title: Comparisons of established risk prediction models for cardiovascular disease: systematic review.
abstract: OBJECTIVE
  To evaluate the evidence on comparisons of established cardiovascular risk prediction models and to collect comparative information on their relative prognostic performance.
  
  
  METHODS
  Systematic review of comparative predictive model studies.
  
  
  METHODS
  Medline and screening of citations and references.
  
  
  METHODS
  Studies examining the relative prognostic performance of at least two major risk models for cardiovascular disease in general populations.
  
  
  METHODS
  Information on study design, assessed risk models, and outcomes. We examined the relative performance of the models (discrimination, calibration, and reclassification) and the potential for outcome selection and optimism biases favouring newly introduced models and models developed by the authors.
  
  
  RESULTS
  20 articles including 56 pairwise comparisons of eight models (two variants of the Framingham risk score, the assessing cardiovascular risk to Scottish Intercollegiate Guidelines Network to assign preventative treatment (ASSIGN) score, systematic coronary risk evaluation (SCORE) score, Prospective Cardiovascular Münster (PROCAM) score, QRESEARCH cardiovascular risk (QRISK1 and QRISK2) algorithms, Reynolds risk score) were eligible. Only 10 of 56 comparisons exceeded a 5% relative difference based on the area under the receiver operating characteristic curve. Use of other discrimination, calibration, and reclassification statistics was less consistent. In 32 comparisons, an outcome was used that had been used in the original development of only one of the compared models, and in 25 of these comparisons (78%) the outcome-congruent model had a better area under the receiver operating characteristic curve. Moreover, authors always reported better area under the receiver operating characteristic curves for models that they themselves developed (in five articles on newly introduced models and in three articles on subsequent evaluations).
  
  
  CONCLUSIONS
  Several risk prediction models for cardiovascular disease are available and their head to head comparisons would benefit from standardised reporting and formal, consistent statistical comparisons. Outcome selection and optimism biases apparently affect this literature.
authors.affiliation: Department of Hygiene and Epidemiology, University of Ioannina School of Medicine, Ioannina, Greece.
authors.forename: George C M
authors.initials: GC
authors.lastname: Siontis
authors.forename: Ioanna
authors.initials: I
authors.lastname: Tzoulaki
authors.forename: Konstantinos C
authors.initials: KC
authors.lastname: Siontis
authors.forename: John P A
authors.initials: JP
authors.lastname: Ioannidis
mesh_terms: D000465:Algorithms; D002318:Cardiovascular Diseases / Q000175:diagnosis* / Q000209:etiology*; D006801:Humans; D008962:Models, Theoretical; D011237:Predictive Value of Tests; D011379:Prognosis; D012372:ROC Curve; D018570:Risk Assessment