An Evaluation of the Vita-Stat Automatic
Blood Pressure Measuring Device
B. FRANK POLK, M.D.,
M. S c ,
BERNARD ROSNER, P H . D . ,
R U D Y FEUDO, M. E D . , AND MARTIN VANDENBURGH,
B.A.
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SUMMARY Four Vita-Stat (VS) automatic, coin-operated, blood pressure measuring derices were
evaluated for accuracy and precision. Under field conditions, 342 adults had two blood pressure measurements
with both the VS device and with the Random-Zero (RZ) device. Two of the VS machines gave significantly
higher systolic (SBP) and diastolic blood pressure (DBP) values, compared to the RZ values. The mean
difference between these two units and the RZ device were clinically important (14.0 and 6.9 mm Hg SBP; 7.5
and 6.8 mm Hg DBP), and resulted hi the misclassiflcation of 23% of normotensives as hypertensives. We
observed a significant order effect on SBP with the VS device, with a mean decrement of 4.9 mm Hg between
the first and second SBP values, compared to 0.6 mm Hg with the RZ device. Even after adjusting for this bias,
all four VS devices gave significantly more variable SBP readings than the RZ unit; two of the four also gave
more variable DBP values. These data suggest that the VS device is neither accurate nor precise enough at the
present time to be recommended for widespread use. These findings also raise questions concerning the
monitoring of performance of this and similar devices in the field. (Hypertension 2: 221-227, 1980)
KEYWORDS
• blood pressure measuring device
• Vita-Stat device
R
• Random-Zero device
our knowledge.1 We have evaluated four of these
machines, under field conditions, for accuracy and
precision.
ELIABLE automatic blood pressure measuring devices may have an important role in
the detection of elevated blood pressure and
perhaps in improving compliance with therapy among
individuals with known hypertension. Recently, a
coin-operated device called the Vita-Stat Computer
(Vita-Stat Medical Services, Tierra Verde, Florida)
has been distributed to many pharmacies, department
stores, banks, shopping centers, and hotels across the
United States. This device is fully automatic and uses
the standard auscultation (Korotkoff sound) principle
of measurement. Despite the claim of the company
that "Independent research studies by leading medical
authorities have proven the accuracy of the Vita-Stat
computer," only one such study has been published, to
Patients and Methods
During December, 1978, adult customers (ages 20
and over) in one pharmacy, one department store, and
two shopping centers were invited to have their blood
pressures measured. A list of 61 locations in northern
New England was provided by the company, which
was not aware of the evaluation program. These four
locations were chosen from the list because they were
in the greater Boston area, and because it was estimated that their customers would be reasonably
representative of the general adult population of New
England, and would be sufficiently numerous so that
approximately 100 persons could be screened at each
site in a short period of time.
The Vita-Stat device (VS) measures systolic and
diastolic blood pressures and is based on the auscultation principle. The customer places his left arm in a
From the Channing Laboratory and Departments of Medicine
and Social and Preventive Medicine, Harvard Medical School; and
the Peter Bent Brigham Hospital Division of the Affiliated
Hospitals Center, Inc., Boston, Massachusetts.
Address for reprints: B. Frank Polk, M.D., Channing
Laboratory, 180 Longwood Avenue, Boston, Massachusetts 02115.
Received August 9, 1979; revision accepted October 30, 1979.
221
222
HYPERTENSION
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looped cuff so that when the cuff closes automatically
it will be placed starting at the elbow. A microphone is
mounted in the cuff such that it is near the brachial
artery when the arm is inserted. When the start button
is pressed, the cuff tightens snugly by use of a slip
clutch and inflates to 160 mm Hg. If Korotkoff sounds
are sensed at that pressure, inflation continues in 20
mm Hg increments until Korotkoff sounds are no
longer sensed or a maximum pressure of 220 mm Hg
is reached. The cuff then deflates in 4-6 mm Hg
decrements with a brief pause after each decrement to
determine the presence or absence of Korotkoff
sounds. Systolic blood pressure (SBP) is registered at
the appearance of Korotkoff sounds and diastolic
blood pressure (DBP) at their disappearance. There is
an artifact rejection system built into the machine so
that extraneous noise and false sounds are filtered out
or rejected.
The blood pressure values recorded by VS were
compared to those obtained by a trained observer
using the modified Random-Zero device (RZ)
(Hawksley, Sussex, England). This device is similar in
principle to the standard mercury sphygmomanometer. A mechanical device interposed between the mercury reservoir and manometer column, however,
draws variable amounts of mercury into an expandable chamber. This modification has the effect of
obscuring the true zero level of mercury until the end
of the reading, thus minimizing observer bias.1
Labarthe et al.' have shown good agreement between
overall mean SBP and DBP as determined by the RZ
device compared to a standard mercury sphygmomanometer (Baumanometer 300), although RZ
values tended to be slightly lower.
All data were collected by one screener who had extensive training and experience in blood pressure
screening programs. Training and standardization included orientation to physiologic aspects of systemic
arterial blood pressure, to the techniques of its indirect
measurement, and to familiarization with the
modified RZ. This screener was trained and tested by
performing multiple readings with a double
stethoscope on several subjects, and was standardized
by a technique based on audio cassette tapes described
by Rose.4
A brief questionnaire was administered before the
blood pressures were obtained. Data collected included age, sex, race, history of hypertension, and
antihypertensive treatment.
When the participant was sitting, four blood
pressure measurements on the left arm were taken:
two with the VS and two with the RZ. For the RZ
measurements, the appropriate cuff size was chosen on
the basis of arm circumference. The devices were used
in an alternating sequence, and the order of the sequence (VS-VS-RZ-RZ vs RZ-RZ-VS-VS) was determined by using a table of random numbers. The 50
cents required for each VS measurement was supplied
by the investigators. The RZ device was calibrated
between sites.
A paired t test was used to compare mean blood
pressures obtained with the VS and RZ machines.'
VOL 2, No 2, MARCH-APRIL
1980
This method also was used to compare the order effect
(first reading minus second reading) for the two
devices. The measure of variability chosen was the
mean absolute difference between replicates after correcting for the above order effect = 8x (5y) = | XH —
X21 - Ax | ( | Yu - Y2I - Ay | ), where X,,, X21
and Y u , Y21 are the first and second readings for the
VS and RZ devices respectively, and Ax (Ay) = %n XJI (Yn — Y21). For each location, Ax and Ay were
computed separately. A paired t test was then used to
compare 8\ and 5y based on the statistic 8x— 8y
= I X,, - X21 - Ax | - | Y,, - YM - Ay | .
Results
Patient Characteristics
A total of 412 individuals were interviewed: 106,
101, 105, and 100 from locations A-D respectively.
Individuals were excluded from analysis if they were
missing one or more systolic or diastolic readings on
either machine. There were no missing RZ readings,
but 70 persons (17.0%) were excluded from analysis
because of missing VS readings (8, 17, 7, and 38
respectively). In each instance of missing values, the
VS read out blank readings and returned the coins. A
third measurement was not attempted in these cases.
Characteristics of the 342 persons for whom blood
pressure data were complete are presented in table 1.
The study population was predominantly white
(92.4%), had a median age of 57 years, and was approximately half men and half women. Of interest,
nearly half (47.4%) had been told in the past by a
physician that their blood pressures were elevated,
over one-third (36.4%) had at one time been treated
for hypertension, and 29.0% were taking antihypertensive medication(s) at the time of screening.
Accuracy
The mean systolic and diastolic blood pressures are
presented by location in table 2. At two locations there
were negligible, nonsignificant differences between VS
and RZ blood pressure readings. Two of the VS
machines, however, gave notably higher mean SBP
(14.0 and 6.9 mm Hg) and DBP (7.6 and 6.8 mm Hg)
measurements compared to those obtained with the
RZ. For these two units, the differences were significant, with p values < 0.001. The frequency distributions of these differences are given in table 3. At
locations C and D, the mean of two systolic readings
with the VS was > 20 mm Hg higher than the RZ in
28.6% and 9.7% of participants respectively; the mean
of two diastolic readings with the VS was > 10 mm
Hg higher than the RZ in 40.8% and 37.1% of participants respectively.
The potential effects on sensitivity and specificity if
the VS readings were used to diagnose high blood
presure are shown in table 4. We assumed that the
"correct" diagnosis is given by the RZ and that high
blood pressure is defined (arbitrarily) as SBP 160 mm
Hg and/or DBP 95 mm Hg, because these are the
AUTOMATIC BLOOD PRESSURE MEASUREMENT/Po/fc and Rosner
223
TABLE 1. Characteristics of S4£ Participants: Age, Sex, Race, and Hypertension Status
n
%
20-29
30-39
40^9
50-59
60-69
70-79
80-89
39
39
54
66
100
38
6
11.4
11.4
15.8
19.3
29.2
11.1
1.8
Sex distribution
(n = 342)
Men
Women
164
178
48.0
52.0
Race distribution
(n = 342)
White
Black
Other
316
23
3
92.4
6.7
0.9
History of hypertension
(n - 340)
Yee
No
161
179
47.4
52.6
Previously taken antihypertensive Yes
medication (n = 338)
io
123
215
36.4
63.6
Currently taking antihypertensive Yes
medication (n = 338)
io
98
240
29.0
71.0
Characteristic
Age distribution
(n = 342)
Overall
- 53.0
«= 16.1
median = 57
range = 20-89
X
8D
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TABLE 2. Mean Blood Pressures and Differences Between Vita-Stat and Random-Zero Device Readings at
Four Different Locations
Location
Random-Zero
Vita-Stat
Difference*
t statistic
p value
Systolic blood pressure (mm Hg)
n
A
B
C
D
98
84
98
62
X
142.5
134.1
147.9
135.4
SD
X
8D
S
8D
21.0
22.5
20.3
16.7
142.0
133.6
133.9
128.5
18.1
23.2
18.3
19.0
0.5
0.5
14.0
6.9
11.2
12.1
11.7
13.6
0.475
0.405
11.909
3.982
n.s.
n.s.
< 0.001
< 0.001
8D
t statistic
-0.650
0
7.871
5.825
p value
n.s.
n.s.
< 0.001
< 0.001
Diastolic blood pressure (mm Hg)
n
S
A
98
B
C
D
84
83.9
79.7
89.0
87.3
98
62
SD
12.6
13.1
12.0
13.3
i
85.2
79.7
81.4
80.4
8D
if
11.3
12.0
9.9
10.9
-1.3
0.0
7.6
6.8
6.4
8.6
9.5
9.2
*A paired means t test was used to analyze differences between the means of two machines.
cutoff points chosen for the definition of definite
hypertension by the U. S. Public Health Service" as
well as by the distributors of the VS. Overall, 23.3% of
the normotensive participants were incorrectly
classified as hypertensive, and 16.4% of the hypertensive participants were incorrectly classified as normotensive.
Precision
As shown in table 5, we observed a significant and
noteworthy order effect on SBP values with the VS.
That is, there was a significant decrement between the
first and second VS SBP readings (mean difference =
4.88 mm Hg;/? < 0.001) compared to a small and nonsignificant decrement between the first and second RZ
SBP readings (mean difference = 0.58 mm Hg; p =
not significant). The difference in order effect between
the VS and RZ was about twice as great when the VS
recordings are first and second (overall mean
difference = 5.72 mm Hg) as compared to when the
RZ recordings are first and second (overall mean
difference = 2.83 mm Hg). The order effect on systolic
readings, however, is significantly larger for VS in
HYPERTENSION
224
VOL 2, No 2, MARCH-APRIL 1980
TABLE 3. Frequency Distribution of Differences Between Mean Values of the VitaStat Replicates and RandomZero Replicates
Mean of 2 VS readings
minus mean of 2 RZ
readings*
B
A
n
n
%
D
C
n
%
%
n
%
2
3.2
Systolic blood pressure (mm Hg)
<-20
>-20, < - 1 0
>-10, <
0
>
0, < 10
> 10, < 20
3
3.1
4
4.8
1
1.0
14
14.3
28.6
36.7
15.3
15
0
0.0
3
4.8
4
4.1
9
33
22
14.5
32.3
35.5
4
4.8
33.7
32.7
28.6
20
10
17.9
25.0
35.7
11.9
6
9.7
28
36
15
2
>20
21
30
2.0
98
32
28
84
98
62
Diastolic blood pressure (mm Hg)
I
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>-15,
>-10,
> - 5,
>
0,
>
5,
> 10,
<-10
<- 5
0
<
5
<
< 10
< 15
2
2.0
3
3.6
3
3.0
1
1.6
6
6.1
7
8.3
2
2.0
1
1.6
19
13
4.1
4
6.5
6
6.1
8.
22
13
15.5
16.7
28.6
15.5
4
10
19.4
31.6
24.5
10.2
6
6.1
8
9.5
20
0
0.0
2
2.4
20
22.4
21.4
20.4
20.4
12.9
19.4
21.0
21.0
16.1
31
24
>15
14
24
21
84
98
12
13
13
10
98
62
•VS = Vita-Stat device; RZ = Random-Zero device.
TABLE 4. Sensitivity and Specificity of Diagnosis of Hypertension Made by the Vita-Stat Device, Using Criteria of Mean SBP
> 160 mm Hg and/or DBP > 95 mm Hg
Mean RZ
<160
— (RZ normotensive)
Mean RZ ^ , . and/or (RZ hypertensive)
•^ y o
Location
A
B
C
D
All
Mean VS _ „_ Mean VS n r , and/or n Specificity
< 95
95+
60
10
70
85.7
62
67
92.5
5
60.2
83
50
33
39
16
55
70.9
211
64
275
76.7
160+
160+
Mean VS < 95
nr. Mean VS „?
95+, and/or n Sensitivity
5
23
28
82.1
4
13
17
76.5
93.3
1
14
15
1
85.7
6
7
11
56
67
83.6
Abbreviations: SBP = systolic blood pressure; DBP =• diastolic blood pressure; RZ = Random-Zero device; VS = Vita-Stat
device.
both instances. The sequence of recordings began with
the VS in 52% of participants. There was not an important order effect on DBP measurements with either
device.
Finally, the variability of each VS machine is compared to the RZ in table 6. At all 4 locations, SBP
measurements on the VS were significantly more
variable than the RZ counterparts. Two of the VS
machines also gave significantly more variable DBP
measurements compared to the RZ.
Discussion
Accuracy
As one very important performance characteristic
of automatic blood pressure measuring devices,
AUTOMATIC BLOOD PRESSURE MEASUREMENT/Po/Jt and Rosner
225
TABLE 5. Comparison of Difference Between First and Second Blood Pressure Readings with VitaStat and Random-Zero Devices
Diastolic blood pressure
I statistic p value
SD
Systolic blood pressure
t statistic p value
SD
Location
n
X
A
B
C
D
98
4.50
4.49
5.97
4.27
4.88
10.38
12.07
12.34
11.09
11.53
1.20
0.00
0.57
0.39
0.58
8.04
7.33
8.02
7.05
7.70
1.48
0.00
0.70
0.44
1.39
3.30
4.49
5.40
3.89
4.30
12.77
15.06
15.30
13.33
14.22
2.56
2.73
3.49
2.30
5.59
Vita-Stat
All
84
98
62
342
4.29
3.41
4.79
3.03
7.83
0.59
0.38
1.77
1.16
0.98
5.28
6.48
8.89
11.38
8.05
1.11
0.54
1.97
0.80
2.25
0.65
-0.10
0.29
0.36
0.31
4.47
4.83
4.31
5.13
4.65
1.44
-0.19
0.67
0.55
1.19
n.s.
n.s.
n.s.
n.s.
n.s.
7.15
8.10
9.66
12.74
9.34
-0.08
0.54
1.52
0.50
1.33
n.s.
n.s.
n.s.
n.s.
n.s.
< 0.001
0.001
< 0.001
0.004
< 0.001
n.s.
n.s.
n.s.
n.s.
0.024
Random-Zero
A
B
C
D
All
98
84
98
62
342
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A
98
B
C
D
84
98
All
342
62
n.s.
n.s.
n.s.
n.s.
n.s.
Vita-Stat—Random-Zero
-0.06
0.012
0.48
0.008
1.48
< 0.001
0.81
0.025
0.67
< 0.001
TABLE 6. Variability of SBP and DBP Measurements of the Vita-Stat Machine Compared to the RandomZero Device (A = VS-RZ)
Location
Mean A
A
2.33
2.51
2.55
2.65
Systolic blood pressure (mm Hg)
7.97
98
10.06
84
9.44
98
8.19
62
2.89
2.29
2.67
2.55
0.29
0.81
3.05
4.83
Diastolic blood pressure (mm Hg)
4.20
98
84
5.53
6.77
98
62
8.89
0.68
1.34
4.46
4.28
B
C
D
A
B
C
D
SD
measurements of SBP and DBP should closely approximate readings obtained by adequately trained
observers using mercury sphygmomanometers. 8 ' 7
Evaluation of accuracy should be performed under
field conditions and on multiple units of the device.
Two of the four automatic units evaluated in this
study produced mean SBP and DBP readings that
were significantly and importantly higher than paired
n
t statistic
p value
0.005
0.025
0.009
0.013
TIM.
n.s.
< 0.001
< 0.001
measurements obtained with the RZ. These mean
differences did not result from a few extreme discrepancies; these two devices yielded a mean SBP or
DBP that was > 10 mm Hg higher in approximately
60% and 40% respectively of the paired comparisons.
It is unlikely that the discrepancies resulted from
systematically lower measurements determined by the
trained observer, since the RZ minimizes observer
226
HYPERTENSION
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bias,2 and since there was close agreement between the
RZ and VS in two locations. Inadequate maintenance
may have contributed to the inaccuracies observed,
but one of the faulty VS was serviced unexpectedly in
the middle of the evaluation process, and it was
observed that the subsequent VS readings remained
generally higher than the paired readings.
The number of VS devices (four) evaluated in this
study was small. The locations were not chosen randomly, but rather on the basis of convenience and estimated representativeness of their customer populations. Thus, it is possible that our findings are not
representative. However, they are comparable to
those of Berkson et al.1 who compared blood pressure
values determined by eight randomly chosen VS
machines with those obtained by two trained
screeners. The number of participants (10-34) at each
site was small, but three of the eight machines gave
significantly higher systolic readings than those of the
screeners, and two gave significantly higher diastolic
readings. They observed that the average machinehuman difference in SBP varied from -5.7 to 12 mm
Hg, and concluded that the VS SBP determinations
" . . . may be unduly sensitive to malfunction or maladjustment . . . " These investigators also found that
machine-human agreement on blood pressure
classification was somewhat lower than the humanhuman agreement.
We compared the VS to one highly trained screener.
It would be of great interest to compare the interobserver variability between two human observers —
with and without special training — to the variability
between two VS machines.
Precision
There was a striking order effect in SBP measurements with all four VS devices; that is, the first VS
SBP reading was significantly and notably higher than
the second (approximately 5 mm Hg higher, on average) on all four machines. This was especially true if
the first measurement in the sequence of four was obtained on the VS device. In contrast, there were small
and generally nonsignificant order effects with the RZ
SBP readings, and with either device with regard to
DBP readings. Order effects in this direction have
been reported previously*' * and are assumed to be due
to adaptation. The notably greater order effect on
SBP here observed with the VS device may be related
to greater apprehension experienced while placing
one's arm into an entrapping machine than that experienced with the cuff of a sphygmomanometer that
allows mobility. While it was not done in this study,
future evaluations should record whether or not participants have used the device previously. It should be
remembered that this order effect occurred while a
screener was present; it is at least possible that blood
pressures might be even more elevated when the
average person engages the machine alone. The importance of this phenomenon increases when one
realizes that most individuals are not likely to buy two
VOL 2, No
2, MARCH-APRIL
1980
consecutive measurements within a short time and, indeed, are not advised to do so by the literature found
on the machine. The major consequence of this order
effect is on false positive misclassification. Our estimate of 23.3% of normotensives misclassified as
hypertensive was based on the mean of two VS
measurements, and thus are conservative.
Even after accounting for this order effect, the
variability of SBP values in the VS readings was consistently and significantly greater than the variability
in the RZ measurements. As shown in table 6, the absolute differences in mean replicate BP readings after
subtracting the bias (order effect) from the VS and RZ
values are significantly greater for all four VS
machines than their RZ counterparts with respect to
SBP and for two machines with respect to DBP.
Implications
The consequences of spuriously elevated blood
pressure measurements depend on the actions taken
by the individuals in question. If measurements are
made for screening purposes, i.e., evaluation of persons with unknown blood pressure status, then misclassification as hypertensive may result in unwarranted anxiety in individuals without sustained
elevations in blood pressure, and misclassification as
normotensive may cause a false sense of security and
delay accurate diagnosis and proper treatment. While
a false positive misclassification of hypertension may
be preferable to a false negative misclassification, it
clearly is better to minimize all classification errors.
Over-diagnosis is not only likely to cause apprehension, but is likely to result in unnecessary visits to
physician's offices for confirmation or, more likely,
refutation of the diagnosis of hypertension. Although
the data are sparse and conflicting, there have been
suggestions that labelling persons as hypertensive may
have adverse psychological and behavioral consequences.10 These consequences presumably are not
dependent on accurate diagnosis but simply on the
label itself.
If measurements are made for the evaluation of
blood pressure status in persons known to be
hypertensive, then the result is misassessment of blood
pressure control. Despite instructions that accompany
the machine, some individuals may decide to change
their antihypertensive medications on their own initiative, with the possibility of adverse consequences.
At best, spuriously high readings are likely to cause
undue anxiety and unnecessary visits to the physician.
Ironically, this automatic blood pressure measuring
device may be cost-ineffective by increasing the
number of physician visits.
There is, perhaps, a more important question raised
by these data: who is responsible for monitoring the
performance of these commercial machines with
respect to validity and repeatability? How and how
often is performance to be monitored? The data
presented here suggest that the maintenance and/or
calibration provided by the distributor are inadequate.
AUTOMATIC BLOOD PRESSURE MEASUREMENT/i»o/Jt and Rosner
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If performance has to be monitored closely by
regulatory governmental agencies, the devices may
not be cost-effective, even if accurate. Our observation
that two of four machines tested in the field were inaccurate implies that all machines would have to be
monitored carefully and continuously. A possible
alternative would be to restrict distribution of devices
to a few locations where they could be carefully and
efficiently monitored.
The economics of visits to the physician for blood
pressure determinations make a fully automatic blood
pressure measuring machine highly attractive. Such a
device could have an important role in the detection
and management of high blood pressure, and might
improve compliance with therapy among some individuals just as self-recording of blood pressures has
been shown to do. In evaluating the effect of selfrecording of blood pressure, Johnson et al. 11
demonstrated a reduction in blood pressure among
hypertensive patients who admitted to difficulty
remembering to take their pills.
We agree with a recent editorial in Lancet12 that
these devices are to be encouraged " . . . provided that
the measurement is reasonably accurate, that the instructions given are sensible, and that doctors
cooperate by checking the blood pressure themselves
. . . " The data presented here, however, suggest that
the Vita-Stat device currently is not "reasonably" accurate, and its use is not to be encouraged at this time.
There is a need for further evaluation of more
specimens of this device.
227
References
1. Berkson DM, Whipple IT, Shireman L, Brown MC, Raynor
W, Shekelle RB: Evaluation of an automated blood pressure
measuring device intended for general public use. Am J Public
Health 69: 473, 1979
2. Wright BM, Dore CF: A random-zero sphygmomanometer.
Lancet 1: 337, 1970
3. LaBarthe DR, Hawkins CM, Remington, RD: Evaluation of
performance of selected devices for measuring blood pressure.
Am J Cardiol 32: 546, 1973
4. Rose GA: Standardization of observers in blood pressure
measurement. Lancet 1: 673, 1965
5. Snedecor G, Cochran WG: Statistical Methods, 6th ed. Ames,
Iowa, Iowa State University Press, 1967, p 93
6. U.S. Department of Health, Education and Welfare. PHS. Advance Data from Vital and Health Statistics. No. 1,
Washington, D.C., U.S. Government Printing Office, October,
1976
7. Feinlieb M, LaBarthe D, Shekelle R, Kuller, L: Criteria for
evaluation of automated blood pressure measuring devices for
use in hypertensive screening programs. Circulation 49:6, 1974
8. Wilber JA, Millward D, Baldwin A, Capron B, Silverman D,
James LM, Wolbert T, McCombs NJ: Atlanta community high
blood pressure program methods of community hypertension
screening. Circ Res 30 (suppl II): 11-101, 1972
9. Hypertension Detection and Follow-Up Program Cooperative
Group: Variability of blood pressure and the results of screening in the Hypertension Detection and Follow-Up Program. J
Chronic Dis 3 1 : 651, 1978
10. Haynes RB, Sackett DL, Taylor DW, Gibson ES, Johnson AL:
Increased absenteeism from work after detection and labeling
of hypertensive patients. N Engl J Med 299: 741, 1978
11. Johnson AL, Taylor DW, Sackett DL, Dunnett CW, Shimizu
AG: Self-recording of blood pressure in the management of
hypertension. Can Med Assoc J 119: 1034, 1978
12. Editorial: Who should measure the blood pressure? Lancet 1:
137, 1979
An evaluation of the Vita-Stat automatic blood pressure measuring device.
B F Polk, B Rosner, R Feudo and M Vandenburgh
Hypertension. 1980;2:221-227
doi: 10.1161/01.HYP.2.2.221
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