title: Danish study of Non-Invasive testing in Coronary Artery Disease (Dan-NICAD): study protocol for a randomised controlled trial.
abstract: Coronary computed tomography angiography (CCTA) is an established method for ruling out coronary artery disease (CAD). Most patients referred for CCTA do not have CAD and only approximately 20-30 % of patients are subsequently referred to further testing by invasive coronary angiography (ICA) or non-invasive perfusion evaluation due to suspected obstructive CAD. In cases with severe calcifications, a discrepancy between CCTA and ICA often occurs, leading to the well-described, low-diagnostic specificity of CCTA. As ICA is cost consuming and involves a risk of complications, an optimized algorithm would be valuable and could decrease the number of ICAs that do not lead to revascularization. The primary objective of the Dan-NICAD study is to determine the diagnostic accuracy of cardiac magnetic resonance imaging (CMRI) and myocardial perfusion scintigraphy (MPS) as secondary tests after a primary CCTA where CAD could not be ruled out. The secondary objective includes an evaluation of the diagnostic precision of an acoustic technology that analyses the sound of coronary blood flow. It may potentially provide better stratification prior to CCTA than clinical risk stratification scores alone.
  
  
  
  Dan-NICAD is a multi-centre, randomised, cross-sectional trial, which will include approximately 2,000 patients without known CAD, who were referred to CCTA due to a history of symptoms suggestive of CAD and a low-risk to intermediate-risk profile, as evaluated by a cardiologist. Patient interview, sound recordings, and blood samples are obtained in connection with the CCTA. All patients with suspected obstructive CAD by CCTA are randomised to either stress CMRI or stress MPS, followed by ICA with fractional flow reserve (FFR) measurements. Obstructive CAD is defined as an FFR below 0.80 or as high-grade stenosis (>90 % diameter stenosis) by visual assessment. Diagnostic performance is evaluated as sensitivity, specificity, predictive values, likelihood ratios, and C statistics. Enrolment commenced in September 2014 and is expected to be complete in May 2016.
  
  
  
  Dan-NICAD is designed to assess whether a secondary perfusion examination after CCTA could safely reduce the number of ICAs where revascularization is not required. The results are expected to add knowledge about the optimal algorithm for diagnosing CAD.
  
  
  
  Clinicaltrials.gov identifier, NCT02264717 . Registered on 26 September 2014.
authors.affiliation: Department of Internal Medicine, Hospital Unit West, Gl.landevej 61, 7400, Herning, Denmark. lounisse@rm.dk.
authors.forename: Louise
authors.initials: L
authors.lastname: Nissen
authors.affiliation: Department of Internal Medicine, Hospital Unit West, Gl.landevej 61, 7400, Herning, Denmark.|Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Simon
authors.initials: S
authors.lastname: Winther
authors.affiliation: Department of Radiology, Regional Hospital of Silkeborg, Silkeborg, Denmark.
authors.forename: Christin
authors.initials: C
authors.lastname: Isaksen
authors.affiliation: Department of Nuclear Medicine, Hospital Unit West, Herning, Denmark.
authors.forename: June Anita
authors.initials: JA
authors.lastname: Ejlersen
authors.affiliation: Department of Radiology, Regional Hospital of Silkeborg, Silkeborg, Denmark.
authors.forename: Lau
authors.initials: L
authors.lastname: Brix
authors.affiliation: Department of Cardiology, Regional Hospital of Silkeborg, Silkeborg, Denmark.
authors.forename: Grazina
authors.initials: G
authors.lastname: Urbonaviciene
authors.affiliation: Department of Cardiology, Regional Hospital of Silkeborg, Silkeborg, Denmark.
authors.forename: Lars
authors.initials: L
authors.lastname: Frost
authors.affiliation: Department of Internal Medicine, Hospital Unit West, Gl.landevej 61, 7400, Herning, Denmark.
authors.forename: Lene Helleskov
authors.initials: LH
authors.lastname: Madsen
authors.affiliation: Department of Internal Medicine, Hospital Unit West, Gl.landevej 61, 7400, Herning, Denmark.
authors.forename: Lars Lyhne
authors.initials: LL
authors.lastname: Knudsen
authors.affiliation: Department of Health Science and Technology, Aalborg University, Aalborg, Denmark.
authors.forename: Samuel Emil
authors.initials: SE
authors.lastname: Schmidt
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Niels Ramsing
authors.initials: NR
authors.lastname: Holm
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Michael
authors.initials: M
authors.lastname: Maeng
authors.affiliation: Department of Biomedicine, Aarhus University, Aarhus, Denmark.
authors.forename: Mette
authors.initials: M
authors.lastname: Nyegaard
authors.affiliation: Department of Cardiology, Aarhus University Hospital, Aarhus, Denmark.
authors.forename: Hans Erik
authors.initials: HE
authors.lastname: Bøtker
authors.affiliation: Department of Internal Medicine, Hospital Unit West, Gl.landevej 61, 7400, Herning, Denmark.
authors.forename: Morten
authors.initials: M
authors.lastname: Bøttcher
mesh_terms: D002985:Clinical Protocols; D000072226:Computed Tomography Angiography; D017023:Coronary Angiography; D003324:Coronary Artery Disease / Q000000981:diagnostic imaging*; D003430:Cross-Sectional Studies; D053805:Fractional Flow Reserve, Myocardial; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging
keywords: Cardiac magnetic resonance imaging; Coronary angiography; Coronary artery disease; Coronary computed tomography angiography; Fractional flow reserve; Myocardial perfusion scintigraphy