Hypertension:

Blood Pressure Measurement and the

new NICE guidelineProf 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

Last_practice_systolic20019018017016015014013012011010090

Dotplot of Last_practice_systolic

Each symbol represents up to 4 observations.

Same population with routine and research measurement

Blood Pressure varies through the day and between seasons

Hypertension. 2006;47:155-161

occasion

systolic

654321

146

144

142

140

138

136

134

132

130

Interval Plot of systolic vs occasion95% CI for the Mean

occasions

diastolic

654321

83

82

81

80

79

78

77

Interval Plot of diastolic vs occasions95% CI for the Mean

Even on a single occasion BP drops

•Approx 1500 patients

•24 practices

•6 readings at 1min intervals

•12 mmHg systolic drop

•Stable after 5th reading

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

Journal of Hypertension 2004, 22:1099–1104

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

•Out of office measures allow better estimation of “usual blood pressure”

•Better correlated with prognosis

•Detection of White Coat (and masked) HT

BP measurement and diagnosis

Detection of white coat and masked HT requires out of office measurement

•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

BP measurement and diagnosis

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% andspecificity 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?

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 (1)

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

Diagnosing hypertension (2)

Care Pathway

CBPM ≥160/100 mmHg & ABPM/HBPM

≥ 150/95 mmHg

Stage 2 hypertension

Consider specialist referral

Offer antihypertensive drug treatment

Offer lifestyle interventions

If younger than 40 years

If target organ damage present or 10-year cardiovascular risk > 20%

Offer annual review of care to monitor blood pressure, provide support and discuss lifestyle, symptoms and medication

Offer patient education and interventions to support adherence to treatment

CBPM ≥140/90 mmHg & ABPM/HBPM ≥ 135/85 mmHg

Stage 1 hypertension

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 guidelineProf Richard McManus

BHS Annual Meeting Cambridge 2011

NICE clinical guideline 127