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Observational Study
. 2014 Nov;32(11):2171-8; discussion 2178.
doi: 10.1097/HJH.0000000000000319.

Predicting out-of-office blood pressure level using repeated measurements in the clinic: an observational cohort study

James P Sheppard  1 , Roger Holder, Linda Nichols, Emma Bray, F D Richard Hobbs, Jonathan Mant, Paul Little, Bryan Williams, Sheila Greenfield, Richard J McManus
Affiliations
Free PMC article
Observational Study

Predicting out-of-office blood pressure level using repeated measurements in the clinic: an observational cohort study

James P Sheppard et al. J Hypertens. 2014 Nov.
Free PMC article

Abstract

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.

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Figures

FIGURE 1
FIGURE 1
Scatter plots showing the correlation between home–clinic SBP difference and the blood pressure drop, slope and quadratic coefficients of SBP measurements in the clinic.
FIGURE 2
FIGURE 2
Mean (± 95% confidence intervals) SBP for each clinic reading in white-coat, normal and masked effect groups. SBP1-6, clinic SBP readings 1–6. HBP, mean home blood pressure ± 95% confidence intervals; this differed between each group (white-coat group: 138 mmHg, 95% CI 137, 140 mmHg; normal group: 146 mmHg, 95% CI 145, 147 mmHg; masked group: 160 mmHg, 95% CI 158, 161 mmHg) because each was defined on the basis of the home–clinic blood pressure difference.
Box 1
Box 1
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Box 2
Box 2
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