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Improved Screening of Donor's Blood for Malaria:
A Qatari Experience
Amer A., Al Malki
A., Yousef B., Al Mutawa H.
Division of Hematology and Blood Bank,
Department of Laboratory Medicine and Pathology
Hamad Medical Corporation, Doha, Qatar
  Abstract:
Malaria is one of
the most widespread infections globally and is
undoubtedly responsible for the majority of all
cases of transfusion-transmitted disease in the
world. Qatar is free from endemic malaria.
However, cases are seen with the large
expatriate work force imported from malarious
areas. These constitute a significant percent of
the blood donors’ pool (34%). Over a 27-month
period, among 5845 volunteers tested for
malaria, 21 were deferred (0.36%) showing
positive result when screened by the Giemsa-stained
thick smear technique, with 2 undiagnosed cases
that led to transfusion-transmitted malaria.
Since then and for the last 21 months, the
Falciparum-Spot immunofluorescence (IF) test was
implemented in an attempt to ensure accurate
screening. Among 6367 donors tested, 274 (4.3%)
were deferred. Careful questioning about donor
travel history, expansion of deferral policy and
the use of a more sensitive screening test have
all resulted in increasing layers of safety
where no transfusion-transmitted malaria was
reported in the last 21 months. These measures
were necessary to regain the trust of the public
in the safety and stewardship of the blood
supply.
 Introduction:
Transfusion-transmitted malaria is one of the
dreaded threats to the safety of transfusion
services in this malaria endemic world. Qatar is
free from malaria. Imported cases are however
seen as the country continues to employ a large
expatriate work force from malarious countries (1).
The concept of a global village with the speed
and ease of international travel has also added
to the problem allowing a potential blood-born
infectious agent present in any region of the
world to travel freely from one pole of the
globe to the other in a matter of hours. This
has led to increased concern with transfusion
risk of malaria(2).
Transfusion-associated malaria is often severe
and even fatal because diagnosis is frequently
delayed and it complicates an already serious
underlying disorder. Policies for preventing
malaria transmission by blood transfusion rely
on a multi-layer system of safety. Sensitive
screening tests are necessary but represent only
one component. Other layers of safety include
detailed donor education, stringent screening,
selection and deferral procedures, post donation
product quarantine and donor tracing and
notification when instances of any infectious
agents occur. Each element plays a role in
preventing tainted units from entering the blood
inventory(3).
In some areas of the world, in U.S.A. for
instance, donors’ questionnaire was only relied
on, although the necessity for reviewing donor
screening process has recently emerged(4).
One hundred years
ago, Giemsa-stained thick smears were adopted
for the first time for malaria diagnosis and
still continues to be the method of choice in
most malarious countries, although in the recent
past, several alternatives have been developed
that exhibit some advantages(5).
We herewith report our experience over a period
of 48 months in our struggle for a malaria free
blood supply.
Materials
and Methods
Giemsa stained
thick smears used to be our test of choice for
screening donors’ blood for malaria. However, after
the occurrence of 2 blood transfusion-transmitted
malaria cases, and since April 2002, we decided to
shift to the Falciparum-Spot immunofluorescence test
(BioMerieux®, France). The test was applied
following the manufacturer’s instructions.
Non-specific fluorescence of the parasite was
avoided by preliminary absorption of the test serum
with group A1 erythrocytes. Screening for malaria
included those donors who have traveled in the
previous 6 months to an endemic area or those
emigrants who re-visited endemic areas in the
previous year and those who have had antimalarial
treatment in the previous year. We compared the
screening results during the period from April 2002
till December 2003 (21 months), with those seen in
the preceding 27 months when Giemsa-stained smears
were used (from Janua-ry 2000 till March 2002).
Results
The total
donors’ pool/year ranges from 10,468 to
12,151 with a mean±SD of 11,564.7±758.1
donors/year (Table 1). Donors
form malarious areas constitute a
significant proportion (35.3%) (Figure
1). During the 27-month period, a
total of 5845 were tested, in whom 21
positive cases were detected (0.36%). In the
next 21-month period, 6367 cases were tested
with IF technique and 274 cases were
positive (4.3%) (p<0.0005) (Figure 2).
Positive blood was excluded from the
blood inventory and the donors notified and
deferred.
Table 1:
Donors' numbers and distribution
over a 48-Month period (From
2000-2003)
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Discussion:
There are currently no FDA approved assays for
screening blood donors for Malaria(2,
6), and so far, all suggested protocols
are based on individual recommendations reported
from various endemic and non-endemic areas of
the world. In our experience, since April 2002
when the IF-spot test was introduced in the
blood bank for screening blood donors, no
transfusion-transmitted malaria case was
reported compared to the previous era when
Giemsa-stained thick smear technique was used,
reflecting a better sensitivity of the test.
Several conclusions in favor of the IF-spot test
were reported in various parts of the world
suggesting that the IF assay is by far the most
reliable test for use in malaria serodiagnosis(7,
8, 9), whereas others preferred combining
malaria antigen and antibody detection to confer
a better screening(10).
The use of PCR was also reported as a valuable
tool(11)
especially in low-level parasitaemia(12).
In our experience, the use of IF spot test seems
so far quite convenient having 98.7% specificity
and 98% sensitivity in providing a retrospective
confirmation of an attack of malaria(7).
A
risk still exists especially in low parasite
load. The fact that partial immunity can extend
the incubation period is also of concern. The
unexceptionally long incubation periods of some
vivax strains reaching up to 250-637 days(13,
14) also constitutes an insisting threat.
The limited donors’ pool stands as a stubborn
obstacle against expansion of the deferral
policies. It should also be born in mind that
the quest to eliminate potential risky blood
donors and the solitary dependence on malarial
antibody detection as a screening test might
lead to the loss of many healthy donors thus
further reducing the blood pool. In our opinion,
combining IF antibody test with antigen
detection would probably help overcome this
problem. The cost-effectiveness of such protocol
should however be evaluated locally prior to its
implementation.
New and innovative methods of malaria diagnosis
should be developed. Concurrently, the World
Health Organization has opened a dialogue with
scientists, clinicians and manufacturers on the
realistic possibilities for developing accurate,
sensitive and cost-effective rapid diagnostic
tests for malaria(15).
Other promising technological approaches to
blood safety include pathogen inactivation in
cellular components(8).
Until this is achieved, a high index of
suspicion should be maintained in those with
suggestive travel history. Formulation and
updating of appropriate donor selection policies
should help reduce the incidence of
transfusion-transmitted disease.
The need for a safe blood supply constitutes a
never-ending struggle for man. The slogan used
by the American National Red Cross blood program
rightfully refers to blood as the “Gift of
Life”. Like many good things, it comes with
risks.
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