title: Diagnostic accuracy and discrimination of ischemia by fractional flow reserve CT using a clinical use rule: results from the Determination of Fractional Flow Reserve by Anatomic Computed Tomographic Angiography study.
abstract: BACKGROUND
  Fractional flow reserve (FFR) is the gold standard for determining lesion-specific ischemia. Computed FFRCT derived from coronary CT angiography (coronary CTA) correlates well with invasive FFR and accurately differentiates between ischemia-producing and nonischemic lesions. The diagnostic performance of FFRCT when applied in a clinically relevant way to all vessels ≥ 2 mm in diameter stratified by sex and age has not been previously examined.
  
  
  METHODS
  Two hundred fifty-two patients and 407 vessels underwent coronary CTA, FFRCT, invasive coronary angiography, and invasive FFR. FFRCT and FFR ≤ 0.80 were considered ischemic, whereas CT stenosis ≥ 50% was considered obstructive. The diagnostic performance of FFRCT was assessed following a prespecified clinical use rule which included all vessels ≥ 2 mm in diameter, not just those assessed by invasive FFR measurements. Stenoses <30% were assigned an FFR of 0.90, and stenoses >90% were assigned an FFR of 0.50. Diagnostic performance of FFRCT was stratified by vessel diameter, sex, and age.
  
  
  RESULTS
  By FFR, ischemia was identified in 129 of 252 patients (51%) and in 151 of 407 vessels (31%). Mean age (± standard deviation) was 62.9 ± 9 years, and women were older (65.5 vs 61.9 years; P = .003). Per-patient diagnostic accuracy (83% vs 72%; P < .005) and specificity (54% vs 82%, P < .001) improved significantly after application of the clinical use tool. These were significantly improved over standard coronary CTA values before application of the clinical use rule. Discriminatory power of FFRCT also increased compared with baseline (area under the receiver operating characteristics curve [AUC]: 0.93 vs 0.81, P < .001). Diagnostic performance improved in both sexes with no significant differences between the sexes (AUC: 0.93 vs 0.90, P = .43). There were no differences in the discrimination of FFRCT after application of the clinical use rule when stratified by age ≥ 65 or <65 years (AUC: 0.95 vs 0.90, P = .10).
  
  
  CONCLUSIONS
  The diagnostic accuracy and discriminatory power of FFRCT improve significantly after the application of a clinical use rule which includes all clinically relevant vessels >2 mm in diameter. FFRCT has similar diagnostic accuracy and discriminatory power for ischemia detection in men and women irrespective of age using a cut point of 65 years.
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada. Electronic address: angus_thommo@hotmail.com.
authors.forename: Angus G
authors.initials: AG
authors.lastname: Thompson
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Rekha
authors.initials: R
authors.lastname: Raju
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Philipp
authors.initials: P
authors.lastname: Blanke
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Tae-Hyun
authors.initials: TH
authors.lastname: Yang
authors.affiliation: Department of Medicine, University of British Columbia, Vancouver, BC, Canada.
authors.forename: Giovanni Battista John
authors.initials: GB
authors.lastname: Mancini
authors.affiliation: Department of Medicine, Harbor UCLA Medical Center, Los Angeles, California.
authors.forename: Matthew J
authors.initials: MJ
authors.lastname: Budoff
authors.affiliation: Department of Cardiology B, Aarhus University Hospital Skejby, Palle Juul-Jensens Boulevard 99, 8200, Aarhus N, Denmark.
authors.forename: Bjarne L
authors.initials: BL
authors.lastname: Norgaard
authors.affiliation: Department of Radiology, New York-Presbyterian Hospital and the Weill Cornell Medical College, New York, NY, USA.
authors.forename: James K
authors.initials: JK
authors.lastname: Min
authors.affiliation: Department of Radiology, St Paul's Hospital, University of British Columbia, 1081 Burrard Street, Vancouver, BC, V6Z 1Y6, Canada.
authors.forename: Jonathon A
authors.initials: JA
authors.lastname: Leipsic
mesh_terms: D000367:Age Factors; D000368:Aged; D019540:Area Under Curve; D015331:Cohort Studies; D017023:Coronary Angiography / Q000379:methods*; D003324:Coronary Artery Disease / Q000175:diagnosis / Q000000981:diagnostic imaging*; D005260:Female; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D008297:Male; D008875:Middle Aged; D017202:Myocardial Ischemia / Q000175:diagnosis; D011446:Prospective Studies; D018570:Risk Assessment; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D012737:Sex Factors; D014057:Tomography, X-Ray Computed / Q000379:methods*
keywords: Computational fluid dynamics; Coronary CT angiography; Fractional flow reserve