Evaluation of Reliability of Pre- and Post-
Dialytic Measurements through Home Blood
Faye Moustapha*, Faye Maria, Lemrabott Ahmed Tall, Cisse Mouhamadou Moustapha, Daher
Abdoul Karim Omar, Fall Khodia, Sakho Binta, Keita Rick Alex Ismael, Mbengue Mansour,
Niang Abdou, Diouf Boucar and Ka Elhadji Fary
Nephrology Department, Aristide Le Dantec University Hospital, Cheikh Anta Diop University, Dakar, Senegal.
Faye Moustapha, Aristide Le Dantec University Hospital, Cheikh Anta Diop University, Dakar, Senegal, BP 3001Pasteur,
Tel: +221 77 665 65 68; E-mail:
Received: June 13, 2018; Accepted: June 15, 2018; Published: June 20, 2018
Moustapha F, Maria F, Ahmed Tall L, et al. (2018) Evaluation of Reliability of Pre- and Post-Dialytic Measurements through Home Blood Pressure Monitoring. J UrolNephrol Open Access 4(1): 1-5. DOI: 10.15226/2473-6430/4/1/00139
There is a significant dispute about the ideal moment for the taking
the blood pressure and the target values. The aim of our study was to
assess the sensitivity, specificity, positive predictive value and negative
predictive value of the blood pressure measurement before and after
hemodialysis, at a hemodialysis center in sub-Saharan Africa. It was
a multicenter, cross-sectional study, conducted from 25 April 2016 to
18 June 2016. All chronic hemodialysis patients who take home blood
pressure, pre- and post-dialytic session for one week were included.
We calculated sensivity, specificity, positive predictive value and
negative predictive value. The mean age of patients was 45.57 years
± 14.11 with a sex ratio of 1.42. The mean duration of hemodialysis
was 57.96 months ± 34.86. Predialytic measures: sensivity was 72.7
% and specificity 53.8%; positive predictive value 80% and negative
predictive value 43.8 %. Post-dialytic measures: sensitivity was 90.9 %
and specificity of 38.5%; positive predictive value 78.9% and negative
predictive value 62.5%. Pre- and post-dialytic measures are not
reliable in the diagnosis of hypertension in hemodialysis.
Keywords: reliability - HBPM – hemodialysis – Dakar;
Hypertension (HTN) is defined as blood pressure (BP) greater
than 140 mmHg for systolic and / or greater than 90 mmHg for
diastolic . Pre-dialysis HTN is defined by BP values greater than
or equal to 140 mmHg for systolic and / or 90 mmHg for diastolic
 and post-dialysis HTN with BP values greater than or equal
to 130 mmHg for systolic and / or 80 mmHg for diastolic . BP
control is important for reducing cardiovascular morbidity and
mortality in chronic hemodialysis (CHD) patients . However,
there is strong difference of opinion among this population
regarding the ideal timing for BP measurement. The accurate
diagnosis of hypertension in hemodialysis patients is difficult
because of the large fluctuations in BP during the hemodialysis
session . Thus, there is uncertainty about the development of
an accurate diagnosis of HTN in CHD patients by conventional
measurement at the center . Now, home blood pressure
monitoring (HBPM) and ambulatory blood pressure monitoring
(ABPM) remain essential in the diagnosis of hypertension. No
work has been done on this subject in Senegal, due to which we
undertook this study with the aim of assessing sensitivity (Sen),
specificity (Spe), positive predictive value (PPV) and negative
predictive value (NPV) of BP measurement before and after
hemodialysis sessions in sub-Saharan African hemodialysis
Patients and method
Design of study
This was a cross-sectional and multicenter observational
study that took place over a month and 23 days (25 April 2016 to
18 June 2016) in the hemodialysis units of the Aristide Le Dantec
Hospital and the Grand Yoff General Hospital. All patients who
could take BP at home using an electronic BP machine and put
it on a self-measurement form, and who signed written consent
after receiving an explanation, were included in the study.
Patients with chronic hypotension were not included and those
with less than 50% of records were excluded.
Patients would independently take home BP twice a day,
per the usual criteria for validity of the measure and write it
on a pre-established statement form . They performed three
consecutive measurements at one minute intervals, at least five
minutes rest, morning before breakfast, and before bedtime and
taking medication. Compared to the traditional 3 day HBPM, we
asked patients to perform 6 days of HBPM to analyze the different
interdialytic periods . The measurements of the first day were
excluded from the interpretation. The average of the other values
was calculated and represents the average BP obtained by HBPM.
Usual measurements made by early-stage dialysis nurses
taken after five minutes of rest just before the session is
connected; the end of session BP after restitution were collected
on a pre-established survey sheet during the same 6 days. The
same electronics BP machine (OMRON or SPENGLER) was
used by the patient in HBPM and by the nurse in conventional
The definitions used for the diagnosis of pre- and post-dialytic
HTN are those of KDOQI 2005 , viz., in HBPM, an average
weekly BP greater than or equal to 135 mmHg for systolic and /
or 85 mmHg for diastolic . Based on these definitions, patients
were classified into four groups: permanent hypertensive (PH),
permanent normo-tensive (PN), hypertensive white coat (WC)
and masked hypertensive (MH). MH was defined by normal BP in
CM and high BP in HBPM, WC with high BP in CM and normal BP
in HBPM. PH was defined by high BP in HBPM and in CM and PN
by normal BP in HBPM and in CM.
Data was captured and analyzed utilizing the Sphinx
software, version 126.96.36.199. A descriptive study was performed with
the calculation of frequencies and proportions for qualitative
variables and calculation of the means and standard deviation for
Sensitivity (Sen), specificity (Spe), positive predictive value
(PPV) and negative predictive value (NPV) were calculated as per
the following formulas :
sen=TP/(TP+FN); Spe=TN/(TN+FP); PPV=TP/(TP+FP);
TP (true positive) = PH; TN (true negative) = PN; FP (false
positive) = WC; FN (false negative) = MH
The number of patients included in the study was 49 which
is 33.8% of the total of 136 patients. Of these patients, 3 were
excluded: 2 with less than 4 measures and 1 having lost their
HBPM record. A total of 46 patients were retained [Graphic 1].
The main characteristics of these patients are shown in [Table
1]. The mean-age was 45.57 years ± 14.11 with a sex ratio of
1.42. The mean duration of dialysis was 57.96 months ± 34.86.
Hypertensive nephropathy was more common, noted in 20
patients or 43.5%, while nephropathy was indeterminate in 7
patients, accounting for 15.2%. Residual diuresis was present
in 14 patients (30.4%). Of the 46 patients, 17 (37%) were on
erythropoietin, 4 patients (8.7%) on iron and 31 patients (67.4%)
on anti-hypertensive drugs [Graphic 2], with an average of 2
molecules ± 1.06. The mean hemoglobin level was 9.65 g / dl ±
2.20. Left ventricular hypertrophy (LVH) was noted in 15 patients
(36.6%). HBPM compliance was 100% in 71.7%.
The mean pre-dialysis BP was 145.98 / 86.03 mmHg and
post-dialysis BP was 140.79 / 85.6 mmHg. The mean BP in HBPM
was 137.61/ 87.37 mmHg [Table 2]. BP was elevated in 38
patients (82.6%) in pre- and post-dialysis. It was systolo-diastolic
in 68.4% in predialysis and 63.2% in post-dialysis.
For pre-dialysis measurements, Sen was 72.7%, Spe 53.8%,
PPV 80% and NPV 43.8%.
For post-dialysis measurements: Sen was 90.9%, Spe 38.5%,
PPV78.9% and NPV 62.5% [Table 3].
Graphic 1: Study design
Table 1: Clinical, biological and therapeutic characteristics of 46
patients in the hemodialysis units of the Aristide Le Dantec Hospital
and the Grand Yoff General Hospital.
All patients, n=46
45.57 ± 14.11
Duration in dialysis (months)
57.96 ± 34.86
Gender, n (%)
Interdialytic weight gain, n (%)
3,52 ± 1.72
MBI, mean (Kg/m2)
Overweight, n (%)
Obesity, n (%)
Thinness, n (%)
21.88 ± 4.06
Intradialytic Hypotension, n (%)
Hemoglobin, mean (g/dl)
9.65 ± 2.20
Serum calcium, mean (mg/l)
88.79 ± 6.75
LVH, n (%)
Erythropoietin, n (%)
Antihypertensive drugs, n (%)
Number of antihypertensive drugs, mean
Monotherapy, n (%)
Bitherapy, n (%)
Tritherapy, n (%)
Pentatherapy, n (%)
2 ± 1.06
Graphic 2: Main drugs used in the treatment of hypertension
in 46 chronic hemodialysis patients in 2 hemodialysis centers in
Table 2: Mean blood pressure in home blood pressure measurement,
predialysis and postdialysis measurement of 46 patients in the
hemodialysis units of the Aristide Le Dantec Hospital and the Grand
Yoff General Hospital.
HBPM (mm Hg)
137.61 ± 21.45
87.37 ± 13.93
CM (mm Hg)
145.98 ± 18.78
86.03 ± 13.22
140.79 ± 24.20
85.60 ± 14.52
Table 3: Sensitivity, specificity and predictive value of the measures of
46 patients in the hemodialysis units of the Aristide Le Dantec Hospital
and the Grand Yoff General Hospital.
Definition of HTN (mm Hg)
In our study, the predialysis measurement was less sensitive,
but more specific than the post-dialysis measurement. Thus, the
post-dialysis measurement had less false-negative, while the predialytic
measurement had fewer false positives. The same result
is reported by Kaze Folefack F et al. in Lomé and Doukkali et al.
in Morocco [9, 10]. The ideal threshold of blood pressure for the
diagnosis should have a Sen and Spe of 100% . These measures
should ideally give an unequivocal answer to the diagnostic
question relating to the presence of HTN if the measurement is
positive, and its absence, if negative. Our study shows that BP
measurements at the center have limited performance in the
diagnosis of HTN in hemodialysis patients.
If BP is elevated pre- or post-dialysis, what is the probabilitythat the patient is truly hypertensive; and if BP is normal preor
post-dialysis, what is the probability that the patient is not
hypertensive? We calculated the PPV and the NPV. Our study
revealed that a patient with pre- or post-dialysis HTN was
respectively 80% and 78.9% likely to have HTN. In addition, a
patient with pre- or post-dialysis normal BP had respectively
43.8% and 62.5% probability of not being hypertensive.
The results of CM should be confirmed by HBPM or at best
by ABPM. These results also show that all hemodialysis patients
should benefit from HBPM or ABPM, even if their BP is normal
at the center. Moreover, it would be better for them to evaluate
inter-dialytic BP, adopt the dry weight and the anti-hypertensive
drugs, and estimate the level of overall cardiovascular risk of the
patient . However some authors like zoccali, feel that it is of
little use considering ABPM as the gold standard for definition
of hypertension in the dialysis population, because there is no
solid evidence that ABPM is superior to repeated pre-dialysis
measurements (the average monthly value) .
In our study, pre-dialysis measurement was less sensitive,
but more specific than post-dialysis measurement. Both
measurements have low specificity. This result confirms the
difficulties in the diagnosis of hypertension in hemodialysis
by pre- and post-dialysis measures. However, these measures
do have their place in the supervision of the tolerance of the
hemodialysis sessions. Thus, the HBPM makes it possible to better
estimate the inter-dialytic BP, is extremely useful for adapting the
dry weight and anti-hypertensive drugs, and for estimating the
level of overall cardiovascular risk of the patient. Policies must be
put in place to make electronic devices accessible.
Limitation of the Study
All the same, our study has limitations of cohort size and
selection bias, as only educated patients were included.
Conflicts of interest
The authors declare not to have any conflict of interest in
relation to this article.
Contributions of the authors
All authors have read and approved this version of the
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