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CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 4, July/August 2017
232
AFRICA
opportunity to better appreciate radiation doses and use of best
practices to reduce radiation among patients undergoing nuclear
cardiology procedures on the African continent, and how Africa
compares to the rest of the world in terms of patient dose and
best-practice adherence.
Analysis of data from INCAPS revealed that overall radiation
dose to patients undergoing a procedure in Africa was similar to
that among patients undergoing a procedure elsewhere in the
world. Notably, African laboratories performed much better
than the rest of the world with regard to best-practice adherence
to minimise patient dose, as reflected in both a higher QI score
and proportion of laboratories adhering to each best practice.
However significant variation in ED and QI score was noted
within Africa, specifically at the laboratory level.
The eight-fold range in median patient ED at the laboratory
level is likely attributable to protocol use, specifically the practice
of stress-only imaging. While this practice was used in the
majority of African laboratories, the rate of use was higher in
some than others. One laboratory in particular used a stress-only
protocol in 73% of its cases and had the lowest median ED, and
incidentally, the highest patient volume.
The option of stress-only protocol could be a consequence of
a few factors: the desire to lower radiation dose, the overload of
patients due to insufficient nuclear cardiology facilities inducing a
long waiting list, and/or for economic reasons to reduce the cost of
MPI. But regardless of the laboratory’s motivation to commonly
use a stress-only protocol, its salutary effect on radiation dose is
undeniable. By contrast, the laboratory with the highest mean ED
used a stress-only protocol in only 1.7% of cases.
However while a practice of stress-only imaging is desirable
where indicated, the correct rate is determined by the disease rate
in the imaged population. Therefore it is difficult to determine
the extent to which the observed rates of stress-only use reflect
over- or under-use of this protocol, or of MPI imaging more
generally.
Overall there was good adherence in the use of specified best
practices among the observed African laboratories. However,
in contrast with the results of the worldwide study, there is a
seemingly poor correlation between laboratory adherence to best
practices and mean patient ED in Africa. Surprisingly, the two
laboratories that adhered to all eight best practices were among
the laboratories with the highest patient ED on the continent.
These laboratories predominantly used two-day protocols, with
rest imaging performed on the second day, a fact that might
explain the relatively higher rates of stress-only use in these
laboratories (29.6 and 38.5%), compared to other observed
laboratories in INCAPS. This suggests that dose-minimisation
strategies are not strictly limited to the best practices described.
Likewise, adherence to a best practice as we have defined
it does not mean it is optimally applied in the laboratory.
For example, a laboratory might use a high-efficiency solid-
state SPECT camera for every case, but may never use prone
positioning (both camera-based dose-reduction strategies).
Laboratories should continue to be vigilant in ensuring that
patient doses are optimised, given the high doses involved in the
MPI study. Still, the lack of complete adherence to best practices
among the majority of laboratories suggests opportunity to
further reduce patient EDs through those practices specified
by the expert committee. Furthermore this should be possible
Table 3. African laboratory patient volume,
radiation exposure and quality index score
Laboratory
No of
patients
Effective dose (mSv) Quality index
(QI) score
25% Median 75%
Algeria 1
42
5
8.4
9.5
7
Algeria 2
73
1.8
2
6.2
7
Algeria 3
17
2.5
4.5
5.1
7
Algeria 4
14
11.3 11.9 12.5
6
Egypt 1
54
8.2 16.3 17.2
8
Egypt 2
39
7.3 15.3 16
8
Kenya 1
5
11.4 11.6 11.8
4
Senegal 1
4
6.3
8
8.9
5
South Africa 1
12
9.4
9.4
9.4
5
South Africa 2
60
14.8 16.1 17.8
6
Tunisia 1
21
8.2
9.4
9.9
7
Tunisia 2
7
3.1
3.6
9
6
Table 4. Laboratory best-practice adherence
Best practice
Africa
(
n
=
12)
Rest of world
(
n
=
296)
p
-value
n
%
n
%
Avoid thallium stress
12 100.0 270 91.2 0.61
Avoid dual isotope
12 100.0 286 96.6 1
Avoid too much technetium 11 91.7 252 85.1 1
Avoid too much thallium 12 100.0 294 99.3 1
Perform stress-only imaging
8 66.7 85 28.7 0.005
Use camera-based dose-
reduction strategies
8 66.7 198 66.9 1
Weight-based dosing for
technetium
6 50.0 82 27.7 0.108
Avoid shine through
7 58.3 129 43.6 0.313
Table 2. Patient and laboratory demographics
and clinical characteristics
Patients
Africa
(
n
=
348)
Rest of world
(
n
=
7 563)
p
-value
Female,
n
(%)
135 (38.8)
3119 (41.2)
0.36
Age (years)
Mean
60.2
64.3
<
0.0001
SD
11
12
Effective dose (mSv)
Median
9.1
10.3
0.14
IQR
5.1–15.6
6.8–12.6
Range
1.8–20.0
0.75–35.6
≤
9 mSv,
n
(%)
173 (49.7)
2892 (38.2)
<
0.001
Stress-only,
n
(%)
109 (31.3)
896 (11.8)
<
0.001
PET,
n
(%)
6 (1.7)
465 (6.1)
<
0.001
Laboratories
12
296
Patients/laboratories
Median
19
16
0.402
IQR
10–48
8–33
Range
4–73
1–250
Quality index score
≥
6,
n
(%)
9 (75.0)
133 (44.9)
0.041
Mean
6.3
5.4
0.013
SD
1.2
1.3
Laboratories with median
dose
≤
9 mSv,
n
(%)
5 (41.7)
86 (29.1)
0.35
SD, standard deviation; IQR, interquartile range.