Findings from the FAVOR II study in China, as well as in Europe and Japan, demonstrate the clinical utility of quantitative flow ratio (QFR) for use in diagnostic catheterization laboratories, said researchers presenting at Transcatheter Cardiovascular Therapeutics (TCT 2017) meeting. Additionally, QFR has the potential to improve angiography-based identification of functionally-significant stenosis during coronary angiography.

The FAVOR II China study, also published in the Journal of the American College of Cardiology, enrolled 308 patients from five centers in China between June and July 2017 and assessed the diagnostic performance of QFR (QFR) for diagnosis of hemodynamically-significant coronary stenosis defined by fractional flow reserve (FFR) <= 0.80. All patients had at least one lesion with diameter stenosis of 30% to 90% and reference diameter >= 2mm by visual estimation. QFR, quantitative coronary angiography (QCA), and wire-based FFR were assessed online in blinded fashion during coronary angiography and re-analyzed offline at an independent core laboratory. The primary endpoint was improved diagnostic accuracy of coronary angiography using QFR (hypothesized to be greater than the target goal of 75% at a two-sided significance level of 0.05).

Overall results showed patient-level and vessel-level diagnostic accuracy of QFR were 92.4% and 92.7%, respectively; exceeding the prespecified primary endpoint target value. Sensitivity in identifying hemodynamically-significant stenosis was significantly higher for QFR than QCA at 94.6% and 62.5%, respectively. Similarly, specificity in identifying hemodynamically-significant stenosis was also much higher for QFR at 91.7% vs 58.1%. Researchers also noted that positive predictive value, negative predictive value, positive likelihood ratio, and negative likelihood ratio for QFR was 85.5%, 97.1%, 11.4, and 0.06, respectively. Offline analysis showed vessel-level QFR had a high diagnostic accuracy of 93.3%.

In FAVOR II findings from Europe and Japan, QFR also showed superior sensitivity (88% vs 46%) and specificity (88% vs 77%) for detection of functional significant lesions in comparison with 2D-QCA using FFR as reference standard. Additionally, researchers noted "in-procedure QFR computation was feasible and was computed within the time of standard FFR measurements." However, they also said "randomized trials are required to determine if a QFR-based diagnostic strategy provides non-inferior clinical outcome compared to pressure wire based strategies."