CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 2, March 2012
88
AFRICA
The lower frequency of zero EDP in the BP readings by consult-
ants was not unexpected, taking into consideration their years
of training and practice, and the fact they are more likely to be
conversant with guidelines for BP measurement.
The senior residents showed a higher frequency for zero
EDP than the junior residents, a finding which was unexpected,
considering the senior residents’ knowledge base and years of
training. However, many publications have pointed out the lack
of formal training and assessment in BP measurement during
undergraduate and postgraduate medical training, and this could
have been responsible for our findings.
9,19,24-26
In fact, Gonzalez-
Lopez
et al.
24
pointed out that inadequate knowledge of BP meas-
urement is unlikely to improve during specialised postgraduate
training since the skill is not taught during this period because of
the assumption that the relevant skill should have been acquired
earlier on during undergraduate training.
We did not find any impact of patient-related factors such
as gender, age, weight and BMI on the occurrence of EDP. Our
results differ from earlier reports by Graves
et al
.,
17
who found an
association between increasing age and zero EDP for DBP, and
the findings by Kim
et al
.,
14
who documented greater EDP for
SBP in older patients and women in BP taken by non-physicians,
and greater EDP for DBP in less-obese patients in BP taken by
physicians.
Publications abound in the literature on the debate over
whether mercury sphygmomanometers should be phased out in
clinical practice.
27,28
However, it is likely that mercury manom-
eters will remain in use in clinical settings in Nigeria and many
parts of Africa for a long period of time. This is because of their
low cost of purchase and maintenance (no need for electricity or
battery), their simple design (a simple gravity-based unit with
easy calibration), their arguably infrequent need for repair, their
validation in many clinical circumstances against direct intra-
arterial BP measurement, and the rarity of reported health prob-
lems associated with exposure to elemental mercury enclosed in
sphygmomanometers.
1,28,29
Although the use of automated BP measuring devices may
help in eliminating EDP,
12,29
the recommendation by some of
the manufacturers of these devices to recalibrate them against a
mercury manometer every six months, and the non-elimination
by these devices of other sources of errors in BP measurement,
such as choice of cuff size, placement of cuff, posture of subject,
arm support, etc, argue against the total abandonment of mercury
sphygmomanometers in clinical settings.
28
Studies have also shown that training, retraining and certifi-
cation of healthcare workers in BP measurement with regular
monitoring and feedback on end digit and number preference
help to reduce or eliminate end digit and other observer bias and
errors associated with BP measurement.
12,17,18,28
Our cohort consisted of patients being managed for hyperten-
sion, and good BP control can be defined as SBP
<
140 mmHg
and/or DBP
<
90 mmHg. Only two (3.8%) out of 53 patients
with SBP
<
140 mmHg had SBP of 138 mmHg and two (2.4%)
out of 84 patients with DBP
<
90 mmHg had DBP of 88 mmHg.
Therefore, the occurrence of an 8 as end digit was not related to
treatment thresholds.
2-4
The means of the difference in the nurse–doctor SBP meas-
urements was –4.36 mmHg, indicating that the SBP readings
by the nurses were on the average lower than those by doctors.
However, the nurse–doctor DBP difference of 1.22 indicates that
DBP recorded by the nurses were on the average higher than that
recorded by doctors.
The means and range of the nurse–doctor SBP differences in
our study of –4.36 mmHg and –60 to
+
32 mmHg was compara-
ble to –6.3 mmHg and –67 to +66 mmHg reported by La Batide-
Alanore
et al.
30
from France. Although the mean nurse–doctor
DBP difference in our study was higher than that reported by
La Batide-Alanore
et al.
(1.22 vs –7.9 mmHg), the ranges of
the difference were similar (–44 to
+
40 vs –44 to
+
31 mmHg).
30
This study had a few limitations. The high frequency of zero
EDP in our study is an indication that the various healthcare work-
ers involved in this study were rounding the BP readings to the
nearest 10 mmHg. In view of the retrospective nature of the study,
we could not tell whether the readings were rounded down or up.
Second, we had few missing data on weight (one subject) and
height (nine subjects). Third, in view of its retrospective nature,
we could not assess whether the BP measurements were done
according to the guidelines on BP measurement. Lastly, although
the number of our observations may appear small, most publica-
tions on this subject with larger number of observations involved
multiple centres with electronic storage of BP readings.
12,14-16,18,20,29
Conclusion
We found a high frequency of zero EDP in BP measurements
in our hypertension specialty clinic, particularly from among
the nursing staff and resident doctors. Our findings argue for
the training, retraining and certification of nurses and doctors
in BP measurement and the institution of a regular monitoring
and feedback system on EDP in order to minimise this observer
error.
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