.1-96.0) and 24.0% (95%CI19.9-28.5) and 90.5% (95%CI:86.1-93.3) and 60.3% (95%CI:57.4-63.0) among those with and without previous TB, respectively. Using qXR, the sensitivity and specificity was 94.6% (95%CI:85.1-98.9) and 22. 2% (95%CI:18.2-26.6) and 89.7% (95%CI:85.1-93.2) and 61.8% (95%CI:58.9-64.5) among those with and without previous TB, respectively.
Conclusion
The performance of CAD systems as a TB triage tool is decreased among persons previously treated for TB.
