3.  Screening for Hypertension

 RECOMMENDATION

Screening for hypertension is recommended for all children and adults
(see Clinical Intervention ).
 
Burden of Suffering

Hypertension is usually defined as a diastolic blood pressure of 90 mm
Hg or higher or a systolic pressure of 140 mm Hg or higher.[1] It is
present in an estimated 43 million Americans and is more common in
blacks and older adults.[1a] Hypertension is a leading risk factor for
coronary heart disease, congestive heart failure, stroke, ruptured
aortic aneurysm, renal disease, and retinopathy.  These complications of
hypertension are among the most common and serious diseases in the U.S.,
and successful efforts to lower blood pressure could thus have
substantial impact on population morbidity and mortality.  Heart disease
is the leading cause of death in the U.S., accounting for nearly 740,000
deaths each year (287 deaths per 100,000 population), and
cerebrovascular disease, the third leading cause of death, accounts for
about 150,000 deaths each year (58/100,000).[2] Milder forms of
hypertension predict progression to more severe elevations and
development of cardiovascular disease.[1,3,4] Coronary heart disease
mortality begins to increase at systolic blood pressures above 110 mm Hg
and at diastolic pressures above 70 mm Hg.[5] The prevalence of
unrecognized and uncontrolled hypertension, and the mortality from
cardiovascular disease, have declined substantially in the U.S.  in the
past several decades.[1]

Treatable (also known as secondary) causes of hypertension such as
aortic coarctation or renovascular disease also may be associated with
severe consequences, including congestive heart failure, aortic rupture,
or stroke.[6-9] There are no population data available for estimating
the true prevalence of secondary hypertension.  The incidence of
coarctation of the aorta has been estimated at 0.2-0.6/1,000 live births
and the prevalence at 0.1-0.5/1,000 children.[10-12]

Accuracy of Screening Tests

The most accurate devices for measuring blood pressure (e.g., intra-
arterial catheters) are not appropriate for routine screening because of
their invasiveness, technical limitations, and cost.  Office
sphygmomanometry (the blood pressure cuff) remains the most appropriate
screening test for hypertension in the asymptomatic population.
Although this test is highly accurate when performed correctly, false-
positive and false-negative results (i.e., recording a blood pressure
that is not representative of the patient's average blood pressure) do
occur in clinical practice.[13] One study found that 21% of persons
diagnosed as mildly hypertensive based on office sphygmomanometry had no
evidence of hypertension when 24-hour ambulatory recordings were
obtained.[14]

Errors in measuring blood pressure may result from instrument, observer,
and/or patient factors.[15] Examples of instrument error include
manometer dysfunction, pressure leaks, stethoscope defects, and cuffs of
incorrect width or length for the patient's arm size.  The observer can
introduce errors due to sensory impairment (difficulty hearing Korotkoff
sounds or reading the manometer), inattention, inconsistency in
recording Korotkoff sounds (e.g., Phase IV vs.  Phase V), and
subconscious bias (e.g., "digit preference" for numbers ending with zero
or preconceived notions of "normal" pressures).  The patient can be the
source of misleading readings due to posture and biologic factors.
Posture (i.e., lying, standing, sitting) and arm position in relation to
the heart can affect results by as much as 10 mm Hg.[15] Biologic
factors include anxiety, meals, tobacco, alcohol, temperature changes,
exertion, and pain.  Due to these limitations in the test-retest
reliability of blood pressure measurement, it is commonly recommended
that hypertension be diagnosed only after more than one elevated reading
is obtained on each of three separate visits over a period of one to
several weeks.[1]

Additional factors affect accuracy when performing sphygmomanometry on
children; these difficulties are especially common when testing infants
and toddlers under 3 years of age.[16-18] First, there is increased
variation in arm circumference, requiring greater care in the selection
of cuff sizes.[19] Second, the examination is more frequently
complicated by the anxiety and restlessness of the patient.  Third, the
disappearance of Korotkoff sounds (Phase V) is often difficult to hear
in children and Phase IV values are often substituted.  Fourth,
erroneous Korotkoff sounds can be produced inadvertently by the pressure
of the stethoscope diaphragm against the antecubital fossa.  Finally,
the definition of pediatric hypertension has itself been uncertain
because of confusion over normal values during childhood.  The
definition of hypertension in childhood is essentially arbitrary, based
on age-specific percentile.[18] Age-, sex-, and height-specific blood
pressure nomograms for U.S.  children and adolescents have been
published more recently, based on data from 56,108 children aged 1-17
years.[20]

Self-measured (home) blood pressure and ambulatory blood pressure
monitoring may provide useful information in special circumstances
(e.g., research, persistent "white-coat" hypertension), but there is
insufficient evidence at present to warrant their routine use in
screening.[1,21-28]

Effectiveness of Early Detection

There is a direct relationship between the magnitude of blood pressure
elevation and the benefit of lowering pressure.  In persons with
malignant hypertension, the benefits of intervention are most dramatic;
treatment increases 5-year survival from near zero (data from historical
controls) to 75%.[29] Over the past 30 years, the results of many
randomized clinical trials of the effects of antihypertensive drug
therapy on morbidity and mortality in adult patients (>=21 years of
age) with less severe hypertension have been published.[30-32] The
efficacy of treating hypertension is clear, as demonstrated in a number
of older randomized controlled trials in adults with diastolic blood
pressures ranging from 90 to 129 mm Hg.[33-38] For example, in the
Veterans Administration Cooperative Study on Antihypertensive Agents,
middle-aged men with diastolic blood pressure averaging 90 through 114
mm Hg experienced a significant reduction in "morbid" events (e.g.,
cerebrovascular hemorrhage, congestive heart failure) after treatment
with antihypertensive medication.[34]

Persons with mild (Stage 1) to moderate (Stage 2)[1] diastolic
hypertension (90-109 mm Hg) also benefit from treatment.[30,39-41] This
was confirmed in the Hypertension Detection and Follow-Up Program, a
randomized controlled trial involving nearly 11,000 hypertensive men and
women, of whom 40% were black.[39] The intervention group received
standardized pharmacologic treatment ("stepped care") while the control
group was referred for community medical care.  There was a
statistically significant 17% reduction in 5-year all-cause mortality in
the group receiving standardized drug therapy; the subset with diastolic
blood pressure 90-104 mm Hg experienced a 20% reduction in
mortality.[39] Deaths due to cerebrovascular disease, ischemic heart
disease, and other causes were also significantly reduced in the stepped
care group.[42] Similar effects on all-cause mortality and
cardiovascular events have been reported in other randomized controlled
trials, such as the Australian National Blood Pressure Study (initial
diastolic blood pressure 95-109 mm Hg)[40] and the Medical Research
Council (MRC) trial (diastolic blood pressure 90-109 mm Hg).[41] In
these two trials, the relative reduction in rates of stroke or other
trial endpoints with treatment was similar in those with diastolic blood
pressures < 95 or 95-99 mm Hg and those with higher diastolic blood
pressures, although the absolute benefit was less due to smaller initial
risk of stroke and other diseases at lower blood pressures.  Both trials
included untreated control groups and did not report a significant
reduction in deaths from noncardiovascular causes in the actively
treated groups, confirming that the benefit was due to antihypertensive
treatment rather than to other medical care.

Earlier studies included some subjects over age 65 years, but in
insufficient numbers to permit firm conclusions.  Four large, randomized
placebo-controlled trials have since demonstrated conclusively the
benefit of antihypertensive treatment in elderly subjects (aged 60-97
years).[43-48] Three of these studies included persons with diastolic
blood pressures of 90-120 mm Hg, and among them reported significant
reductions in all-cause mortality,[46] cardiovascular mortality,[43,46]
cardiovascular events,[47] and strokes.[46,47] The Systolic Hypertension
in the Elderly Program (SHEP) trial included over 4,000 subjects >=60
years of age with isolated systolic hypertension (systolic blood
pressure >= 160 mm Hg, with diastolic blood pressure < 90 mm Hg),
and reported significant reductions in the incidence of stroke,
myocardial infarction, and left ventricular failure.[48] A meta-analysis
combining these and other trials that included persons aged >=60
years demonstrated that antihypertensive treatment in elderly persons
significantly reduced mortality from all causes (-12%), stroke (-36%),
and coronary heart disease (-25%), as well as stroke and coronary heart
disease morbidity.[49] This meta-analysis suggested reduced benefit with
increasing age, although differences were not statistically significant.
A second meta-analysis of randomized controlled trials in persons over
age 60 years concluded that absolute 5-year morbidity and mortality
benefits derived from trials were greater for older than for younger
subjects.[50] This meta-analysis calculated that 18 (95% CI, 14-25)
elderly hypertensive subjects needed to be treated for 5 years to
prevent one cardiovascular event.

Treatment of hypertension is associated with multiple benefits,
including reduced coronary heart disease and vascular deaths, but meta-
analyses suggest it produces the largest reductions in cerebrovascular
morbidity and mortality.[30-32,49,50] Improved treatment of high blood
pressure has been credited with a substantial portion of the greater
than 50% reduction in age-adjusted stroke mortality that has been
observed since 1972.[1,51,52]

Although the efficacy of antihypertensive treatment for essential (also
called primary) hypertension has been well established in clinical
research, certain factors may influence the magnitude of benefit from
hypertension screening achieved in actual practice.  Compliance with
drug therapy may be limited by the inconvenience, side effects, and cost
of these agents.[53,54] Serious or life-threatening drug reactions in
the clinical trials were rare, but less serious side effects were
common, resulting in discontinuation of randomized treatment (almost 20%
by the fifth year in the MRC trial,[41] for example) or a substantial
increase in patient discomfort.[34] Higher incidences of mild
hypokalemia, hyperuricemia, and elevated fasting blood sugar have also
been reported in treated individuals.[35] A population-based case-
control study suggested an increased risk of primary cardiac arrest with
certain diuretic regimens (e.g., higher doses, use without potassium-
sparing therapy).[55] However, current drug regimens, including low-dose
diuretics, are associated with fewer adverse effects and with favorable
effects on quality of life.[55a] Newer classes of drugs (e.g., calcium
channel blockers, angiotensin-converting enzyme inhibitors) have not
been assessed in long-term trials with clinical endpoints.  Their
effects on cardiovascular morbidity and mortality may differ from the
effects reported in the clinical trials cited above, which used
diuretics or beta-blockers.

Whether hypertension screening is equally effective for other
populations or with treatments other than drugs is less clear.  The
benefits of hypertension treatment are less well studied in certain
population groups, such as children (see below), Native Americans,
Asians and Pacific Islanders, and Hispanics.  The effects of
nonpharmacologic first-line therapy (i.e., weight reduction in
overweight patients, increased physical activity, sodium restriction,
and decreased alcohol intake) on cardiovascular morbidity and mortality
are unstudied.  Although these nonpharmacologic therapies can sometimes
lower blood pressure in the short term,[1,56-62a] the magnitude of blood
pressure reduction achieved is generally smaller than that achieved with
drug therapy, and both the magnitude and duration of reduction in actual
practice may be limited by biologic factors (e.g., varying
responsiveness to sodium restriction) and the difficulties of
maintaining behavioral changes (e.g., weight loss).  Some of these
interventions, such as sodium restriction, may also have adverse effects
on quality of life.[63]

The detection of high blood pressure during childhood is of potential
value in identifying those children who are at increased risk of primary
hypertension as adults and who might benefit from earlier intervention
and follow-up.  Hypertensive vascular and end-organ damage may begin in
childhood,[64-69] although it is unclear how strongly these
pathophysiologic changes are associated with subsequent cardiovascular
disease.  Prospective cohort studies have shown that children with high
blood pressure are more likely than other children to have hypertension
as adults.[70-78] Correlation coefficients from these studies were
generally less than 0.5, however, suggesting a limited role for high
blood pressure in childhood as a predictor of adult hypertension.
Although controlled trials in children show that short-term (up to 3
years) effects on blood pressure can be achieved with changes in diet
and activity,[79-82] studies demonstrating long-term changes in blood
pressure are lacking.  There are no trials showing that lowering blood
pressure in childhood results in reduced blood pressure in adulthood.  A
relationship between lowering blood pressure during childhood and
improved morbidity and mortality in later life is unlikely to be
demonstrated, given the difficulty of performing such studies.

A relatively high proportion of children with hypertension have
secondary, potentially curable forms.  Among children and adolescents
whose hypertension was evaluated in primary care centers, an estimated
28% had secondary hypertension (e.g., renal parenchymal disease,
coarctation of the aorta).[69] This contrasts with hypertensive adults
seen in primary care settings, of whom only 7% are estimated to have
secondary hypertension.[83] Screening children and adolescents may be
justifiable if the morbidity of these conditions is improved by early
detection and treatment.  Many causes of secondary hypertension in
childhood are detectable by careful history-taking (e.g., preterm birth,
umbilical artery catheter, chronic pyelonephritis, renal disease,
bronchopulmonary dysplasia; symptoms of cardiac, renal, endocrinologic,
or neurologic disease) or physical examination (e.g., murmur, decreased
femoral pulses, abdominal bruit).[69,84] Characteristic symptoms and
signs, such as those of aortic coarctation, are often overlooked,
however.[85-87] Numerous surgical case series suggest that delay in
surgical repair of aortic coarctation increases the likelihood of
irreversible hypertension,[88-94] although none of these series
controlled for other differences between persons presenting early versus
late in life.  Uncontrolled studies indicate that some important causes
of hypertension for which definitive cures are available, including
coarctation and renovascular disease, may not be diagnosed until
complications such as congestive heart failure, aortic rupture, or
stroke occur.[6-9] Prognosis with early surgical intervention is
improved compared with historical controls.[88,95]

Recommendations of Other Groups

Recommendations for adults have been issued by the Joint National
Committee on Detection, Evaluation, and Treatment of High Blood
Pressure,[1] and similar recommendations have been issued by the
American Heart Association.[96] These call for routine blood pressure
measurement at least once every 2 years for adults with a diastolic
blood pressure below 85 mm Hg and a systolic pressure below 130 mm Hg.
Measurements are recommended annually for persons with a diastolic blood
pressure of 85-89 mm Hg or systolic blood pressure of 130-139 mm Hg.
Persons with higher blood pressures require more frequent measurements.
The American College of Physicians (ACP)[97] and the American Academy of
Family Physicians (AAFP)[98] recommend that all adults 18 years and
older be screened for hypertension every 1-2 years.  The AAFP policy is
currently under review.  The ACP also recommends screening at every
physician visit for other reasons, and that those in high-risk groups
(e.g., diastolic 85-89 mm Hg, previous history of hypertension) be
screened on an annual basis.  The Canadian Task Force on the Periodic
Health Examination recommends that all persons aged 21 years and over
receive a blood pressure measurement during any visit to a physician
("case finding").[99]

The American Academy of Pediatrics (AAP),[100] the National Heart, Lung,
and Blood Institute,[18] the AAFP,[98] Bright Futures,[101] the American
Medical Association,[102] and the American Heart Association[103]
recommend that children and adolescents receive blood pressure
measurements every 1 or 2 years during regular office visits.  The
Canadian Task Force found insufficient evidence to recommend for or
against routine blood pressure measurement in persons under age 21
years.[99] The AAP recommends against universal neonatal blood pressure
screening.[104]

Discussion

It is clear from several large randomized clinical trials that lowering
blood pressure in hypertensive adults is beneficial and that death from
several common diseases can be reduced through the detection and
treatment of high blood pressure.  Estimates suggest that an average
diastolic blood pressure reduction of 5-6 mm Hg in everyone with
hypertension could reduce the incidence of coronary heart disease by 14%
and the incidence of strokes by 42%.[30,31] At the same time, it is
important for clinicians to minimize the potential harmful effects of
detection and treatment.  For example, if performed incorrectly,
sphygmomanometry can produce misleading results.  Some hypertensive
patients thereby escape detection (false negatives) and some
normotensive persons receive inappropriate labeling (false positives),
which may have certain psychological, behavioral, and even financial
consequences.[105] Treatment of hypertension can also be harmful as a
result of medical complications, especially related to drugs.
Clinicians can minimize these effects by using proper technique when
performing sphygmomanometry, making appropriate use of nonpharmacologic
methods, and prescribing antihypertensive drugs with careful adherence
to published guidelines.[1,106-108]

The diastolic blood pressure above which therapy has been proven
effective (i.e., diastolic blood pressure > 90 mm Hg) is to a large
extent based on the artificial cutpoints chosen for study purposes
rather than on a specific biologic cutpoint defining increased risk.
The coronary heart disease mortality risk associated with blood pressure
occurs on a continuum that extends well below the arbitrarily defined
level for abnormal blood pressure, beginning for systolic blood pressure
above 110 mm Hg and for diastolic pressure above 70 mm Hg.[5]
Nevertheless, many organizations outside the U.S.  have been reluctant
to recommend drug therapy for persons with diastolic blood pressures
below 100 mm Hg who lack additional risk factors.[106,108-111] Drug
treatment of mild hypertension is of particular concern for young
adults: the evidence for therapeutic benefit comes primarily from
several older trials[34,36,38] that included only a few individuals in
their 20s, the potential adverse effects of decades of antihypertensive
therapy are undefined, and the absolute benefits in young adults are
likely to be limited given their small risk of stroke and coronary heart
disease.  For persons with mild hypertension, most recommendations
suggest including age and/or the presence of other cardiovascular
disease risk factors or concomitant diseases (e.g., smoking, obesity,
renal disease, peripheral vascular disease) to modify treatment
decisions.[1,106,108-111]

Tracking studies and pathophysiologic evidence suggest there may be some
benefit from early detection of primary hypertension in childhood, but
there is insufficient evidence to support routine screening solely for
this purpose.  The lack of evidence is of concern because it is unclear
whether a policy of routinely screening all children and adolescents to
detect primary hypertension would achieve sufficient clinical benefit
later in life to justify the costs and potential adverse effects of
widespread testing and treatment.  Potentially curable causes of
hypertension, which account for a relatively large proportion of cases
in young children, are often overlooked on history and physical
examination, with rare but potentially catastrophic consequences.
Evidence from case series and multiple time series indicate that early
detection of secondary hypertension in childhood is of substantial
benefit to the small number of patients affected.

CLINICAL INTERVENTION

Periodic screening for hypertension is recommended for all persons
>=21 years of age ("A" recommendation).  The optimal interval for
blood pressure screening has not been determined and is left to clinical
discretion.  Current expert opinion is that adults who are believed to
be normotensive should receive blood pressure measurements at least once
every 2 years if their last diastolic and systolic blood pressure
readings were below 85 and 140 mm Hg, respectively, and annually if the
last diastolic blood pressure was 85-89 mm Hg.[1] Sphygmomanometry
should be performed in accordance with recommended technique.[1]
Hypertension should not be diagnosed on the basis of a single
measurement; elevated readings should be confirmed on more than one
reading at each of three separate visits.  In adults, current blood
pressure criteria for the diagnosis of hypertension are an average
diastolic pressure of 90 mm Hg or greater and/or an average systolic
pressure of 140 mm Hg or greater.[1] Once confirmed, patients should
receive appropriate counseling regarding physical activity (Chapter 55),
weight reduction and dietary sodium intake (Chapter 56), and alcohol
consumption (Chapter 52).  Evidence should also be sought for other
cardiovascular risk factors, such as elevated serum cholesterol (Chapter
2) and smoking (Chapter 54), and appropriate intervention should be
offered when indicated.  The decision to begin drug therapy may include
consideration of the level of blood pressure elevation, age, and the
presence of other cardiovascular disease risk factors (e.g., tobacco
use, hypercholesterolemia), concomitant disease (e.g., diabetes,
obesity, peripheral vascular disease), or target-organ damage (e.g.,
left ventricular hypertrophy, elevated creatinine).[1,106,108]
Antihypertensive drugs should be prescribed in accordance with recent
guidelines[1,106,108] and with attention to current techniques for
improving compliance.[53,54]

Measurement of blood pressure during office visits is also recommended
for children and adolescents ("B" recommendation).  This recommendation
is based on the proven benefits from the early detection of treatable
causes of secondary hypertension; there is insufficient evidence to
recommend for or against routine periodic blood pressure measurement to
detect essential (primary) hypertension in this age group.
Sphygmomanometry should be performed in accordance with the recommended
technique for children, and hypertension should only be diagnosed on the
basis of readings at each of three separate visits.[18] In children,
criteria defining hypertension vary with age.[18] Age-, sex-, and
height-specific blood pressure nomograms for U.S.  children and
adolescents have been published.[20]

Routine counseling to promote physical activity (Chapter 55) and a
healthy diet (Chapter 56) for the primary prevention of hypertension is
recommended for all children and adults.

The draft update of this chapter was prepared for the U.S.  Preventive
Services Task Force by Carolyn DiGuiseppi, MD, MPH, based in part on
material prepared for the Canadian Task Force on the Periodic Health
Examination by Alexander G.  Logan, MD, FRCPC, and Christopher
Patterson, MD, FRCPC.

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