Diagnostic comparison of automatic and manual TIMI frame-counting-generated quantitative flow ratio (QFR) values

Quantitative flow ratio (QFR) is a computational measurement of FFR (fractional flow reserve), calculated from coronary angiography. Latest QFR software automates TIMI frame counting (TFC), which occurs during the flow step of QFR analyses, making the analysis faster and more reproducible. The objective is to determine the diagnostic performance of QFR values obtained from analyses using automatic TFC compared to those obtained from analyses using manual TFC. This was a single-arm clinical trial that used the prospective analysis of the coronary angiographic image series of 97 patients who underwent evaluation of stable coronary artery disease with FFR/iFR at MedStar Washington Hospital Center in Washington, DC, USA. Automatic and manual TFC QFR values were obtained from the analyses of each of the 97 patients' image series, with manual TFC QFR values as the current gold standard for comparison. The diagnostic performance of automatic TFC QFR values was measured as follows: sensitivity was 0.87 (95% CI 0.66-0.97) and specificity was 1.00 (95% CI 0.9514-1.00), positive predictive value (PPV) was 1.00 (95%CI 1.00-1.00), while the NPV was 0.96 (95% CI 0.96-0.99). Overall accuracy was 96.91% (95% CI 91.23%-99.36%). The agreement as illustrated by the Bland-Altman plot shows a bias of 0.0023 (SD 0.0208) and narrow limits of agreement (LOA): Upper LOA 0.0573 and Lower LOA - 0.0528. The area under curve (AUC) was 0.996. QFR values generated from automatic TFC are comparable to those generated from manual TFC in diagnostic capability. The most recent software update produces values equivalent to those of the previous manual option, and can therefore be used interchangeably.