title: Center effect on ankle-brachial index measurement when using the reference method (Doppler and manometer): results from a large cohort study.
abstract: BACKGROUND
  The ankle-brachial index (ABI) is a simple and noninvasive tool used to detect peripheral arterial disease (PAD). We aimed to assess, in a French multicenter cohort, the center effect associated with arterial pressure (AP) and ABI measurements using the reference method and using a semiautomatic device.
  
  
  METHODS
  This study included baseline and 9-year follow-up data from 3,664 volunteers of 10 health examination centers of the DESIR (Data from an Epidemiological Study on the Insulin Resistance) syndrome French cohort. Ankle and brachial AP were measured at inclusion by the reference method (a mercury sphygmomanometer coupled with a Doppler probe for ankle measurements) and at 9 years by a semiautomatic device (Omron HEM-705CP). The center effect was assessed by the intraclass correlation coefficient (ICC), ratio of the between-center variance to the total variance of the measurement.
  
  
  RESULTS
  At inclusion, the sample mean age was 47.5 (s.d. 9.9) years; 49.3% were men. Although ICCs were smaller than 0.05 for brachial AP measurements, they were close to 0.18 and 0.20 for ankle systolic AP (SAP) and ABI measurements, respectively, when the reference method was used. No center effect for measures other than ankle SAP was detected. With the semiautomatic device method, all ICCs, including those for ankle SAP and ABI measurements, were between 0.005 and 0.04.
  
  
  CONCLUSIONS
  We found an important center effect on ABI measured with a sphygmomanometer and a Doppler probe but not a semiautomatic device. A center effect should be taken into account when planning any multicenter study on ABI measurement.
authors.affiliation: INSERM, CIC 202, Tours, France. vierron@univ-tours.fr
authors.forename: Emilie
authors.initials: E
authors.lastname: Vierron
authors.forename: Jean-Michel
authors.initials: JM
authors.lastname: Halimi
authors.forename: Jean
authors.initials: J
authors.lastname: Tichet
authors.forename: Beverley
authors.initials: B
authors.lastname: Balkau
authors.forename: Joel
authors.initials: J
authors.lastname: Cogneau
authors.forename: Bruno
authors.initials: B
authors.lastname: Giraudeau
mesh_terms: D000328:Adult; D000368:Aged; D000842:Ankle / Q000098:blood supply / Q000000981:diagnostic imaging; D055109:Ankle Brachial Index; D001795:Blood Pressure Determination / Q000379:methods*; D001916:Brachial Artery; D015331:Cohort Studies; D005260:Female; D006801:Humans; D008297:Male; D008365:Manometry; D008875:Middle Aged; D016491:Peripheral Vascular Diseases / Q000175:diagnosis*; D015203:Reproducibility of Results; D019722:Sphygmomanometers; D018608:Ultrasonography, Doppler