title: Reference intervals for common carotid intima-media thickness measured with echotracking: relation with risk factors.
abstract: OBJECTIVE
  Common carotid artery intima-media thickness (CCIMT) is widely used as a surrogate marker of atherosclerosis, given its predictive association with cardiovascular disease (CVD). The interpretation of CCIMT values has been hampered by the absence of reference values, however. We therefore aimed to establish reference intervals of CCIMT, obtained using the probably most accurate method at present (i.e. echotracking), to help interpretation of these measures.
  
  
  RESULTS
  We combined CCIMT data obtained by echotracking on 24 871 individuals (53% men; age range 15-101 years) from 24 research centres worldwide. Individuals without CVD, cardiovascular risk factors (CV-RFs), and BP-, lipid-, and/or glucose-lowering medication constituted a healthy sub-population (n = 4234) used to establish sex-specific equations for percentiles of CCIMT across age. With these equations, we generated CCIMT Z-scores in different reference sub-populations, thereby allowing for a standardized comparison between observed and predicted ('normal') values from individuals of the same age and sex. In the sub-population without CVD and treatment (n = 14 609), and in men and women, respectively, CCIMT Z-scores were independently associated with systolic blood pressure [standardized βs 0.19 (95% CI: 0.16-0.22) and 0.18 (0.15-0.21)], smoking [0.25 (0.19-0.31) and 0.11 (0.04-0.18)], diabetes [0.19 (0.05-0.33) and 0.19 (0.02-0.36)], total-to-HDL cholesterol ratio [0.07 (0.04-0.10) and 0.05 (0.02-0.09)], and body mass index [0.14 (0.12-0.17) and 0.07 (0.04-0.10)].
  
  
  CONCLUSIONS
  We estimated age- and sex-specific percentiles of CCIMT in a healthy population and assessed the association of CV-RFs with CCIMT Z-scores, which enables comparison of IMT values for (patient) groups with different cardiovascular risk profiles, helping interpretation of such measures obtained both in research and clinical settings.
authors.affiliation: Department of Pharmacology and INSERM U970, Hôpital Européen Georges Pompidou, Paris, France.
authors.forename: Lian
authors.initials: L
authors.lastname: Engelen
authors.forename: Isabel
authors.initials: I
authors.lastname: Ferreira
authors.forename: Coen D
authors.initials: CD
authors.lastname: Stehouwer
authors.forename: Pierre
authors.initials: P
authors.lastname: Boutouyrie
authors.forename: Stéphane
authors.initials: S
authors.lastname: Laurent
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D050197:Atherosclerosis / Q000000981:diagnostic imaging*; D059168:Carotid Intima-Media Thickness / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D012016:Reference Values; D012307:Risk Factors; D055815:Young Adult