CARDIOVASCULAR JOURNAL OF AFRICA • Vol 23, No 4, May 2012
188
AFRICA
cTnT levels (25.07
±
8.01 vs 19.06
±
8.57,
p
=
0.026). According
to ROC analysis, an APACHE score of more than 20.5 indicated
a positive cTnT with 66.7% sensitivity and 62.1% specificity.
An APACHE II score higher than 25.5 indicated a positive cTnT
with 50% sensitivity and 83% specificity (
p
=
0.006, area under
the curve
=
0.712 and standard error
=
0.072) (Table 2, Fig. 1).
Serial blood sampling for cTnT levels was done in the first
24 hours, and on the fourth, seventh and 10th day after ICU
admission (Fig. 2). No significant difference was seen in the
changes in troponin levels between deceased and discharged
patients (
p
=
0.4). This difference was also non-significant when
different diseases were evaluated separately. The difference
between troponin levels was not significant between deceased
and discharged patients (
p
>
0.05).
The outcome was significantly different with regard to
normal or elevated cTnT concentrations on the first and seventh
days after admission (Table 3) but there was a non-significant
difference between patients with different levels of cTnT on
the fourth and 10th days of admission (Table 3). The cTnT
concentration was not significantly different between deceased
and discharged patients (Table 4).
There was a significant association between patients’ outcome
and change in cTnT levels in the first and fourth days after
admission using chi-square analysis (
p
=
0.029). All patients
with a reduced cTnT level died, whereas all patients with an
increased cTnT level survived. Also a significant relationship
was found between the outcome of patients and the level of
cTnT on the fourth and the seventh days of ICU stay (
p
=
0.02).
All patients with an elevated cTnT level from the fourth to the
seventh day survived, whereas all patients with a decreased cTnT
level from the fourth to the seventh day died.
The survival rate of patients on the fourth, seventh and 10th
days after admission was 87, 74 and 72% in normal patients,
and 83, 61 and 56% in patients with elevated cTnT levels,
respectively. The estimated mean survival time of patients with
elevated cTnT levels on admission was 16.77 (SE
=
3.38) days,
and it was significantly lower than the group with normal levels
on admission, with a mean survival time of 26.08 (SE
=
3.15)
days (
p
=
0.027). This difference was also significant for cTnT
concentration on the seventh day after admission [mean survival
31.6 (SE
=
3.6) days in patients with normal cTnT levels vs 19.7
(SE
=
2.5) days in patients with elevated cTnT levels,
p
=
0.012]
(Fig. 3A, B).
Discussion
The present study shows that in critically ill patients, elevated
cTnT levels were significantly associated with increased
mortality, and the survival time was significantly shorter in
patients with elevated cTnT than in those with normal cTnT
levels.
TABLE 2. THE RESULTS OF ROCANALYSIS
APACHE score
Sensitivity
Specificity
18.5
0.684
0.552
19.5
0.684
0.603
20.5
0.684
0.621
21.5
0.632
0.655
22.5
0.526
0.69
23.5
0.526
0.741
24.5
0.526
0.793
25.5
0.526
0.828
27
0.474
0.879
28.5
0.368
0.897
The italicised rows are suggested as the best points to predict cTnT.
TABLE 3. MORTALITY RATE BASED ON NORMAL OR
ELEVATED cTnT CONCENTRATION IN DIFFERENT
MEASUREMENTS
cTnT concentration
(
µ
g/l)
Deceased
n
(%)
p
-value
cTnT-1
on the 1st day
<
0.1
33 (40)
0.03
>
0.1
19 (63)
cTnT-2
on the 4th day
<
0.1
29 (53)
0.69
>
0.1
11 (58)
cTnT-3
on the 7th day
<
0.1
18 (44)
0.024
>
0.1
13 (65)
cTnT-4
on the 10th day
<
0.1
16 (57)
0.78
>
0.1
5 (62)
Fig. 1. The results of ROC analysis (area under the curve
=
0.712 and standard error
=
0.072).
1.0
0.8
0.6
0.4
0.2
0.0
Sensitivity
0.0
0.2
0.4
0.6
0.8
1.0
Specificity
ROC curve
Fig. 2. Trend in cTnT levels over four time periods for 25
patients (
±
SD).
0.12
0.10
0.8
0.6
0.4
0.2
0.0
Means of cTnt
1st
4th
7th
10th
Day of measurment
died
discharged
Outcome
TABLE 4. cTnT CONCENTRATION IN DECEASED OR
DISCHARGED PATIENTS
Deceased
(
µ
g/l, mean
±
SD)
Discharged
(
µ
g/l , mean
±
SD)
p
-value
1st day
0.042
±
0.061
0.03
±
0.084
0.4
4th day
0.103
±
0.277
0.028
±
0.066
0.12
7th day
0.094
±
0.25
0.852
±
0.175
0.86
10th day
0.121
±
0.365
0.053
±
0.119
0.42
