title: Predicting out-of-office blood pressure level using repeated measurements in the clinic: an observational cohort study.
abstract: OBJECTIVE
  Identification of people with lower (white-coat effect) or higher (masked effect) blood pressure at home compared to the clinic usually requires ambulatory or home monitoring. This study assessed whether changes in SBP with repeated measurement at a single clinic predict subsequent differences between clinic and home measurements.
  
  
  METHODS
  This study used an observational cohort design and included 220 individuals aged 35-84 years, receiving treatment for hypertension, but whose SBP was not controlled. The characteristics of change in SBP over six clinic readings were defined as the SBP drop, the slope and the quadratic coefficient using polynomial regression modelling. The predictive abilities of these characteristics for lower or higher home SBP readings were investigated with logistic regression and repeated operating characteristic analysis.
  
  
  RESULTS
  The single clinic SBP drop was predictive of the white-coat effect with a sensitivity of 90%, specificity of 50%, positive predictive value of 56% and negative predictive value of 88%. Predictive values for the masked effect and those of the slope and quadratic coefficient were slightly lower, but when the slope and quadratic variables were combined, the sensitivity, specificity, positive and negative predictive values for the masked effect were improved to 91, 48, 24 and 97%, respectively.
  
  
  CONCLUSIONS
  Characteristics obtainable from multiple SBP measurements in a single clinic in patients with treated hypertension appear to reasonably predict those unlikely to have a large white-coat or masked effect, potentially allowing better targeting of out-of-office monitoring in routine clinical practice.
authors.affiliation: aNuffield Department of Primary Care Health Sciences, University of Oxford bNational Institute for Health Research School for Primary Care Research, Radcliffe Observatory Quarter, Woodstock Road, Oxford cPrimary Care Clinical Sciences, University of Birmingham, Edgbaston, Birmingham dSchool of Psychology, Darwin Building, University of Central Lancashire, Preston, Lancashire ePrimary Care Unit, Institute of Public Health, University of Cambridge, Cambridge, Cambridgeshire fSchool of Medicine, University of Southampton, University Road, Southampton gInstitute of Cardiovascular Sciences, University College London (UCL) and National Institute for Health Research UCL Hospitals Biomedical Research Centre, London, UK.
authors.forename: James P
authors.initials: JP
authors.lastname: Sheppard
authors.forename: Roger
authors.initials: R
authors.lastname: Holder
authors.forename: Linda
authors.initials: L
authors.lastname: Nichols
authors.forename: Emma
authors.initials: E
authors.lastname: Bray
authors.forename: F D Richard
authors.initials: FD
authors.lastname: Hobbs
authors.forename: Jonathan
authors.initials: J
authors.lastname: Mant
authors.forename: Paul
authors.initials: P
authors.lastname: Little
authors.forename: Bryan
authors.initials: B
authors.lastname: Williams
authors.forename: Sheila
authors.initials: S
authors.lastname: Greenfield
authors.forename: Richard J
authors.initials: RJ
authors.lastname: McManus
mesh_terms: D000328:Adult; D000368:Aged; D000554:Ambulatory Care Facilities; D001794:Blood Pressure; D018660:Blood Pressure Monitoring, Ambulatory / Q000523:psychology*; D015331:Cohort Studies; D005260:Female; D006801:Humans; D016015:Logistic Models; D008297:Male; D059468:Masked Hypertension / Q000175:diagnosis* / Q000523:psychology; D008875:Middle Aged; D012680:Sensitivity and Specificity; D059466:White Coat Hypertension / Q000175:diagnosis* / Q000523:psychology