title: Diagnostic accuracy and impact of computed tomographic coronary angiography on utilization of invasive coronary angiography.
abstract: BACKGROUND
  Computed tomographic coronary angiography (CTA), given its high negative predictive value, is a potential gatekeeper for invasive coronary angiography (ICA). Before CTA can be further accepted into clinical practice, its impact on healthcare resources needs to be better understood. We sought to determine the clinical impact of CTA on ICA referrals, CTA accuracy, and normalcy rate.
  
  
  RESULTS
  To determine the impact of CTA, consecutive patients (n=7017) undergoing ICA before and after implementing a dedicated cardiac CT program were reviewed and compared with 3 other centers (n=11 508). To determine CTA accuracy, we evaluated consecutive CTA patients who underwent ICA. For normalcy rate, we identified patients with a low pretest probability for obstructive coronary artery disease. With the implementation of a cardiac CT program, the frequency of normal ICA decreased from 31.5% (1114 of 3538 patients) to 26.8% (932 of 3479 patients) (P<0.001). These findings were significantly different (P=0.003) from the 3 centers, in which normal ICAs were unchanged (30.0% [1870 of 6224 patients] to 31.0% [1642 of 5284 patients]). CTA had excellent per-patient sensitivity (99% [CI, 95% to 100%]), positive predictive value (92% [CI, 86% to 96%]) and negative predictive value (95% [CI, 72% to 100%]). Because of referral bias, specificity (64% [CI, 44% to 81%]) was low; however, the normalcy rate of CTA was 94% (CI, 90% to 97%). After adjusting for referral bias, the adjusted sensitivity was 90% (CI, 89% to 91%), and the adjusted specificity was 95% (CI, 94% to 96%), with positive and negative predictive values of 92% (CI, 91% to 93%) and 93% (CI, 92% to 94%), respectively.
  
  
  CONCLUSIONS
  The clinical implementation of CTA appears to positively impact ICA by reducing the frequency of normal ICA. The operating characteristics of CTA support its potential role as a tool useful in ruling out obstructive coronary artery disease.
authors.affiliation: Department of Medicine, University of Ottawa Heart Institute, Ottawa, Ontario, Canada. bchow@ottawaheart.ca
authors.forename: Benjamin J W
authors.initials: BJ
authors.lastname: Chow
authors.forename: Arun
authors.initials: A
authors.lastname: Abraham
authors.forename: George A
authors.initials: GA
authors.lastname: Wells
authors.forename: Li
authors.initials: L
authors.lastname: Chen
authors.forename: Terrence D
authors.initials: TD
authors.lastname: Ruddy
authors.forename: Yeung
authors.initials: Y
authors.lastname: Yam
authors.forename: Nayia
authors.initials: N
authors.lastname: Govas
authors.forename: Phoebe Diane
authors.initials: PD
authors.lastname: Galbraith
authors.forename: Carole
authors.initials: C
authors.lastname: Dennie
authors.forename: Rob S
authors.initials: RS
authors.lastname: Beanlands
mesh_terms: D000368:Aged; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed