CARDIOVASCULAR JOURNAL OF AFRICA • Volume 25, No 1, January/February 2014
30
AFRICA
In individuals diagnosed with the metabolic syndrome from
the JIS definition (
n
=
171), the most frequent components were
elevated blood pressure: 52.5% (men 55.4% vs women 49.82%,
p
=
0.165), reduced HDL-C levels: 50.1% (men 36.7% vs
women 62.3%,
p
<
0.001) and high WC: 39.8% (men 15.3% vs
women 62.3%,
p
<
0.001). The less frequent components were
elevated glucose levels: 23.4% (men 25.9% vs women 21.2%,
p
=
0.172) and raised triglyceride levels: 10.7% (men 12.6% vs
women 9.0%,
p
=
0.155).
Although the prevalence of the metabolic syndrome diagnosed
from the JIS criteria was higher than with the ATP III criteria,
there was good agreement between the two classifications in
the overall sample [kappa
=
0.712, (
p
<
0.001; 95% CI: 0.648–
0.777)], as well as in men [kappa
=
0.624 (
p
<
0.001; 95% CI:
0.493–0.755)] and in women [kappa
=
0.731 (
p
<
0.001; 95%
CI: 0.654–0.809)].
Fig. 1 shows results from the ROC curve analysis to
identify subjects with two or more components of the metabolic
syndrome using the JIS criteria. In men, the optimal cut-off
value of WC to detect the metabolic syndrome with maximum
sensitivity and specificity (Youden index
=
0.563) was 87.5 cm
(sensitivity 75.9%, 95% CI: 62.4–86.5; specificity 81.2%, 95%
CI: 75.7–86; positive predictive value (PPV) 44.2%, 95% CI:
38.5–49.9 and negative predictive value (NPV) 94.2%, 95% CI:
91.5–96.9); whereas in women, the optimal cut-off value of WC
(Youden index
=
0.489) was 80.5 cm (sensitivity 88.4%, 95% CI:
81.3–93.5; specificity 60.5%, 95% CI: 53.4–67.3; PPV 57.5%,
95% CI: 52.1–62.9 and NPV 89.6%, 95% CI: 87.9–91.3).
There was good accuracy (
p
<
0.001) of the cut-off values of
the WC to predict other components of the metabolic syndrome,
as suggested by values of the area under the ROC curve [men:
0.85 (95%CI: 0.80–0.89) and women: 0.79 (95%CI: 0.74–0.84)].
Discussion
The main findings of this study were a high prevalence of the
metabolic syndrome among our subjects and a different cut-off
value for WC for the diagnosis of the metabolic syndrome from
those recommended for Africans by other studies.
5,7
To our
knowledge, this is the first study reporting the prevalence of the
metabolic syndrome in Angolans.
Table 4. Prevalence of the metabolic syndrome from
jis criteria in men and women according to
socio-economic class and educational level
Number (%)
p
-value
Men
Socio-economic class
0.083
Low
8 (9.9)
Middle
13 (16.9)
Upper middle
11 (16.7)
Upper
18 (25.7)
Education level
0.444
Low
15 (13.6)
Medium
12 (17.4)
High
23 (20.0)
Women
Socio-economic class
0.199
Low
29 (39.7)
Middle
28 (35.4)
Upper middle
26 (30.2)
Upper
38 (45.8)
Education level
0.294
Low
45 (43.7)
Medium
27 (33.3)
High
49 (35.8)
Values are number of subjects (
n
) and percentages (%).
1.0
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
Specificity
Sensitivity
Men
Diagonal segments are produced by ties.
1.0
0.8
0.6
0.4
0.2
0.0
0.0
0.2
0.4
0.6
0.8
1.0
Specificity
Sensitivity
Women
Diagonal segments are produced by ties.
Fig. 1.
Receiver operating characteristic (ROC) curves of waist circumference (WC) to detect the metabolic syndrome in men and
women, according to the Joint Interim Statement definition. Area under the ROC curve: 0.85 in men and 0.79 in women.
WC cut-off values in men: 87.5 cm (sensitivity 75.9%, specificity 81.2%) and 80.5 cm (sensitivity 88.4%, specificity 60.5%)
in women.
