title: Using the coronary artery calcium score to predict coronary heart disease events: a systematic review and meta-analysis.
abstract: BACKGROUND
  Primary prevention of coronary heart disease is most appropriate for patients at relatively high risk. Measurement of coronary artery calcium has been proposed as a way to improve risk assessment, but it is unknown whether it adds predictive information to standard risk factor assessment.
  
  
  METHODS
  We systematically searched electronic databases for relevant articles published between January 1, 1980, and March 19, 2003, and hand searched bibliographies. We included studies that reported measuring the coronary artery calcium score by electron beam computed tomography in asymptomatic subjects and subsequent follow-up of those patients for coronary events and that presented score-specific relative risks, adjusted for established risk factors. Two abstractors verified inclusion criteria and abstracted data from each study. We estimated adjusted relative risks associated with 3 standard categories of coronary artery calcium scores (1-100, 101-400, and >400), compared with a score of 0, and used a random-effects model for meta-analysis.
  
  
  RESULTS
  Meta-analysis of the 4 studies meeting inclusion criteria yielded a summary adjusted relative risk of 2.1 (95% confidence interval, 1.6-2.9) for a coronary artery calcium score of 1 to 100. Relative risk estimates for higher calcium scores were higher, ranging from 3.0 to 17.0 but varied significantly among studies. Subgroup analyses suggested that differences among studies in outcome adjudication (blinded or not), measurement of other risk factors (direct or by patient history), tomographic slice thickness (3 or 6 mm), and/or proportion of female study subjects may account for this heterogeneity.
  
  
  CONCLUSIONS
  The coronary artery calcium score is an independent predictor of coronary heart disease events.
authors.affiliation: Department of Epidemiology and Biostatistics, University of California, San Francisco, 500 Parnassus Ave, MU 420 West, Box 0560, San Francisco, CA 94143, USA. mpletcher@epi.ucsf.edu
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Pletcher
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Tice
authors.forename: Michael
authors.initials: M
authors.lastname: Pignone
authors.forename: Warren S
authors.initials: WS
authors.lastname: Browner
mesh_terms: D006801:Humans; D002118:Calcium / Q000378:metabolism; D003327:Coronary Disease / Q000453:epidemiology / Q000378:metabolism; D003331:Coronary Vessels / Q000737:chemistry / Q000473:pathology; D005500:Follow-Up Studies; D011237:Predictive Value of Tests; D012307:Risk Factors; D012680:Sensitivity and Specificity
chemical_list: D002118:Calcium