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Scientific Comments
Rev Bras Hematol Hemoter. 2012;34(5):323-33
Anemia and the Blood Donor
The World Health Organization recommends a collection rate of 10-20 whole blood
units per 1000 inhabitants to address transfusion needs
(1)
. However, demand for blood is
ever-increasing as medicine continuous to develop
(2)
.
Donor selection is critical to blood transfusion safety and blood donor eligibility
policies are designed to protect both the donor and the recipient
(1,3)
. Donors with relatively
low hemoglobin (Hb) levels are not allowed to donate to prevent them from developing iron
deficiency anemia (IDA). In addition, deferral of these donors guarantees that blood units for
transfusion meet the required standards for Hb content
(4)
.
Deferral for low Hb accounts for 35% to 75% of total deferrals, with the vast majority
occurring in women
(5-7)
.At the NewYork Blood Center, 92.7% of these deferrals were women
(6,7)
.
Iron deficiency is the world’s most widespread nutritional disorder, affecting both
industrialized and developing countries
(8)
. In Brazil, there are no consistent studies to show the
real problem, although some studies showed 25% of anemia in women of childbearing age
(9,10)
.
On the other hand, because IDA is the last stage of iron-deficiency, Hb measurement
alone is inadequate to detect blood donors with iron deficiency but without anemia. Recent
publications have suggested that serum ferritin levels could be a reliable indicator for body
iron stores since they provide a determination of iron deficiency at an early stage
(11,12)
.
As ferritin testing is comparatively costly, various red blood cell (RBC) parameters have
been proposed as markers for low ferritin/iron depletion
(13)
. Significant correlations between
ferritin and RBC parameters were shown in these analyses, but no study has determined which
marker is the most useful to identify donors at risk of developing anemia
(13)
.
Beta-thalassemia trait (BTT) is the second most common cause of microcytic anemia and,
for this reason, the possibility of this disease must be discarded when anemia or microcytosis
is present
(12,14)
. An interesting paper by Tiwari et al.
(14)
suggested that it could be useful to
routinely perform a complete blood count (CBC) for all blood donors and further analyze the
microcytic samples for ferritin and Hemoglobin A
2
to differentiate between IDA and BTT.
This approach, however, is relevant only in areas where there is an elevated prevalence of
BTT. These authors, also, reviewed nine indices to differentiate IDA and BTT. (Table 1)
Maria Stella Figueiredo
Universidade Federal de São Paulo –
UNIFESP, São Paulo, SP, Brazil
Conflict-of-interest disclosure:
The author declares no competing financial
interest
Submitted: 8/28/2011
Accepted: 9/5/2012
Corresponding author:
Maria Stella Figueiredo
Disciplina de Hematologia e Hemoterapia -
Escola Paulista de Medicina - UNIFESP
Rua Dr Diogo de Faria, 824, 3º andar
Vila Clementino 04037-002 -
São Paulo, SP, Brazil
stella@hemato.epm.br
www.rbhh.org or www.scielo.br/rbhh
DOI: 10.5581/1516-8484.20120085
Table 1 - Formulae and cut-off point of nine indices to differentiate iron deficiency
anemia (IDA) and beta-thalassemia trait (BTT)
(14)
Index
Formula
In favor of
IDA
BTT
RBC
x 10
9
/μL
< 5
> 5
RDW
%
> 14
< 14
Mentzer
MCV/RBC
> 13
< 13
Shine and Lal
MCV
2
x MCH x 0.01
> 1530
< 1530
England and Fraser
MCV – RBC – (5 Hb) – 3.4
Positive
Negative
Srivastava
MCH/RBC
> 3.8
< 3.8
Green and King
MCV
2
x RDW/100 x Hb
> 65
< 65
RDW index
MCV x RDW/RBC
> 220
< 220
Ricerca
RDW/RBC
> 4.4
< 4.4
RBC: Red blood cells; RDW: Red blood cell distribution width; MCV: Mean corpuscular volume;
MCH: Mean corpuscular hemoglobin
In order to fulfill their necessities, blood centers have long recognized that it is more
effective and less expensive to collect blood from existing donors than to recruit new donors
and in the United States, 71% of donors are repeat donors. But, this strategy has come at a
price: iron depletion of these donors
(5)
. After donation of 450 mL of blood, a male donor loses
242 ± 17 mg and a female 217 ± 11 mg of iron
(5,15)
. Since the 1970s, various investigators
documented the decrease in serum ferritin levels in association with blood donation
(5,11,13,16-18)
.