Using QAngio XA® 3D/QFR® to measure quantitative flow ratio may be an alternative to performing standard invasive coronary angiography alone, according to a study published in Health Technology Assessment.

For the systematic review, researchers used 39 studies evaluating QAngio XA 3D/QFR (n=5440 participants) and 3 studies evaluating CAAS® vFFR® (n=500 participants). Studies of QAngio XA 3D/QFR included results on clinical effectiveness, diagnostic accuracy, economic data, and implementation. Several databases were searched to find studies on either QAngio XA 3D/QFR or CAAS vFFR, which included a comparison with fractional flow reserve among those with intermediate stenosis.

Quality assessment of diagnostic accuracy was performed to assess bias risk, and diagnostic accuracy was assessed using meta-analysis. The clinical impact of using QAngio XA 3D/QFR was assessed using a simulation study, and a de novo decision-analytic model was used to evaluate how cost effective both technologies were compared with either invasive coronary angiography or invasive fractional flow reserve alone. To assess the stability of results under different data sources and assumptions, the study researchers performed scenario analyses.

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QAngio XA 3D/QFR quantitative flow ratio performed favorably in predicting significant fractional flow reserve with a cutoff point of less than or equal to 0.80. For contrast-flow quantitative flow ratio, sensitivity was 85% (95% CI, 78-90), and specificity was 91% (95% CI, 85-95). The majority (95%) of quantitative flow ratio measurements fell within 0.14 of fractional flow reserve, with 50% within 0.04. A full meta-analysis of CAAS vFFR diagnostic accuracy was not possible due to limited data on implementation and clinical outcomes.

Researchers indicated that the use of quantitative flow ratio instead of fractional flow reserve led to a slight increase (40.2% to 42.0%) in quantity of revascularizations, as well as a potential small rise in the number of adverse cardiac events (an additional 1/1000 participants). Invasive coronary angiography with confirmatory fractional flow reserve appeared to have the highest net cost-effectiveness, followed by QAngio XA 3D/QFR and CAAS vFFR without fractional flow reserve. There was a small difference in net benefit between the first- and second-best strategies: 0.007-0.012 quality-adjusted life-years per participant.

Limitations to this study include heterogeneous results for studies dealing with CAAS vFFR technology, insufficient data to investigate clinical characteristics, limited data on impact or implementation of QAngio XA 3D/QFR, and limited data available to estimate vFFR diagnostic accuracy.

With respect to making revascularization decisions, the study authors concluded that “using QFR as measured with QAngio XA 3D/QFR is preferable to making decisions based on DS assessment using standard [invasive coronary angiography] alone.” The study authors also noted evidence for “small differences in net [economic] benefit.”


Duarte A, Llewellyn A, Walker R, et al. Non-invasive imaging software to assess the functional significance of coronary stenoses: a systematic review and economic evaluation. Health Technol Assess. 2021;25(56):1-230. doi: 10.3310/hta25560