58 / 74
CARDIOVASCULAR JOURNAL OF AFRICA • Volume 28, No 5, September/October 2017
332
AFRICA
The historical cut-off points put forward by the World
Health Organisation (WHO), namely a haemoglobin (Hb)
concentration
<
13 g/dl for men or
<
12 g/dl for women have been
under debate regarding their relevance when it comes to SSA,
where haemoglobin values have been reported to be relatively
low in the normal general population.
6,7
This difference might be
related to a high prevalence of infections, haemoglobinopathies
and nutritional deficiencies. Furthermore, genetic factors may
also be implicated.
6,7
In SSA, the concept of clinically relevant
Hb cut-off points has been applied in some settings, leading to
the use of more stringent cut-offs when reporting anaemia in HF
in SSA compared to studies from high-income countries.
2,8
For example, a Hb cut-off value of
<
10 g/dl in HF for
both genders was used in the Tanzania Heart Failure (TaHeF)
study,
2
the SSA Survey of Heart Failure (THESUS) study,
8
and
by Ogah
et al
.,
9
while in the Heart of Soweto,
10
a cut-off value
of
<
11 g/dl for men and
<
10 g/dl for women was defined as
clinically relevant anaemia (Table 1). This further complicates
the comparability and potential criteria for interventions versus
what has already been reported from high-income countries.
Accordingly, there is a need for standardised and uniform cut-off
points that are relevant to and applicable in SSA.
Epidemiological gap in knowledge of anaemia
burden in HF in SSA
The available data suggest that there are limited reports about the
epidemiology of anaemia in SSA compared to a large number of
studies in high-income countries. Using the WHO cut-off point,
the small amount of scattered information available reveals that
the prevalence of anaemia in HF in SSA ranges from 14 to 64%
(45% on average) (Table 1), compared to 36% in the general
population. In high-income countries, the prevalence ranges
from 10 to 49% (34% on average), compared to 8% in the general
population.
11,12
Higher rates of prevalence are therefore seen in SSA than in
high-income countries, and in both populations, the prevalence
of anaemia in HF is higher than the global burden of anaemia
in the general population. Less attention is paid by clinicians in
SSA to screening for anaemia in HF in a clinical perspective,
which may be explained by the scarcity of epidemiological data.
As far as interventions are concerned, there are no clinical
trials in SSA that provide guidance on the appropriate approach
to manage anaemia in HF. Due to the relatively recent attention
given to the importance of iron deficiency in HF in SSA,
guidelines do not provide help in this regard. Studies are therefore
needed to provide more insight into the burden, peculiarities and
possible interventions for anaemia in HF in SSA.
Epidemiological gap in knowledge of ID
burden in HF
The prevalence of ID in HF populations in SSA is largely
unknown. To our knowledge the TaHeF study, reporting a
prevalence of 67%, was the only study providing data on the
prevalence of ID in HF in SSA.
2
This should be seen in the
perspective of more than 12 studies from high-income countries
(Table 2). Since the only study so far conducted indicates that
iron-deficiency anaemia is a very common condition in SSA,
further studies should aim to see whether active detection and
correction of ID are warranted.
Challenges in biochemical diagnosis of ID in HF
Absolute ID is conventionally defined by a serum ferritin
level of
<
30 mg/l.
29,30
As the ferritin is elevated in HF due to
the inflammatory state, in their 2012 guidelines, the European
Society of Cardiology introduced the definition of ID in HF as
either serum ferritin
<
100 mg/l for absolute ID or 100–299 mg/l
and transferrin saturation
<
20% for functional ID.
31
The criteria
have been used in several clinical trials.
32-34
These diagnostic
criteria for ID in HF used in high-income countries may not be
feasible in SSA due to the lack of diagnostic facilities and the
presence of co-existing malnutrition, haemoglobinopathies and
infections.
Serum ferritin/transferrin saturation (TSAT) has commonly
been used in several observational and clinical trials (Table 2) to
Table 1. Studies in SSA reporting on adult HF patients with anaemia
Authors, country and year
Sample
size
Anaemia
(%)
Definition of anaemia by
haemoglobin (g/dl) or
packed cell volume (%)
Makubi
et al.
2
Tanzania, 2015
Ogah
et al
.
9
Nigeria, 2014
452
8.8
<
10
Damasceno
et al.
8
9 African
countries, 2012
1006
15.2
<
10
Stewart
et al
.
10
South Africa,
2008.
699
10.0
Male
<
11, female
<
10
Karaye
et al.
13
Nigeria, 2008
79
41
<
39% in male and
<
36%
in female
Kuule
et al
.
14
Uganda, 2009
157
64.3 Male ≤ 12.9, female ≤ 11.9
Inglis
et al.
15
South Africa,
2007
163
13.5 World Health Organisation
Dzudie
et al.
16
Cameroon
,
2008
140
15.7
Not available
Oyoo
et al
.
17
Kenya, 1999
91
13.2
Not available
Ojji
et al
.
18
Nigeria, 2013
475
8.0
Not available
Onwuchekwa
et al.
19
Nigeria,
2009
423
6.2
Not available
Table 2. Studies reporting on the magnitude of ID in HF
Authors, country and year
Number
% with
ID
Definition of ID
Makubi
et al.
2
Tanzania, 2014 411
67
MCV
<
80 fl
Jankowska
et al
.
20
Poland,
2014
165
37 Low hepcidin and high sTfR
Serum ferritin and TSAT
Rangel
et al
.
3
Portugal, 2014
127
36
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
Parikh
et al
.
21
United States,
2014
574
61
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
Enjuanes
et al.
22
Europe, 2014 1278
58
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
Ijsbrand
et al
.
4
Europe, 2014
1506
50
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
Jankowska
et al.
23
Poland,
2013
443
35
SF
<
100
µ
g/l OR SF
100–300
µ
g/l +TSAT
<
20%
Nanas
et al
.
24
Greece, 2006
37
73
Bone marrow
Cohen-Solal
et al
.
25
France,
2014
832
72
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
Yeo
et al
.
26
Singapore, 2014
751
61
SF
<
100
µ
g/l OR SF
100–299
µ
g/l +TSAT
<
20%
De Silva
et al.
27
UK, 2006
955
29 Lower limit for serum iron
and SF
Klaus
et al
.
28
UK, 2004
296
14
Low SF
sTfR: soluble transferrin receptor, TSAT: transferrin saturation, SF: serum
ferritin, TR: transferrin receptor.