title: Agreement between ambulatory, home, and office blood pressure variability.
abstract: OBJECTIVE
  Ambulatory, home, and office blood pressure (BP) variability are often treated as a single entity. Our aim was to assess the agreement between these three methods for measuring BP variability.
  
  
  METHODS
  Twenty-four-hour ambulatory BP monitoring, 28 home BP measurements, and eight office BP measurements were performed on 461 population-based or hypertensive participants. Five variability indices were calculated for all measurement methods: SD, coefficient of variation, maximum-minimum difference, variability independent of the mean, and average real variability. Pearson's correlation coefficients were calculated for indices measured with different methods. The agreement between different measurement methods on the diagnoses of extreme BP variability (participants in the highest decile of variability) was assessed with kappa (κ) coefficients.
  
  
  RESULTS
  SBP/DBP variability was greater in daytime (coefficient of variation: 9.8 ± 2.9/11.9 ± 3.6) and night-time ambulatory measurements (coefficient of variation: 8.6 ± 3.4/12.1 ± 4.5) than in home (coefficient of variation: 4.4 ± 1.8/4.7 ± 1.9) and office (coefficient of variation: 4.6 ± 2.4/5.2 ± 2.6) measurements (P < 0.001/0.001 for all). Pearson's correlation coefficients for systolic/diastolic daytime or night-time ambulatory-home, ambulatory-office, and home-office variability indices ranged between 0.07-0.25/0.12-0.23, 0.13-0.26/0.03-0.22 and 0.13-0.24/0.10-0.19, respectively, indicating, at most, a weak positive (r < 0.3) relationship. The agreement between measurement methods on diagnoses of extreme SBP/DBP variability was only slight (κ < 0.2), with the κ coefficients for daytime and night-time ambulatory-home, ambulatory-office, and home-office agreement varying between-0.014-0.20/0.061-0.15, 0.037-0.18/0.082-0.15, and 0.082-0.13/0.045-0.15, respectively.
  
  
  CONCLUSIONS
  Shorter-term and longer-term BP variability assessed by different methods of BP measurement seem to correlate only weakly with each other. Our study suggests that BP variability measured by different methods and timeframes may reflect different phenomena, not a single entity.
authors.affiliation: aDepartment of Health, National Institute for Health and Welfare bDepartment of Medicine cTyks and Turku Region Joint Emergency Services, Turku University Hospital, Turku, Finland.
authors.forename: Eeva P
authors.initials: EP
authors.lastname: Juhanoja
authors.forename: Teemu J
authors.initials: TJ
authors.lastname: Niiranen
authors.forename: Jouni K
authors.initials: JK
authors.lastname: Johansson
authors.forename: Pauli J
authors.initials: PJ
authors.lastname: Puukka
authors.forename: Antti M
authors.initials: AM
authors.lastname: Jula
mesh_terms: D000328:Adult; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory; D003971:Diastole; D005260:Female; D006801:Humans; D006973:Hypertension / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D009819:Office Visits; D012648:Self Care; D013599:Systole; D013997:Time Factors