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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 5, September/October 2017
320
AFRICA
(ABX, Montpellier, France). Neutrophil/lymphocyte (N/L) ratio
was calculated by dividing the total neutrophil count by the
lymphocyte count.
High-sensitivity C-reactive protein (hs-CRP) analyses were
done using the immunonephelometry method (Dade Behring,
Inc, BN Prospect, Marburg, Germany). Serum levels of
creatinine, fasting blood glucose, triglycerides, total cholesterol,
and low- and high-density lipoprotein cholesterol were measured
using conventional methods.
A conventional angiography device (Artis zee; Siemens,
Erlangen, Germany) was used for coronary angiography.
Angiograms were evaluated qualitatively by two different experts,
and mean values were used to assess the rate of stenosis. Patients
with atherosclerotic lesions in any of the coronary arteries were
diagnosed as having CAD. Obstructive CAD was defined as
stenosis of
≥
50% of the diameter of a major epicardial or
branch vessel
>
2.0 mm in diameter.
Gensini scores were calculated for each patient as previously
defined.
14
Triple-vessel disease was defined as stenosis of
≥
50%
in each of the major vessels or their major branches. Patients
were evaluated and treated according to the current guidelines.
Statistical analysis
Statistical analysis was performed using commercial software
(IBM SPSS Statistics 22, SPSS Inc, Chicago, IL, USA). After
performing the Kolmogorov–Smirnov normality test, two
independent-sample
t
-tests were used to compare the normally
distributed independent variables, and the Mann–Whitney
U
-test was used to compare the non-normally distributed
independent variables between the two groups. For normally
distributed variables, mean and standard deviation (SD) are
listed, otherwise, median values are given. To analyse the
categorical data, a chi-squared test was used. Categorical data
are expressed as numbers and percentages.
A receiver operating characteristic (ROC) curve was
constructed for RDW to test the effectiveness of various cut-off
points in predicting CAD. The area under the ROC curve was
calculated; the sensitivity and specificity for the RDW of the
most appropriate cut-off point were calculated for predicting
CAD. Correlations were determined using the Spearman test. A
p
-value
<
0.05 was considered statistically significant.
Results
The study group was divided into two, according to angiographic
results (CAD negative and CAD positive). There were no
significant differences between the two groups with regard to age,
gender, hypertension, hyperlipidaemia, smoking, BMI, systolic
and diastolic blood pressure, and medications, including aspirin,
renin–angiotensin system (RAS) blockers and statins (Table 1).
Clopidogrel and calcium channel blocker use was higher in
the CAD-positive group (
p
<
0.001 and
p
=
0.001, respectively)
(Table 1). There were no differences between the two groups
in serum levels of glucose, creatinine, uric acid, hs-CRP, lipid
profile, WBC, haemoglobin, MPV and N/L ratio (Table 1).
RDW was significantly higher in the CAD-positive group (12.5
±
1.5 vs 13.8
±
1.7%,
p
<
0.001) (Table 1).
The most appropriate cut-off point calculated for predicting
CAD was 13.25%. The patients who had a RDW
≤
13.25% were
included in the low RDW group. The rest formed the high RDW
group.
There were no significant differences between the low and
high RDW groups with regard to age, gender, hypertension,
hyperlipidaemia, smoking, BMI, systolic and diastolic blood
pressure andmedications (Table 2). There were also no differences
between the low and high RDW groups with regard to serum
levels of glucose, uric acid, lipid profile, WBC and haemoglobin
(Table 2).
Serum levels of creatinine, hs-CRP, MPV and N/L ratio were
significantly higher in the high RDW group (
p
<
0.005 for all)
(Table 2). RDW was positively correlated with hs-CRP, MPV
and N/L ratio (
r
=
0.248,
r
=
0.240 and
r
=
0.281, respectively and
p
=
0.033 for hs-CRP,
p
<
0.001 for MPV and N/L ratio).
Patients with CAD who had a RDW value above the cut-off
point also had higher Gensini scores, higher percentages of
obstructive CAD and triple-vessel disease (
p
≤
0.001 for all)
(Table 3). According to the cut-off values calculated using ROC
curve analysis, RDW
>
13.25% had a high diagnostic accuracy
for predicting CAD (area under the ROC curve
=
0.742,
p
<
Table 1. Baseline characteristics and laboratory
findings of the study groups
Variables
CAD
–
(
n
=
109)
CAD+
(
n
=
124)
p-
value
Age (years)
58.6
±
8.0
57.7
±
9.0
0.387
Gender (male)
61 (56)
68 (55)
0.895
Hypertension
93 (85)
104 (84)
0.856
Dyslipidaemia
61 (56)
77 (62)
0.353
Smoking
14 (13)
24 (20)
0.215
Aspirin
72 (66)
93 (75)
0.150
Clopidogrel
0 (0)
23 (19)
<
0.001
RAS blockers
70 (64)
93 (75)
0.086
β
-blockers
34 (31)
66 (53)
0.001
Calcium channel blockers
20 (18)
23 (19)
1.000
Statins
30 (28)
43 (38)
0.260
Body mass index (kg/m
2
)
28.7
±
5.0
28.3
±
4.5
0.536
Systolic blood pressure (mmHg)
130
±
13
132
±
14
0.144
Diastolic blood pressure (mmHg)
78
±
9
79
±
8
0.627
Glucose (mg/dl)
166
±
75
174
±
78
0.416
[mmol/l]
[9.21
±
4.16]
[9.66
±
4.33]
Creatinine (mg/dl)
0.73
±
0.18
0.71
±
0.28
0.630
[μmol/l]
[64.53
±
15.91]
[62.76
±
24.75]
Uric acid (mg/dl)
4.5
±
1.4
4.9
±
1.7
0.081
hs-CRP (mg/l)
5.12
±
2.93
6.07
±
4.83
0.348
Total cholesterol (mg/dl)
197
±
40
199
±
49
0.726
[mmol/l]
[5.10
±
1.04]
[5.15
±
1.27]
Triglycerides (mg/dl)
187
±
86
191
±
138
0.786
[mmol/l]
[2.11
±
0.97]
[2.16
±
1.56]
LDL cholesterol (mg/dl)
120
±
36
122
±
44
0.688
[mmol/l]
[3.11
±
0.93]
[3.16
±
1.14]
HDL cholesterol (mg/dl)
46
±
11
45
±
13
0.283
[mmol/l]
[1.19
±
0.28]
[1.17
±
0.34]
WBC (10
3
cells/µl)
7.0
±
1.9
7.2
±
2.0
0.407
Haemoglobin (g/dl)
13.1
±
1.1
13.1
±
1.6
0.757
RDW (%)
12.5
±
1.5
13.8
±
1.7
<
0.001
MPV (fl)
8.43
±
1.10
8.59
±
1.02
0.265
Neutrophil/lymphocyte ratio (%)
2.26
±
1.37
2.52
±
1.94
0.457
CAD: coronary artery disease, CAD–: patients with normal coronary arteries,
CAD+: patients with coronary artery disease, RAS: renin–angiotensin system,
hs-CRP: high-sensitivity C-reactive protein, LDL: low-density lipoprotein,
HDL: high-density lipoprotein, WBC: white blood cells, RDW: red cell distribu-
tion width, MPV: mean platelet volume. Data are shown as
n
(%) or mean
±
SD