The relationship between red blood cell distribution width and blood pressure in patients with type 2 diabetes mellitus in Lagos, Nigeria
Journal of Blood Medicine
The relationship between red blood cell distribution width and blood pressure in patients with type 2 diabetes mellitus in Lagos, Nigeria
Olusola Akinola Dada 2
Ebele Uche 1
Akinsegun Akinbami 1
Majeed Odesanya 0
Sarah John-Olabode 6
Adewumi Adediran 5
Olajumoke Oshinaike 2
Olaitan Okunoye 4
Olanrewaju Arogundade 1
Kingsley Aile 3
Timothy Ekwere 7
0 Oak Hospitals , Ikorodu, Lagos , Nigeria
1 Department of Haematology and Blood Transfusion, Lagos State University, College of Medicine , Ikeja , Nigeria
2 Department of Medicine, Lagos State University
3 Department of Haematology and Blood Transfusion, Lagos State University Teaching Hospital , Ikeja , Nigeria
4 Department of Medicine, University of Port Harcourt , River State
5 Department of Haematology, Faculty of Clinical Sciences, College of Medicine, University of Lagos , Idiaraba
6 Department of Haematology, Ben Carson School of Medicine, Babcock University , Ilisan-Remo , Ogun State
7 Department of Haematology and Blood Transfusion, University of Uyo , Akwa Ibom , Nigeria
PowerdbyTCPDF(ww.tcpdf.org) O R I G I N A L R E S E A R C H Background: High red blood cell distribution width (RDW) is related to impairment of erythropoiesis, reflecting chronic inflammation and increased levels of oxidative stress, both of which are telltale signs of type 2 diabetics. The aim of this study was to evaluate the relationship between the RDW and fasting blood sugar/blood pressure, and compare the results from diabetics with nondiabetic controls. Methods: This was an unmatched case-control study involving 200 participants consisting of 100 diabetics and 100 nondiabetic controls. Blood (4.5 mL) was collected from all of the diabetics and nondiabetic controls, and placed into EDTA anticoagulant tubes. A full blood count was performed using the Sysmex KX-21N, a three-part auto analyzer able to run 19 parameters per sample, including RDW. Blood pressure was measured during sample collection and in a sitting position. Results: The mean fasting blood sugar level was 95.20±30.10 mg/dL in the controls, and 147.85±72.54 mg/dL in the diabetics. The mean blood pressures for diabetics was 138/90 mmHg and for non-diabetics 120/80 mmHg. The mean RDW-SD (RDW standard deviation) was 46.44±4.64 fl in the controls, and 46.84±3.18 in the diabetics. The mean RDW-CV (RDW coefficient of variation) was 14.74%±1.94% in controls, and 14.80±0.71 for diabetics. No statistically significant correlation was found between the RDW-SD and fasting blood sugar/blood pressure in the diabetics. A statistically significant positive correlation was found between the
RDW; fasting blood sugar; type 2 DM
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RDW-CV and blood pressure in the diabetics.
Conclusion: A positive correlation between the RDW-CV and blood pressure was established
in the diabetics in this study.
Diabetes mellitus (DM) is a chronic metabolic disorder characterized by hyperglycemia,
and resulting from defects in insulin secretion, insulin action, or both.1 The chronic
hyperglycemia occurring in DM is associated with long-term damage, as well as
dysfunction and failure of different organs, especially in the eyes, kidneys, nerves, heart
and blood vessels.1 The World Health Organization (WHO) estimates that about 347
million people worldwide are presently living with DM.2 Of this figure, approximately
80% are from low and medium income countries.
3 WHO also projects that by 2030
DM will be the seventh leading cause of death worldwide.4 There are two main types
of DM: type 1 which usually develops in childhood and adolescence, and is insulin
dependent; and type 2 which develops in adulthood and represents more than 90%
of cases worldwide. Risk factors for type 2 DM include
sedentary lifestyle, obesity, and old age.
Diagnosis of DM can be made with a simple fasting
plasma glucose test with values $126 mg/dL (7.0 mmol/L)
being diagnostic of DM (fasting is defined as no caloric
intake for at least 8 hours).5 In the presence of
symptoms of hyperglycemia (polyuria, polydipsia, polyphagia,
weight loss), a casual plasma glucose level of .200 mg/dL
(11.1 mmol/L) is diagnostic.5
Recently, various researchers have proposed that type 2 DM
is connected to a state of subclinical chronic inflammation.6,7
It may be that abnormal levels of chemokines released by the
expanded adipose tissue in obesity activates monocytes, and
increases the secretion of proinflammatory adipokines. Such
cytokines in turn enhance insulin resistance in adipose and
other tissues, thereby increasing the risk of type 2 DM.8,9
The red blood cell distribution width (RDW) is a
measure of variation in size of the circulating erythrocytes
.rvepedo l.ysneo (aauntoismocaytetodsciso)m10pwlehtiechbliosordouctoinuenlty. HobigtahinRedDWfromindaicsatatensdathrde
/www laun presence of anisocytosis which is related to impairment of
tsp rse erythropoiesis and degradation of erythrocytes,10 reflecting
rom oF chronic inflammation and increased levels of oxidative stress,
fd both of which are telltale signs in type 2 diabetics, and this
ade may significantly contribute to development of
atherosclelonw rotic diseases.11,12
edo Many recent studies have investigated changes in RDW
iicn in association with cardiac and noncardiac related deaths.13–19
deM Most of these studies report a positive correlation of RDW
lood with the erythrocyte sedimentation rate (ESR) and C-reactive
foB protein (CRP) levels – an increase in the RDW during
lran inflammation, similar to that seen in other inflammatory
Jou parameters. Malandrino et al20 recently reported a positive
correlation between a high RDW and increased incidence of
both macro- and microvascular complications in DM patients
without marked vascular complications.
The aim of this study was to evaluate the relationship
between the RDW and fasting blood sugar/blood pressure,
and compare with nondiabetic controls.
The research was approved by the Ethics Review Committee
of Lagos State University Teaching Hospital (LASUTH).
This was a case-control study consisting of 100 type 2 DM
patients receiving treatment, attending the diabetic clinic of the
LASUTH, and 100 nondiabetic controls consisting of medical
students, nurses and doctors in the same institution. During
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the study period between June to September 2013, all patients
who gave informed consent and satisfied the study inclusion
criteria were recruited into the study. They were asked to fill
structured questionnaires including demographic information,
height, weight, last fasting blood sugar, blood pressure, drug
history, and family history of diabetes. All the diabetics were
on oral hypoglycemic and antiplatelet drugs, like clopidogrel
and vasoprin tablets, and some were on antihypertensive and
lipid lowering drugs. Information on family history of diabetes
was also obtained from the controls and they were subjected
to fasting blood sugar testing before enlistment.
Blood was withdrawn with minimal stasis from the
antecubital vein using a dry sterile disposable syringe and needle.
Blood (4.5 mL) was dispensed into EDTA anticoagulant
tubes. The specimens were labeled with subject’s age, sex, and
identification number. The EDTA samples were kept at room
temperature until processed within 4 hours of collection.
A full blood count was performed using the SysmexKX-21N
(Sysmex Corporation, Kobe, Japan), a three-part auto
analyzer able to run 19 parameters per sample, including
hemoglobin concentration, packed cell volume, red blood
cell concentration, mean corpuscular hemoglobin, mean
cell volume, mean corpuscular hemoglobin
concentration, white blood cell and platelet count, and mean platelet
volume. Standardization, calibration of the instrument, and
processing of the samples were carried out according to the
Well-mixed blood samples were aspirated, by leaving
the equipment sampling probe in the blood sample and then
pressing the start button. Approximately 20 µL of blood was
aspirated by the auto analyzer. The results of the analysis
were displayed after about 30 seconds.
Data were analyzed using SPSS version 16.0 (SPSS Inc.,
Chicago, IL, USA). The continuous variables were given as
means ± standard deviation (SD). The Pearson chi- squared
test was used to test for association between discrete
variables. The P-value was considered to be statistically
significant when less than 0.05.
A total of 200 participants were enrolled into the study –
consisting of 100 diabetics and 100 nondiabetic controls.
The mean age of the control group was 32.38±6.44 years,
with a minimum age of 17 years, and a maximum age
of 70 years. The mean age of the type 2 DM group was
62.35±9.84 years, the minimum was 34 years old, and the
maximum 90 years old. The overall female:male ratio was
68% to 32%. In the type 2 DM participants, 73% were
female, and 27% were male. In the nondiabetic participants,
63% were female, and 37% were male (Table 1).
In the diabetic group, the mean body mass index was
32.10±4.85 kg/m2, and the mean fasting blood sugar level
was 147.85±72.54 mg/dL. In the nondiabetic group, the
mean body mass index was 25±5.23 kg/m2, and the mean
fasting blood sugar was 95.20±30.10 mg/dL. The minimum
blood pressure of the diabetics was 100/90 mmHg,
maximum was 200/90 mmHg, and the mean was 138/90 mmHg.
Amongst the diabetics, a total of 45 out of 100 (45%) gave
a positive family history of type 2 diabetes, while 55% had
no family history of diabetes. Only 5% of the controls gave
a positive family history of diabetes. The mean duration of
diabetes in the type 2 DM group was 8.81±7.06 years. The
RDW-CV (RDW coefficient of variation) in the control group
was 14.74±1.94, and 14.80±0.71 in the type 2 DM group.
The RDW-SD (RDW standard deviation) was 46.44±4.64 in
the control group, and 46.84±3.18 in the type 2 DM group
Both the RDW-SD and the RDW-CV were not
statistically significantly correlated with the fasting blood sugar
level in the type 2 DM group; P-values were 0.10 and 0.55
respectively; Spearman’s rho values were -0.61 and -0.12
respectively. The RDW-SD was not statistically significantly
correlated with blood pressure; P=0.99; Spearman’s rho of
0.11. A statistically significant correlation was achieved
between the RDW-CV and the blood pressure of type 2 DM
patients; P=0.02, Spearman’s rho of 0.02. RDW-SD and the
RDW-CV values were not statistically significantly correlated
with the duration of diagnosis of diabetes in the patients;
P-values were 0.8 and 0.38 respectively; and Spearman’s rho
of 0.096 and -0.035 respectively.
Tukey’s post hoc analysis could not be performed between
the RDW-CV and blood pressure because at least one group
had fewer than two cases, the significant level of 0.29 was
obtained with test of homogeneity of variance.
DM affects a sizeable proportion of the working population,
and has economic consequences for both the individual and
the society as a whole. Thus, the monitoring of DM in order
to prevent complications is urgently needed. The RDW,
a widely available and inexpensive test conducted as part
of the complete blood cell count, measures the degree of
anisocytosis. It is calculated as follows:
RDW-CV = (Standard deviation of red blood cell
volume ÷ mean cell volume) ×100
The normal range for the RDW-CV is 11.5%–14.5%, and
higher values indicate greater variations in cell sizes.21 High
RDW indicates a high degree of anisocytosis which is
associated with distortion and degradation of erythropoiesis,21
reflecting chronic inflammation and an increased level of
DM increases vascular inflammation and oxidative stress
while vascular inflammation affects erythropoiesis and
deformability of red blood cells thus elevating RDW levels.23
RDW is strongly associated with chronic inflammation and
is a strong indicator of risk of cardiovascular mortality in
people with cardiovascular diseases, DM, as well as in the
Increased RDW may also arise as a result of anemia. Thus,
causes like iron deficiency, and megaloblastic anemia with
associated micro- or macrocytosis are potential confounders
because our participants were not screened for iron, vitamin
12, nor folic acid. However, the effect of such confounders is
negligible as all the participants selected for the study were
healthy individuals (control group) and diabetics without
complications or obvious comorbidities as at the time of the
study. The effect of other causes of chronic inflammation such
as tuberculosis, cancers, and connective tissue disorders as
confounders is similarly negligible.
The mean age of diagnosis of type 2 DM among adults
aged 18–79 years in the US between 1997 and 2011 was
54 years,25 and is similar to the 62.35±9.84 years obtained
in our study; however this value doubles the mean age of
our controls of 32.38±6.44 years. All controls used for this
study were relatively young men and women working in our
institution including nurses, doctors, and medical students,
which are not representative of the general population; this
could impact on results obtained and is a possible limitation
of the study. However, the sex distribution in the type 2 DM
group and the control group was similar, with approximately
2:1 female:male in both cases.
Our type 2 DM study population had relatively well
.rvepedo l.ysneo type 2 DM group (14.80±0.71 and 46.84±3.18) was almost
controlled diabetes, hence RDW-CV and RDW-SD of the
/www laun the same with control values (14.74±1.94 and 46.44±4.64).
tsp rse Also, the mean fasting blood sugar of 147.85±72.54 mg/dL
rom oF in diabetics compared well with the nondiabetic controls
of 95.20±30.10 mg/dL. These closely related results in our
study may be accounted for by the fact that the majority of
diabetics enrolled had long been on treatment before this
study, and their medications performed well.
We found no significant association between the RDW
and the duration of diabetes. This finding is in contrast with
the findings of studies by Lee and Partley,26 Malandrino et al20
and Heba et al27 who found significant associations between
the RDW and macrovascular complications of DM,
suggesting that RDW may be a predictor of the onset of diabetic
Also in contrast to the studies of Malandrino et al20 and
Sherif et al,27 our results showed a statistically insignificant
negative correlation between RDW and fasting blood sugar
levels in diabetics. While in keeping with many other studies,28–31
a statistically significant positive correlation was achieved
between RDW and blood pressure in our patients.
Elevated RDW had been reported as a prognostic marker
reflecting an underlying inflammatory state.28 High RDW was
strongly associated with poor clinical outcomes in patients
with heart failure,28 coronary artery disease,29,30 pulmonary
hypertension31 and peripheral arterial disease.32 Increased
RDW was also associated with increased mortality in diabetic
patients with coronary artery disease treated with
percutaneous coronary intervention.33
We could only establish a statistically significant correlation
between RDW and blood pressure, not between RDW and
fasting blood sugar. Some of the limitations of this study
could have impacted our results.
We appreciate the efforts of Mr Isa Usman who assisted
in blood collection from the participants, and Mr Phillip O
Oluwamuhuru who carried out the full blood count on the
The authors have no conflicts of interest in this work.
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