Hypertension:
Blood Pressure
Measurement and the
new NICE guideline
Prof Richard McManus
BHS Annual Meeting Cambridge 2011
NICE clinical guideline 127
Overview
•Blood Pressure Measurement – where are we now?
•Implications of measurement modalities on diagnosis
•Systematic Review of methods for diagnosing
hypertension
•Cost effectiveness modelling
•Guideline recommendations
•Issues and conclusions
BP Measurement
Routine measurement is often
flawed
Dotplot of Last_practice_systolic
Dotplot of systolic
90
100
110
120
130 140 150 160
Last_practice_systolic
170
180
190
200
Each symbol represents up to 4 observations.
Same population with routine and
research measurement
80
90
100 110 120 130 140 150 160 170 180 190 200 210 220 230 240
systolic
Each symbol represents up to 12 observations.
Blood Pressure varies through the day
and between seasons
Hypertension. 2006;47:155-161
Even on a single occasion BP
drops
Interval Plot of systolic vs occasion
•24 practices
144
142
140
systolic
•Approx 1500
patients
95% CI for the Mean
146
138
136
134
132
•6 readings at 1min
intervals
•Stable after
reading
5th
1
2
3
4
5
6
occasion
Interval Plot of diastolic vs occasions
95% CI for the Mean
83
82
81
diastolic
•12 mmHg systolic
drop
130
80
79
78
77
1
2
3
4
occasions
5
6
Family Practice 1997; 14:130-135
BP takes some
time to settle with
repeated
measurement
over
weeks/months
Causes of erroneous measurement
BMJ 2001;322;908-911
BP measurement and diagnosis
BP measurement and diagnosis
•Out of office measures:
• better estimation of “usual blood pressure”
• better correlated with prognosis
Ambulatory vs clinic for Prognosis
•2 pooled plus 11
individual studies
•ABPM superior to
clinic BP in predicting
CVD events
•Greater risk per
mmHg increase in
ABPM vs clinic
Hansen J Hyp 2007
Home vs clinic for prognosis
•4 studies
•2 biggest did not show
convincing additional
prognostic benefit from
home above office
• Some evidence from
smaller studies of
improvement from home
(esp DBP) but
underpowered
•Greater risk per mmHg
from home
Journal of Hypertension 2004, 22:1099–1104
BP measurement and diagnosis
•Out of office measures allow better
estimation of “usual blood pressure”
•Better correlated with prognosis
•Detection of White Coat (and masked) HT
Detection of white coat and masked HT
requires out of office measurement
BP measurement and diagnosis
•Out of office measures allow better
estimation of “usual blood pressure”
•Better correlated with prognosis
•Detection of White Coat (and masked) HT
•ABPM de facto gold standard for most
clinicians
• What you do when there is uncertainty
How do clinic and out of office
measurements compare?
•Reviewed literature: 2914 studies of which
20 were relevant
•7 compared ABPM with clinic monitoring for
diagnosis
•3 compared HBPM with clinic monitoring for
diagnosis
•Full details:
BMJ 2011;342:d3621 doi: 10.1136/bmj.d3621
Many people currently
potentially misdiagnosed...
Worse if only studies around diagnostic
threshold used:
sensitivity of 86% and
specificity of 46%
What about Home Monitoring?
Relative sensitivity and
specificity of clinic and
home measurement vs
ABPM
What threshold ABPM ?
Based on Head et al BMJ 2010
•adjust by 5/5 mmHg at lower threshold
(stage 1 hypertension, 140/90 mmHg clinic)
• ie < 135/85 mm Hg
•10/5 mmHg at higher threshold
(stage 2 hypertension, 160/100 mmHg clinic)
• Ie < 150/95 mmHg
International Thresholds for
hypertension diagnosis
(Mean
daytime BP)
How many Home measurements?
Conclusion = at least 4 days monitoring and discard 1st
What about costs?
Is Out of Office Diagnosis cost
effective?
•Modelling to evaluate the most cost-effective
method of confirming a diagnosis of
hypertension in a population suspected of
having hypertension
•ABPM vs Home vs clinic
•Further details Lovibond et al, Lancet 2011
Markov Model
•Health and personal social services perspective
•Lifetime horizon
•Assume all have raised clinic screening
•People aged 40 and over
Markov Model
•Costs from published sources and NHS
•Test performance from systematic review
•Risk calculated using Framingham equation
Results
•ABPM most cost effective for every age group
Results
•ABPM most cost effective for every age group
•Robust to wide range of sensitivity analyses
Results – sensitivity analysis
Results
•ABPM most cost effective for every age group
•Robust to wide range of sensitivity analyses
•Sensitive to
• Assumption of equal test performance
• Assumption of no effect of Rx below
140/90 mmHg
HOW DOES THIS TRANSLATE
TO RECOMMENDATIONS?
Diagnosing hypertension (1)
If the clinic blood
pressure is
140/90 mmHg or higher,
offer ambulatory blood
pressure monitoring
(ABPM) to confirm the
diagnosis of hypertension
Diagnosing hypertension (2)
When using the following to confirm diagnosis ensure:
ABPM:
– two measurements per hour during the person’s usual
waking hours (Day time mean)
HBPM:
– two consecutive seated measurements, at least 1
minute apart
– blood pressure is recorded twice a day and for at least
4 days
– measurements on the first day are discarded –
average value of all remaining is used
CBPM ≥140/90 mmHg
& ABPM/HBPM
≥ 135/85 mmHg
CBPM ≥160/100 mmHg
& ABPM/HBPM
≥ 150/95 mmHg
Stage 1 hypertension
Stage 2 hypertension
If target organ damage present or
10-year cardiovascular risk > 20%
If younger than 40 years
Care Pathway
Offer antihypertensive
drug treatment
Consider specialist
referral
Offer lifestyle interventions
Offer patient education and interventions to support adherence to treatment
Offer annual review of care to monitor blood pressure, provide support and
discuss lifestyle, symptoms and medication
ABPM issues
•Won’t upfront costs be very expensive?
•Will my (specialist) service be over run?
•ABPM vs home choice
Conclusions
•Diagnosis of Hypertension is changing
•Implementation challenging but benefits
can be realised in terms of better targeting
of treatment and reduced costs
Hypertension:
Blood Pressure
Measurement and the
new NICE guideline
Prof Richard McManus
BHS Annual Meeting Cambridge 2011
NICE clinical guideline 127