Ethnicity and differences between clinic and ambulatory blood pressure measurements.
BACKGROUND
This study investigated the relationship of ethnicity to the differences between blood pressure (BP) measured in a clinic setting and by ambulatory blood pressure monitoring (ABPM) in individuals with a previous diagnosis of hypertension (HT) and without a previous diagnosis of hypertension (NHT).


METHODS
A cross-sectional comparison of BP measurement was performed in 770 participants (white British (WB, 39%), South Asian (SA, 31%), and African Caribbean (AC, 30%)) in 28 primary care clinics in West Midlands, United Kingdom. Mean differences between daytime ABPM, standardized clinic (mean of 3 occasions), casual clinic (first reading on first occasion), and last routine BP taken at the general practitioner practice were compared in HT and NHT individuals.


RESULTS
Daytime systolic and diastolic ABPM readings were similar to standardized clinic BP (systolic: 128 (SE 0.9) vs. 125 (SE 0.9) mm Hg (NHT) and 132 (SE 0.7) vs. 131 (SE 0.7) mm Hg (HT)) and were not associated with ethnicity to a clinically important extent. When BP was taken less carefully, differences emerged: casual clinic readings were higher than ABPM, particularly in the HT group where the systolic differences approached clinical relevance (131 (SE 1.2) vs. 129 (SE 1.0) mm Hg (NHT) and 139 (SE 0.9) vs. 133 (SE 0.7) mm Hg (HT)) and were larger in SA and AC hypertensive individuals (136 (SE 1.5) vs. 133 (SE 1.2) mm Hg (WB), 141 (SE 1.7) vs. 133 (SE 1.4) mm Hg (SA), and 142 (SE 1.6) vs. 134 (SE 1.3) mm Hg (AC); mean differences: 3 (0-7), P = 0.03 and 4 (1-7), P = 0.01, respectively). Differences were also observed for the last practice reading in SA and ACs.


CONCLUSIONS
BP differences between ethnic groups where BP is carefully measured on multiple occasions are small and unlikely to alter clinical management. When BP is measured casually on a single occasion or in routine care, differences appear that could approach clinical relevance.
Clinical and Experimental Medicine, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham, UK; u.martin@bham.ac.uk.
Una
U
Martin
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
M Sayeed
MS
Haque
Primary Care Health Sciences, NIHR School for Primary Care Research, University of Oxford, Radcliffe Observatory Quarter, Oxford, UK;
Sally
S
Wood
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
Sheila M
SM
Greenfield
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
Paramjit S
PS
Gill
Primary Care Unit, University of Cambridge, Cambridge, UK;
Jonathan
J
Mant
School of Health Studies, University of Bradford, Bradford, UK.
Mohammed A
MA
Mohammed
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
Gurdip
G
Heer
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
Amanpreet
A
Johal
Primary Care Clinical Sciences, NIHR School for Primary Care Research, University of Birmingham, Edgbaston, Birmingham, UK;
Ramendeep
R
Kaur
Primary Care Health Sciences, NIHR School for Primary Care Research, University of Oxford, Radcliffe Observatory Quarter, Oxford, UK;
Claire
C
Schwartz
Primary Care Unit, University of Cambridge, Cambridge, UK;
Richard J
RJ
McManus
D000328:Adult; D000368:Aged; D000554:Ambulatory Care Facilities / Q000706:statistics & numerical data; D000959:Antihypertensive Agents / Q000627:therapeutic use; D001794:Blood Pressure / Q000187:drug effects; D018660:Blood Pressure Monitoring, Ambulatory / Q000379:methods / Q000706:statistics & numerical data; D005006:Ethnicity; D005260:Female; D006801:Humans; D006973:Hypertension / Q000175:diagnosis / Q000208:ethnology / Q000628:therapy; D008297:Male; D008875:Middle Aged; D010346:Patient Care Management; D010818:Practice Patterns, Physicians'; D006113:United Kingdom / Q000453:epidemiology
D000959:Antihypertensive Agents
ambulatory blood pressure monitoring; blood pressure; blood pressure determination; ethnic group; hypertension; systolic pressure; white coat hypertension.