Objectives: 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.
Conclusion: 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.
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
Correspondence to Richard J. McManus, Nuffield Department of Primary Care Health Sciences, University of Oxford; Radcliffe Observatory Quarter, Woodstock Road, Oxford OX2 6GG, UK. Tel: +44 1865 617834; fax: +44 1865 289287; e-mail: firstname.lastname@example.org
Abbreviations: AUC, area under the curve; BP, blood pressure; HBP, home blood pressure; NPV, negative predictive value; PPV, positive predictive value; TASMINH2, Telemonitoring and Self-management in the Control of Hypertension 2
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Received February 21, 2014
Received in revised form June 27, 2014
Accepted June 27, 2014