title: Blood pressure measurement method and inter-arm differences: a meta-analysis.
abstract: BACKGROUND
  Screening for inter-arm difference (IAD) of blood pressure (BP) at each first visit is recommended by numerous guidelines whereas it is unclear whether the method by which IAD is measured has significant influence on the IAD value.
  
  
  METHODS
  A systematic review is made of the studies reporting on double-arm measurements and the association of IAD with procedure characteristics (Medline/PubMed, Embase, and Cochrane Library).
  
  
  RESULTS
  The mean absolute IAD was 5.4 ± 1.7 and 3.6 ± 1.2 mm Hg for systolic and diastolic BP, respectively. Of all subjects 14% had a systolic IAD ≥10 mm Hg, 4% a systolic IAD ≥20 mm Hg, and 7% a diastolic IAD ≥10 mm Hg. The relative risk (RR) of obtaining a systolic IAD ≥10 and 20 mm Hg and a diastolic IAD ≥10 mm Hg is higher when measuring sequentially instead of simultaneously (2.2 (95% CI: 1.4-3.6), P < 0.01; 4.8 (95% CI: 1.1-21.9), P < 0.05 and 2.5 (95% CI: 1.0-6.3) P < 0.05, respectively), when using a manual instead of an automated device (2.1 (95% CI: 1.1-3.9), P < 0.05; 4.4 (95% CI: 1.8-10.8), P < 0.01 and 3.7 (95% CI: 1.6-8.6), P < 0.01, respectively) and when performing only one BP measurement instead of multiple (2.0 (95% CI: 1.1-3.8), P < 0.05; 4.3 (95% CI: 1.6-11.4), P < 0.01 and 4.4 (95% CI: 1.7-11.4), P < 0.01, respectively).
  
  
  CONCLUSIONS
  Screening for IAD of BP is important but the measurement methodology has a major influence on IAD results. To prevent overestimation and observer bias IAD should be assessed simultaneously at both arms, with one or two automatic devices and multiple readings should be taken.
authors.affiliation: Microlife Corporation, Taipei, Taiwan. Willem.verberk@microlife.ch
authors.forename: Willem J
authors.initials: WJ
authors.lastname: Verberk
authors.forename: Alfons G H
authors.initials: AG
authors.lastname: Kessels
authors.forename: Theo
authors.initials: T
authors.lastname: Thien
mesh_terms: D000328:Adult; D000368:Aged; D001132:Arm / Q000502:physiology*; D001314:Auscultation / Q000295:instrumentation; D001331:Automation; D001795:Blood Pressure Determination / Q000295:instrumentation / Q000379:methods*; D003971:Diastole; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D015588:Observer Variation; D009991:Oscillometry / Q000295:instrumentation; D013599:Systole