CARDIOVASCULAR JOURNAL OF AFRICA • Vol 24, No 7, August 2013
AFRICA
275
Statistical analysis
Analysis was performed with software review manager 5.1
(Cochrane collaboration,
) and
comprehensive meta-analysis (Englewood, NJ);
p
<
0.05 was
regarded as statistically significant. Meta-analysis was performed
in fixed- or random-effect models.
Odds ratios (OR) and 95% confidence intervals (CI) were
estimated in each study. Pooled ORs were obtained using the
Mantel-Haenszel method in a fixed-effect model, and the
DerSimonian-Laid method in a random-effects model.
24
The
significance of pooled ORs was determined by the
Z
-test.
Cochrane’s
Q
-statistic was used to assess within- and between-
studies variations. A
p
<
0.10 on the
Q
-statistic was regarded
as heterogeneity across the studies.
I
2
was also used to test
heterogeneity with the formula:
I
2
=
(
Q
− df)
_______
Q
×
100%
where
I
2
<
25% means no heterogeneity;
I
2
=
25–50% means
moderate heterogeneity;
I
2
>
50% means large or extreme
heterogeneity.
27
The random-effects model was also used for evaluating the
possibility of heterogeneity of studies. Publication bias was
evaluated with Egger’s test and funnel plots,
28
which compensate
for each other’s drawbacks. If there is evidence of publication
bias, the funnel plot is noticeably asymmetric. For the Egger’s
test the significance level was set at 0.05. Sensitivity analysis
was also performed to test reliability of the results, by removing
one study at a time and repeating the meta-analysis.
Results
As shown in Fig. 1, among 3 658 articles potentially relevant to
the search terms (PubMed: 1 103; MEDLINE: 765; Springer:
650; Elsevier Science Direct: 880; Cochrane Library: 50; Google
Scholar: 210), 323 potentially relevant studies were selected after
the duplicates were removed. When the abstracts were screened,
276 were excluded (65 were review articles, 156 were not diabetic
patients, 55 did not report on BMS data). Among the remaining
47, another 41 were excluded (25 only reported on BMS data
without comparisons, 16 were excluded due to unavailable data).
Finally, six studies were included in this meta-analysis.
The characteristics of the included studies are presented in
Table 1. These six studies were conducted from 2002 to 2006
and published between 2005 and 2008, three in Europeans,
two in Americans, and one in Asians and Americans. A total
of 1 259 CAD subjects with diabetes (SES 614 and BMS 645)
were included, with an average age of 65 years. The sample
sizes ranged from 83 to 458, and the studies were RCTs and
non-RCTs.
3 658 potentially relevant reports identified and screened
(Pubmed, 1103; MEDLINE, 765; Springer, 650; Elsevier Science
Direct, 880 Cochrance Library, 50; Google Scholar 210)
323 excluded by review of abstract
(65 reviews; 156 not diabetic
patients; 55 not reported BMS data)
41 excluded by review of full text
(25 for only reported EMS data but
not for comparison; 16 due to not
available data)
323 potentially relevant reports after duplicates removed
47 retrieved for detailed assessment
6 separate studies included in meta-analysis
Fig. 1. Flow chart of selection of the studies.
TABLE 1. CHARACTERISTICS OF STUDIES INCLUDED IN THE META-ANALYSIS
Study
Study year
Country
Ethnicity
Study
method
Follow
up
(years)
SES group
BMS group
Sample
size Age (years)
Sample
size Age (years)
Aoki J,
et al
.
2002–2003
Netherlands
European
Non-RCT 1
112
63
±
10 118 64
±
11
Jimenez-Quevedo P,
et al
.
2003
United States
America
RCT
1
80 65.4
±
8
80 67.9
±
9
Baumgart D,
et al
.
2002–2004
Germany
European
RCT
1
94
66
±
9
96 66
±
10
Daemen J,
et al
.
2002–2003
United States
America
Non-RCT 1
206 62.0
±
10 252 62.7
±
10
Chan C,
et al
.
2002–2004 United States and Asia America and Asian RCT
1
54 58.7
±
9.7 29 62.5
±
10.3
Maresta A,
et al
.
2004–2006
Italy
European
RCT
1
68
71
±
9
70 69
±
9
TABLE 2. POOLED ODDS RATIO FOR THE SES VERSUS THE BMS GROUP
Subgroups
No. of
studies
Random model
Test of heterogeneity
Egger’s test for publication bias
OR (95% CI)
Z
p value
Q p-value
I2 (%)
t
p-value
Overall effects
6
0.42 (0.24–0.74)
3.00
<
0.01
20.14
<
0.01
75.2
–4.19
0.014
Sample size
≤
90
3
0.28 (0.16–0.48)
4.60
<
0.01
2.39
0.303
16.3
–3.66
0.62
Sample size
>
90
3
0.61 (0.31–1.21)
1.42
0.15
8.70
0.013
77.0
–9.26
0.20
RCT
4
0.28 (0.19–0.42)
6.14
<
0.01
2.40
0.495
0.0
–2.36
0.531
Non-RCT
2
0.87 (0.61–1.24)
0.76
0.446
0.92
0.338
0.0
–5.29
–
European
3
0.45 (0.27–0.77)
2.95
<
0.01
3.71
0.156
46.1
–7.98
0.46
American and Asian
3
0.37 (0.11–1.27)
1.58
0.115 15.55
<
0.01
87.1
–5.92
0.23
